Loading-Offloading Buoy for CNG Operations

The present invention relates to loading and offloading buoys for gaseous substances, such as natural gas, and preferably for compressed natural gas (CNG) operations, such as for use in the loading or unloading of CNG prior to the distribution or transportation of the natural gas on ships or barges.

The present invention provides an apparatus, a system and a method for loading gas on the ships or barges, whereupon it can be stored or transported thereon. It also provides an apparatus, a system and a method for offloading the gas from the ships or barges at a delivery point. In particular, the present invention relates to an apparatus, a system and a method for loading, transporting and offloading natural gas in the form of Compressed Natural Gas (CNG) on and from one or more ships or barges.

Hereinafter, the term "ship" or "ships" will be used to include both ship(s), e.g. self-powered ship(s), and barge(s), e.g. unpowered, or towed, barge(s), and other forms of boat or sea-faring vessel on which such gas might be stored, distributed or transported.

Natural gas sourced offshore from underwater natural gas wells can be transported by carrier ships as an alternative to transportation using pipelines, whether land based or underwater. One manner of transporting natural gas is in the form of Liquid Natural Gas (LNG). Another form of transportation is Compressed Natural Gas (CNG).

With LNG, it is necessary to cool the gas down to very low temperatures in order to liquefy the gas. The gas is then re-gasified prior to delivery. Moderate pressures are involved in storing LNG in tanks on the ships during transportation, e.g. 20 bar or less. With CNG, the gas is instead simply compressed to high pressures, of the order of hundreds of bars - typically to a pressure in the order of 250bar or more, and then transported inside suitable pressure vessels, such as steel or composite pressure vessels, on the ships. The gas is then allowed to expand at the delivery point, so that it can be delivered at a lower delivery pressure - typically below 30bar.

Existing naval CNG transportation systems and their methods of loading or offloading are known to have some disadvantages, such as a) low loading and unloading efficiencies (the loading and unloading efficiency is quantified by the ratio between the total energy or mass of CNG delivered at the delivery point by the ship, to the total energy or mass of CNG loaded at the loading point in the ship); b) risks connected with either the formation of hydrates upon delivery in the delivered CNG, which can lead to, or which can be a result of, a poorer product (i.e. a natural gas with a lower calorific value), and/or the formation of ice, which is known to be able to cause structural damage to the CNG delivery equipment. It is desireable to improve upon these systems.

Further, there is a desire for increased capacity and efficiency in the field of fuel, and it would be desireable to carry this through also to Compressed Natural Gas (CNG) transportation by allowing additional storage capacity for a given storage volume. Increased pressures or reduced temperatures are recognised to be the proposed solutions for this. However, for the most common steel-based cylinders, this has led to the development of thicker structures, which usually require stricter quality control over defects and structural irregularities, especially in corrosive environments, or more complex cooling/refrigeration systems, and thus larger ships for carrying the increased mass resulting therefrom. Given that typically the pressure vessels' mass greatly, or their mass plus the mass of the ancillary equipment, significantly exceeds the mass of the CNG contained therein, the resulting increased equipment or carriage costs tend to increase per unit delivery volume of CNG, and thus the overall efficiencies tend actually to decrease as the pressure or temperatures are adapted for increasing delivery volumes. Further, the existing delivery equipment for loading or offloading are not designed for these altered temperatures or pressures, whereby they too need to be adapted, with the resultant costs of that also changing the equation. Achieving these improvements without increased inefficiencies would thus also be desireable.

The exploitation of stranded gas reserves has also lead to the necessity of reducing facilities and treatments at remote loading and offloading sites to enable those facilities to be economically viable, and yet still be able to sustain the environmental conditions at thosse locations. CNG is not developed in this sector. For CNG, however, the present inventors note that subsequent processing or cleaning of the fluid could instead be carried out further down the delivery chain, prior to subsequent redistribution yet further down the delivery chain. The down side of this requirement, however, is the possible presence of condensates and hydrates in the transported fluid, making the containment materials requirements for both the pressure vessels and the remote and later delivery equipment, such as the pipework at the remote loading and offloading sites, higher in terms of corrosion and damage resistance. The present invention looks to alleviate these problems.

Furthermore, in the case of large reserves the use of CNG is penalized due to its relatively lower fuel storage density compared to Liquified Natural Gas (LNG): approximately 0.2 kg/cm3 of CNG at 200 bar and ambient temperature vs. 0.4 kg/cm3 of LNG, albeit at -162 °C (cryogenic liquid). Improving upon this would be desireable.

Two methods to achieve higher gas densities and therefore improve the amount of transported gas within a given storage volume, are discussed briefly above - higher pressures and lower temperatures, but these to date only can be achieved using thicker and heavier containment structures, or a more complex implementation of the process facilities - to refrigerate and possibly liquefying the fluid. The present invention looks to improve upon this.

It is also to be appreciated that CNG loading and offloading procedures and facilities depend on several factors linked to the locations of gas sources and the composition of the gas concerned. With respect to facilities for connecting to ships

(buoys, platform, jetty, etc ..) it is desirable to increase flexibility and minimize infrastructure costs. Typically, the selection of which facility to use is made taking the following criteria into consideration:

• safety;

· reliability and regularity;

• water depth and movement characteristics; and

• ship operation: proximity and maneuvering.

A typical platform comprises an infrastructure for collecting the gas which is connected with the seabed. A jetty is another typical solution for connecting to ships (loading or offloading) which finds particular application when the gas source is onshore or close to the shoreline. From a treatment plant, where gas is treated and compressed to suitable loading pressure as CNG, a gas pipeline extends to the jetty and is used for loading and offloading operations. A mechanical arm extends from the jetty to a ship. Mechanical arms can also extend from platforms, whether floating or otherwise.

Jetties are a relatively well-established solution. However, building a new jetty is expensive and time-intensive. Jetties also require a significant amount of space and have a relatively high environmental impact, specifically in protected areas and for marine traffic. Platforms can be floading or fixed. Jetties likewise can have a floating or fixed end. If floating, often they are relatively secured in the transverse direction, e.g. by legs that are fixed to the bed, but they might float up and down on those legs e.g. to allow for varying tides and sea conditions.

Other solutions include those that utilize buoys or the like, and they can roughly be categorized as follows:

• CALM buoy system;

• STL systems;

• SLS systems; and

· SAL systems.

A Catenary Anchor Leg Mooring (CALM) buoy is particularly suitable for shallow water. The system is based on having the ship moor to a buoy floating on the surface of the water. The main components of the system are: a buoy with an integrated turret, a swivel, piping, utilities, one or more hoses, hawsers for connecting to the ship, and a mooring system including chains and anchors connecting to the seabed. The system also comprises a flexible riser connected to the seabed. This type of buoy requires the support of an auxiliary/service vessel for connecting the hawser and piping to the ship.

A Submerged Turret Loading System (STL) instead comprises a connection and disconnection device that is typically better for rough sea conditions. The system is based on a floating buoy moored to the seabed (the buoy will float in an equilibrium position below the sea surface ready for the connection). When connecting to a ship, the buoy is pulled up and secured to a mating cone inside the ship. The connection allows free rotation of the ship hull around the buoy turret. The system also comprises a flexible riser connected to the seabed, but requires dedicated spaces inside the ship to allow the connection.

A Submerged Loading System (SLS) is another form of buoy-type arrangement and it typically consists of a seabed mounted swivel system connected to a loading/offloading riser and acoustic transponders. The connection of the floating hose can be performed easily without a support vessel. By means of a pick up rope the flexible riser can be lifted and then connected to a corresponding connector on the ship.

A Single Anchor Loading (SAL) system if a fourth type of buoy arrangement and it typically comprises a mooring and a fluid swivel with a single mooring line, a flexible riser for fluid transfer and a single anchor for anchoring to the seabed. A tanker is connected to the system by pulling the mooring line and the riser together from the seabed and up towards the vessel. Then the mooring line is secured and the riser is connected to the vessel.

Although these systems can provide a workable mode of operation, it would be desirable to improve the loading/unloading efficiency of these various forms of equipment so that the loading/unloading efficiency of the ships can also be increased. It is also desireable to provide less costly and/or longer lasting loading or unloading equipment. In particular, it would also be desireable to provide loading or unloading equipment that can load pressure vessels in ships to increased pressures to those of the art, such as pressures in excess of 350 bar, and potentially to pressures as high as 700 bar or more preferably up to or in excess of 1000 bar. Such equipment currently is not known from the art, even though pressure vessels suitable for storing fuel at pressures in excess of 1000 bar are envisaged as being possible using composites or steel. Bear in nind though that such pressure vessels have not been commercialised since they would be extremely heavy due to the increased wall thicknesses.

According to a first aspect of the present invention there is provided a buoy system for loading natural gas from a gas well to a ship, wherein the gas is compressed by a compressor of the buoy system, prior to loading, to a transportation pressure in the hundreds of bar, i.e. a high operating pressure. The pressure will be 200 bar or in excess of 200 bar. Preferably it is 230bar or greater.

According to a second aspect of the present invention there is provided a buoy system for offloading natural gas from a ship to a gas delivery network, wherein the gas is stored on the ship, and offloaded therefrom, at a transportation pressure in the hundreds of bar, i.e. a high operating pressure. The pressure will be 200 bar or in excess of 200 bar. Preferably it is 230bar or greater.

Preferably the buoy system of the first aspect of the present invention is integrated into a common system to the second aspect of the present invention.

Preferably the operating pressure used in one of both of the aspects of the present invention is in excess of 250 bar, in excess of 350 bar, in excess of 700 bar or in excess of 1000 bar.

Preferably the buoy system is one of a CALM buoy system, a STL system, a SLS systems or a SAL system.

The system preferably comprises an offshore wave energy converter (OWEC), e.g. for driving the compressor, or for powering other components of the system. The system may comprise an energy storage device for storing excess energy from the OWEC. Preferably that device is arranged to transfer excess energy to the shore, or to a ship, e.g. to a ship when the main gas offloading or loading buoy is connected to the ship, or both.

The present invention also provides a buoy system for at least one of a) loading natural gas from a gas well to a ship or b) offloading natural gas from a ship to a gas delivery network, the buoy system comprising one or more offshore wave energy converter (OWEC) such that the buoy system is able to gather and store wave energy to be used during the relavant one or both of loading or offloading practices.

The OWEC of this, or the previous, aspect of the invention preferably comprises a linear generator.

The OWEC of this, or the previous, aspect of the invention preferably comprises a float of neutral buoyancy located above a generator component of the OWEC, but below a floating buoy of the OWEC.

The OWEC of this, or the previous, aspect of the invention preferably comprises a generator comprising a stator and a translator for movement relative to the stator as the OWEC experiences wave energy. Preferably that movement is linear with the translator being fixed relatively below a float of neutral buoyancy located above the generator of the OWEC.

Preferably the float is a sphere.

Preferably springs are located at the extremes of travel of the translator. Preferably those extremes are located at a top and bottom of the generator.

The present invention also provides a buoy system comprising a buoy at or near the water's surface and a subsea piping manifold at or near the seabed, wherein a riser connecting the buoy to the subsea piping manifold comprises a composite or hybrid pipe along at least a portion of its length. Preferably the composite pipe forms or is part of a composite pipework, the composite pipework extending along at least 80% of the length of the riser. The pipe or the pipework may comprise or be a hybrid pipe as discussed below.

The present invention also provides a gas loading or offloading system comprising, respectively, at least one loading or offloading arm, the arm having a pipe therein, the arm or the pipe, or both, having a hybrid metal-composite structure including a composite structural over-wrap. Preferably the system has a composite pipe including an hydraulic metal liner and the composite structural over-wrap.

Preferably the pipe is a hybrid pipe as discussed below.

The system may comprise a pipe, piping or pipework that is involved in the loading/offloading activities, at least a portion of that pipe taking the form of at least one of an hybrid metal-composite structure, a cladded metal liner or a non-metallic liner wrapped with fibres.

The system may comprise a floating structure, the composite or hybrid structure being a weight acting upon that floating structure.

In accordance with this and other aspects of the present invention, the pipe, piping or pipework involved in the loading/offloading activities may include a number of pipes that have a pluality of different structures. For example there can be piping having an hybrid metal-composite structure, as already mentioned above. It can have a cladded metal liner. Alternatively, or additionally, there could be piping having a non- metallic liner wrapped with fibres where the non-metallic liner may be DCPD or HPDE. With either or both of these arrangements, or instead of those hybrid pipes, there can also be conventional metal piping, or conventional flexible high-pressure piping.

One aspect of the present invention may involve composites in a turret/arm of a buoy, platform or jetty, for loading or offloading of CNG ships. This solution is particularly beneficial when the device is on a floating structure, be that the buoy, the platform or the jetty, or on a FPSO (floating production, storage and offloading unit) since weight saving can be a key design advantage for floating structures.

The composites may be used in a tubular configuration where internal gas pressure exists, or on non-flexible portions of the loading arm, or on members having a linear symmetrical axis. These components may have a structural or non-structural liner (whether cladded carbon steel, stainless steel - or equivalent alloy, HDPE, pDCPD resins, epoxies - or equivalent low permeability polymers), which is then over-wrapped with a reinforced polymer or resin, for example one or more layer of a carbon or glass- reinforced polymer, each layer potentially being different.

In the case of a cladded layered material, the minimum thicknesses required for manufacturing (e.g. clad overlay) may lead to a load bearing liner (with piping-like reduced diameters), hence stainless or similar and polymer liners should be the preferred solution as they are "corrosion resistant" without an additional layer. Composites may also be used for supporting structures of the loading arm to further reduce the overall weight. For example, tubular-like composite structures may be used where the stresses are mostly compressive, and beam-like structures may be more suitable where the stresses are mostly flexural or tensile. Different sections known to a skilled person can also be used. It should be appreciated, however, that tubular can include circular, oval and box sections, whereas beam like structures may more commonly be T, H, I, L or box shaped.

Tubular components are ideally manufactured with the filament winding technique about a mandrel/liner. Beam components are ideally manufactured with a pultrusion technique: a process that typically consists of pulling, pushing or or extruding a continuous line of fiber reinforcement - often multiple filaments or multiple fibre rovings - through an impregnating resin bath, so as to impregnate the reinforcement as a batch, e.g. passing it under and around a roller in the base of the bath, and then combining those fibres in a die that forms them into the desired shape of the beam by having a hole of that desired cross section.

If heat curing is needed, the combined fibres can then be passing through a curing oven to consolidate the resin system, prior to cutting them to length.

In another arrangement, the die itself could be heated. This could then take the place of the curing oven, or supplement it. This is optional.

The pulling device is typically after the oven, although pulling members or pushing members can be provided elsewhere along the production line.

In addition to the weightloss, other advantages provided by such platform/turret/arm solutions are:

- easy access for maintainability;

- if a supporting platform is used, other critical equipment can be placed on the surface - there will be spare buoyancy on any given floating structure for each amount of weight saved on that structure;

- once a ship is secured, platform solutions avoid a need for dynamic positioning systems of the ship, thus saving fuel.

The present invention also provides a gas loading system comprising a compression unit and a dehydration unit, both submerged and placed on the sea bed, and connected through to a gas loading point, wherein the two submerged units are powered by wave energy. Preferably the wave energy is converted into a suitable power source by one or more local offshore wave energy converter (OWEC). The OWEC may be as defined previously. The use of wave power reduces pollution and can help to increase the efficiency of these units.

It will be appreciated from the above that the present application relates to subject matter that will benefit from the teachings of each of the following prior applications, as already filed by the present applicant: PCT/EP201 1/071802, PCT/EP201 1/071803, PCT/EP201 1/071790, and PCT/EP201 1/071806, all of which are incorporated herein in full by way of reference. The features of the inventions disclosed in those prior filings are relevant to or combinable with the present invention. For example, a feature of the present invention concerns pipework, and that pipework will benefit from being inspectable, as per PCT/EP201 1/071790. It will also benefit from being corrosion resistant or increasingly impermeable, as per PCT/EP201 1/071806. The systems of the ships loading/offloading equipment, as defined for example in PCT/EP201 1/071802 and PCT/EP201 1/071803, will also work together with the present invention to provide an improved overall solution.

By way of example, pipes are used in CNG operations to interconnect pressure vessels, or to link the vessels with CNG loading or distribution equipment.

The pressure vessels are often seen to be the core components of a CNG operation. The pipes, on the other hand, are seen to be of a standard form, and thus of only a marginal value in terms of whether they are potential targets for development. Further, the pipes are already manufactured relatively cheaply, due to the volume of pipes produced everyday, and this low cost steers companies away from spending time and money on improving their performance and physical characteristics. As a result, CNG pipe networks are predominantly built using traditional, circular, steel pipes, but of a variety of different sections, i.e. larger pipes, smaller pipes and thicker/thinner pipes, with the appropriate section being chosen for supporting a specified flow rate and/or pressure (of the CNG passing therethrough). As such, there will be high pressure sections (suited e.g. to withstand pressures from 140 to 250bar, or even 300 bar), mid pressure sections (suited e.g. to withstand pressures of between 90 and 140 bar), and low pressure sections (suited e.g. to withstand pressures of between 30 and 90 bar). Further, since the high pressure pipes are typically both heavier and more expensive than the low pressure pipes, the pipe sections do get tailored to the given application, rather than there being simply an overcautious high-pressure specification for all applications.

Each pipe network within a given application will comprise a number of preformed pipes that are connected together. This can be by welding them together, or it can be by bolting them together by means of flanges or joints. There will also be stepped joints or stepped connections where the CNG pipe network comprises pipes of different diameters or wall thickness. These too can be welded together or bolted together.

These steel (or other metal) pipes are recognised to be heavy, and thus difficult to transport. For the same reason, they are difficult to interconnect, either via welds or the bolted connections. Likewise supporting them in situ is difficult, whether clamped into a mount or secured in free-space via the end connections. These problems can be further compounded when the CNG pipework installation is located in a hostile environment, such as in off-shore locations, and can likewise give rise to buoyancy issues when located on a floating platform, jetty or ship, and their need to be corrosion resistant (e.g. due to the presence of saltwater spray within the pipework environment) is clear.

The weight of the pipework stems from the fact that the wall thickness of these metal pipes is typically relatively large. For example, in high pressure applications, i.e. those typically above 200 bar, the thickness of the wall of the pipes might be as much as 100 mm, depending on diameter and factor of safety applied. Such pipes are inevitably very heavy.

As for the issue of corrosion, the steel pipes are also known to be affected by saltwater-induced corrosion, typically on the outside thereof. However, in addition to that there can be problems with corrosion, or chemical attack, on the inside of the pipes, such as due to the toxic fluids to be found within the CNG itself. After all, CNG fluid can be highly corrosive, especially when in the form of "well stream fluid" (a non- treated or raw version of CNG), and even worse when in presence of condensed phases - they can activate and/or increase corrosion rates. This internal or external corrosion (or chemical attack) can lead to pitting, cracking and other failures or damage to the pipes, i.e. defects. For this reason stainless steel is frequently used, with the resultant increase in costs.

It is also to be observed that these defects are often hard to see, whereby they are difficult to find during inspections, even when sophisticated ultrasonic technologies are employed in these inspections. Yet further, the pipes also suffer from further problems, For example, welded joints in metallic piping networks are recognised to provide a point of weakness in the installation, and since the strength of the joint or weld is determined usually by the degree of skill or accuracy of the operators who created the welds, the degree of the weakness can be highly variable. Welding thick-walled steel pipes is also difficult, expensive and time (and energy) consuming.

The present invention therefore aims also to overcome or alleviate at least one of the above-identified disadvantages of the known steel or metal-based pipes, and of the known methods of making them, so as to develop the design of pipes in CNG applications, particularly for the loading and offloading environment.

In particular, an object of the present invention is to provide pipes for CNG applications which are lighter in weight than existing, equivalent, steel pipes, i.e. ones having the same structural capabilities (e.g. terms of flow rates or pressure handling capabilities).

The present invention also aims to eliminate or alleviate one or more of the disadvantages found in pipe joints featuring welds.

The present invention also aims to provide piping that has minimal or lower maintenance requirements for CNG applications than the steel pipes of the prior art.

The present invention also seeks to provide a pipe design that facilitates an easy inspection, preferably a visual inspection, for detecting the presence of significant or developing defects.

As for the desire to improve upon corrosion resistance, the present invention also benefits from the use of coated pipes.

In particular, the pipes may made of plastics which have an internal metallic coating, or other composite designs having an internal metallic coating, e.g. with a fibre wrap integrated within a resin body.

Metallic pipes, particularly steel pipes, are instead the current preferred choice in the art and are widespread across many industrial and trade sectors. For example, metallic pipes are extensively used in the oil and gas industry for moving fluids around from one location to another, or between machinery. Metallic pipes are generally used due to their reliable mechanical properties, including strength, durability and containment/non-porous characteristics, although they are heavy.

Plastics pipes, which are lighter than metallic pipes, are also extensively used across industrial and trade sectors. For example, thermoplastic materials such as polyethylene (PE) are commonly used for water pipes. Medium density Polyethylene (MDPE) is also being used, such as in certain limited applications in the handling of domestic natural gas. Other plastics commonly used include acrylonitrile butadiene styrene (ABS), various forms of polyvinyl chloride (PVC, including PVCu, PVCc, cPVC or Corzan®), polyproplene (PPh).

PE and MDPE pipes, along with may of the other plastic pipes mentioned above, are lightweight, cheap to make (compared to steel or copper), corrosion free and generally non-permeable to fluids, whereby they can also offer suitable containment capabilities for those limited applications. They are also relatively easy to manufacture, by being extrudable. Plastics pipes, however, typically have a lower relative stiffness and strength compared to metal pipes. Further, they can be more porous than metal pipes. As a result, they often are formed with a thicker wall-thickness than the corresponding metal pipes, to compensate for these weaknesses of plastics, whereupon they can have a smaller internal cross section for a given external diameter.

To improve the operational characteristics of metallic and plastic pipes at the interface between the pipe and the contents therefor, i.e. whatever substance is to be transported therein, various types of internal liners have been applied to prior art pipes.

For example, it is known to provide a plastic liner or coating inside a metallic pipe to prevent corrosive fluid passing through that pipe from corroding the internal walls of the metallic pipe. However, it is not known to provide an internal metallic liner or coating for plastics pipes, mainly for the following reasons:

First, it is generally difficult to coat the pipe internally with the desired metal in a satisfactory manner. Furthermore, even if this is achievable, the coating will significantly increase the cost of the finished pipe, thereby making it unattractive to an end-user/customer.

Second, in most applications there is generally no reason for internally coating a pipe made of plastics, since such a pipe is already sufficiently impermeable and corrosion resistant for the applications to which such pipes are subjected. In other words, internal metallization of plastic pipes appears, at least at first glance, to be counterintuitive, at least in relation to the vast majority of applications to which plastic pipes have, to date, been used or considered appropriate. The present invention, however, benefit from the use of a pipe made of a plastics material having an internal metallic coating, which has usable characteristics and advantages over the pipes of the prior art.

The pipes can made of a plastics material which are internally, metallically, coated, so as to bring about advantages in relation to the transportation and distribution of compressed natural gas (CNG) at medium or low pressures, i.e. at pressures below 100 bar. Due to the properties of CNG, such applications, until now, have typically been considered "off-limits" to plastic pipes, due to the potential for gas losses through the walls of the pipes - the metallic coating, however, addresses that concern.

The pipes can even be made of a plastics material which are internally, metallically, coated, so as to bring about advantages in relation to the transportation and distribution of domestic natural gas at low pressures, i.e. at pressures usually used in domestic distribution applications, e.g. 95 bar or less, including pressures down to 1 barg (or 1 bar above atmospheric pressure).

Preferably the pipes are made of a plastics material which are internally, metallically, coated, and which are easy to produce, join and inspect.

The various aspects of the present invention may be incorporated into a system for loading and storing CNG onboard a ship and for unloading CNG therefrom, the system comprising:

CNG loading facilities for loading CNG on board of the ship;

CNG storage facilities for storing the loaded CNG onboard the ship at storage pressures and temperatures;

CNG unloading facilities for unloading CNG to a delivery point, the delivery point requiring the unloaded CNG to be at delivery pressures and temperatures generally different from the storage pressures and temperatures,

wherein the CNG unloading facilities comprise:

a CNG heater for heating the to-be-unloaded CNG prior to unloading;

a lamination valve for allowing the to-be-unloaded CNG to expand from the storage pressure to the delivery pressure prior to unloading.

The loading and unloading facilities may be on a platform, on a buoy or on a jetty, or on a connected piece of equipment, either on a ship or in or on the water, e.g. on the seabed, or on a floating (submerged or surface located) vessel. The storage facilities, on the other hand, will typically be on the ship. The various aspects of the present invention may also be used in a method for loading and storing CNG onboard a ship and for unloading CNG therefrom. In a preferred method, the method additionally comprises the sequential steps of:

loading CNG onboard a ship;

storing the loaded CNG onboard the ship for transportation purposes at a range of storage pressures and temperatures; and

unloading the to-be-unloaded CNG from the ship to a delivery point, the delivery pressures and temperatures of the unloaded CNG being a range that is generally different from the range of storage pressures and temperatures, wherein the step of unloading the to-be-unloaded CNG from the ship comprises the steps of:

heating the to-be-unloaded CNG prior to unloading; and

allowing the then heated, to-be-unloaded CNG to expand freely through a lamination valve whereby the to-be-unloaded CNG can be delivered at the delivery point at the delivery pressure and temperature.

The present invention can comprise a hybrid pipe comprising:

an inner metallic layer or sleeve having an inner side which, in use, is in contact with the CNG, and an outer side; and

a composite material over-wrapping layer or sleeve wrapping over the inner metallic sleeve all around the outer side thereof;

wherein the composite over-wrapping sleeve comprises fibres oriented substantially transversally with respect to the pipe's axis.

The pipe may be on the ship, or in or on the loading/offloading equipment, e.g. on a platform, a jetty or a buoy, or in or on the pipework extending between, on or from any one or more of said components of the system.

Preferably the inner metallic layer or sleeve is provided as a liner for the hybrid pipe, the liner having a wall thickness comprised in the range of between 0.5 to 2 mm.

Preferably the inner side of the inner metallic layer or sleeve is corrosion resistant with respect to raw CNG.

The term CNG means compressed natural gas, be it well stream fluids, i.e. gas and liquid hydrocarbons received untreated from the source, or treated compressed natural gas - which will have fewer impurities.

CNG fluids can include various potential component parts in a variable mixture of ratios, some in their gas phase and others in a liquid phase, or a mix of both. Those component parts will typically comprise one or more of the following compounds: C ₂ H ₆ , C ₃ H ₈ , C ₄ H ₁₀ , C ₅ H ₁₂ , C ₆ H ₁₄ , C ₇ H ₁₆ , C ₈ H ₁₈ , C ₉ + hydrocarbons, C0 ₂ and H ₂ S, plus potentially toluene, diesel and octane in a liquid state.

Preferably the inner metallic layer or sleeve is both CNG corrosion resistant and CNG impermeable.

Preferably the composite over-wrapping layer or sleeve is a fibre-wound overwrap.

Preferably the over-wrap comprises a fibre tape wound fully around the circumferential extent of the hybrid pipe.

Preferably the fibre tape is a resin impregnated fibre tape.

Preferably the tape is formed with fibres that are disposed substantially parallel to each other along the tape's longitudinal direction.

Preferably the tape is wound around the pipe in a repeating hoop pattern.

Preferably the composite over-wrapping layer or sleeve comprises a thermosetting resin.

Preferably the over-wrapping layer or sleeve has a thickness comprised in the range of between 5 and 40 mm.

Preferably the internal diameter of the pipe is in the range of between 3 inches (approximately 7.5 cm) and 12 inches (approximately 30 cm).

Preferably the fibres comprise at least one of carbon fibres, glass fibres or KevlarO/aramid fibres.

Preferably the composite over-wrapping layer or sleeve comprises a translucent resin.

Preferably the composite over-wrapping layer or sleeve comprises translucent glass fibres.

The hybrid pipe may comprise multiple overlying over-wrapping layers or sleeves.

Preferably each over-wrapping layer or sleeve comprises a translucent resin. Preferably each over-wrapping layer or sleeve comprises translucent glass fibres. A first composite sleeve may be in contact with the inner metallic sleeve, and a second composite sleeve may be wrapped all around the first composite sleeve. In a preferred arrangement the resin to fibre ratio for the second composite sleeve is lower than the resin to fibre ratio for the first composite sleeve.

An additional over-wrapping sleeve may be wrapped all around the second composite sleeve, and the resin to fibre ratio for this third composite sleeve may be lower than the resin to fibre ratio for the second composite sleeve. Preferably the fibres in one or more of these layers are within 5° of perpendicular to the axis of the pipe, measured circumferentially.

The present invention can also comprise a hybrid pipe comprising:

a first pipe and a second pipe, the first and second pipes having substantially similar internal and external diameters, the first and second pipes being end-to-end welded together so as to form a weld line extending all around the hybrid pipe; and a composite material over-wrapping strip covering the weld line all around the hybrid pipe,

wherein the composite strip comprises fibres oriented substantially transversally with respect to the weld line. This provides strength in the appropriate orientation to resist bursting of the joint.

Preferably the first and second pipes each have a thickness comprised in the range between 0.5 and 2 mm, them together forming a liner for the hybrid pipe.

Preferably the liner is CNG corrosion resistant and CNG impermeable.

Preferably the composite over-wrapping strip comprises a thermosetting resin.

Preferably the strip comprises a translucent resin and/or translucent fibres.

Preferably the strip has a thickness of between 5 and 40 mm.

Preferably the strip comprises intertwined fibres arranged to form a cloth or fabric of fibres.

Preferably the intertwined fibres comprise weft fibres and warp fibres.

Preferably the weft fibres are arranged substantially transversally with respect to the weld line, and the warp fibres are arranged substantially parallel with respect to the weld line.

Preferably the strip comprises a plurality of layers of fibre fabrics.

Preferably the strip is wound around the weld line.

Preferably the strip comprises a tape of fibres wound around the weld line.

Preferably the strip extends either side of the weld line in the direction of the axis of the pipe to cover both the first and second pipes for a length of at least 10% of the average external diameter of the first and second pipes.

Preferably a sleeve of composite material is provided around substantially the whole length of the hybrid pipe, the strip being fully covered by the sleeve of composite material. Preferably the external diameter of the hybrid pipe is substantially constant across the full length of the pipe, including the section thereof where the strip is located.

Preferably the external diameter of the hybrid pipe is enlarged around the section thereof where the strip is located.

Preferably at least some of the fibres are formed as roving fibres.

Preferably the fibres comprise one or more of carbon fibres, glass fibres or KevlarO/aramid fibres.

The present invention also can comprise a piping network comprising a plurality of pipes as described above.

The apparatus can have a hybrid pipe that is preferably arranged such that in use an inner side of an inner metallic layer or sleeve is in contact with the CNG. The pipe further has an outer side and ther pipe is formed by over-wrapping a composite material over the inner metallic sleeve all around the outer side thereof, the composite over-wrap comprising fibres, those fibres being arranged by the wrapping process to be oriented substantially transversally with respect to the pipe's axis.

The present invention also provides a method of inspecting the system's hybrid pipes, the pipes comprising an inner metallic component pipe and an outer composite component pipe over-wrapping the inner pipe and made of at least one translucent material, the translucent material or materials comprising either or both a translucent resin and a plurality of translucent fibres, the method comprising the step of:

visually inspecting the outer composite component pipe to detect defects located at an interface between the metallic component pipe and the outer composite pipe, wherein visually inspecting the outer composite pipe to detect defects comprises identifying a region having at least one non-uniform optical property compared to an adjacent region.

Preferably one of the optical properties is a coefficient of reflection.

Preferably one of the optical properties is a coefficient of refraction.

These hybrid pipes typically provide lighter pipes for CNG operations in CNG pipe networks. This can be both for on-shore or off-shore networks, or networks stretching across both on-shore and off-shore applications. They are particularly beneficial for elements of loading and off-loading equipment for ships, e.g. for loading or offloading buoys, platforms or jetties (whereby less of the equipment's buoyancy is consumed by the weight of the pipes). Indeed, it is anticipated that the pipes of the present invention will be one sixth to one third of the weight of equivalent metal pipes, i.e. pipes that have a comparable fluid flow and fluid pressure capacity.

The weight saving will also allow these composite pipes to be easier to transport and install, while still being manufactured to the current standard sizes.

The lower weight of the pipes might even allow the pipes to be manufactured in larger (particularly longer) sizes, while still being lighter than the equivalent, albeit shorter (or narrower), steel pipes. The present invention might therefore permit fewer joints or flow-lines (and thus again fewer joints) to be necessary within a given pipe network, or a given pipe run.

A further advantage of the present invention is that the pipes will be better thermally insulated compared to the equivalent steel pipes. This is since the composite materials are typically less thermally conductive than the traditional steel of metalic pipes.

The pipes of the present invention can also suffer less from localised weaknesses arising from welded joints.

Another advantage will be that if welding is required, the component to be welded can be a thinner piece of metal, rather than needing to be a weld across the full thickness of the pipe wall. Thinner welds are generally more reliably accurate and complete - thicker welds can more easily suffer from faults or flaws.

An additional advantage of the present invention is that forces at the points at which the pipes are supported externally, e.g. at pipe clamps, or other supports, can be reduced - the lower weight pipes need less securement, and will impart a lower load themselves upon those supports.

An additional advantage is that there will be either no, or a reduced amount of, galvanic coupling of the materials at these clamping points.

The pipes of the present invention, therefore, will be easier to support/clamp into their final positions.

Another advantage of the pipes and piping systems of the present invention is that they may be less prone to the often minimal warning of impending catastrophic failures, compared to the metal pipes of the prior art - metal pipes can often completely fail, i.e. burst, with minimal visual warning, whereas composite structures typically provide visual indicators in the run-up to a failure. This can be by way of showing cracks or generic damages to the fabric and/or the matrix of the structure through a change in the optical properties of the composite resin, aka hazing. Therefore, in certain embodiments of the present invention, it will be possible to perform a visual inspection of the pipes from their outside so as to try to detect possible internal damage to the walls of the pipes.

According to another aspect of the present invention, the system may comprise an internally coated pipe, wherein the pipe is made of a thermoset plastics material, the internal coating being made of a metallic material. For example, the pipe may be on the loading/offloading arm, or in a position connecting various elements of the system. By providing such a pipe, the strength characteristics of a thermoset plastics material (higher than typical thermoplastic plastics materials) can be usefully combined with the impermeability characteristics achievable by use of a metallic coating layer - thermoset plastics are typically less impermeable for a given thickness of material than thermoplastic plastics, and therefore most, if not all, plastic pipes used for gas delivery/distribution applications are made of thermoplastic plastics materials, such as PE and MDPE, so as to avoid undesired gas leakage through the wall of the pipes. Such pipes may be more flexible than composite pipes with a fibre overwrap, although the thermoset plastic may likewise be overwrapped.

Preferably, said thermoset plastics material is one of: epoxy resin, polyester resin and dicyclopentadiene (DCPD) resin. These are all widely used. Further they are all easy and cheap to supply.

In preferred embodiments, said thermoset plastics material is DCPD. That is because DCPD is considered to have one of the highest tensile strengths amongst the above three materials while having their same or similar lightweight properties.

Preferably said metallic material comprises or contains one of: gold, silver, nickel, chrome, palladium, platinum, copper and aluminium, or alloys thereof. All of these metals are known to have characteristics to allow them to be used in deposition applications.

In some embodiments, the thickness, or average thickness, of the coating is less than 0.5 mm. Smaller thicknesses minimise the amount of metal used, which keeps the cost of the materials down.

In preferred embodiments, said internal coating is a film. A film will generally be sufficient to ensure impermeability for the pipe, while minimising the amount of metal needed. The film can be thinner than 1 mm, and preferably thinner than 0.5mm. In some embodiments, the thickness or average thickness of the coating (i.e. of the film), is less than 100 microns. That film can be deposited onto the inside of the plastics pipe. In preferred embodiments, however, the deposited thickness of the metallic coating is sufficient to provide impermeability to the pipe for the target fluid of containment, and at the target range of operating pressures.

In certain low-pressure applications, it is envisaged that an average thickness for the coating layer will be in the order of a few microns, i.e. not more than 10 microns. For such thin coatings, more precious materials can be used, such as gold or silver, without causing excessive or prohibitive costs. This has the advantage of making use of those materials' good impermeability characteristics, or even better impermeability characteristics than materials such as steel, whereby the thin coating thicknesses do not compromise the effectiveness of the film.

In some embodiments, the average external diameter of the pipe is in the range of between 50 and 200 mm. Such diameters provide for many fluid handling situations, and are a preferred range of diameters for pipes used for distributing CNG at pressures lower than 100 bar. Diameters down to 10mm might even be useable. An example diameter might be about 100mm.

Preferably, the thickness of the wall of the pipe is in the range of between 5 and 30 mm. Such thicknesses will provide a pipe with an adequate strength for handling fluids at low pressure. A thickness down to 1 mm might even be possible, and an example thickness might be about 10mm. Thicker wall thicknesses, such as the 30 mm walls, however, would more usually be provided for pipes that handle pressures up to 100 bar, compared to pipes designed to handle pressures of up to 10bar, or 35 bar. The overall outer diameter will also determine the necessary wall thicknesses. The necessary calculations for determining suitable wall thicknesses are well known to structural engineers, based upon hoop-strength requirements.

Preferably, the internal coating is impermeable to the component fluids of CNG, so that the gas can be safely transported. CNG typically comprises any one or more of the following constituents: C ₂ H ₆ , C ₃ H ₈ , C ₄ H ₁₀ , C ₅ H ₁₂ , C ₆ H ₁₄ , C ₇ H ₁₆ , C ₈ H ₁₈ , C ₉ + hydrocarbons, C0 ₂ , H ₂ S, and potentially also toluene, diesel and octane in liquid form.

Preferably, the internal coating is CNG resistant, so that the gas (i.e. the constituents thereof) cannot corrode or otherwise chemically damage the coating and the pipe.

In preferred embodiments the thermoset plastic material is translucent. This can be so that the inner metallic layer can potentially be inspected from outside of the pipe. Preferably, the thermoset plastic material is transparent. This can also help the inspection to be facilitated.

Preferably, the pipe comprises a flange, or some other joining or attachment means (a coupling member), for attachment thereof to another pipe. This is so that pipe junctions and piping networks can be built easily.

In some embodiments, the pipe will be equipped with securing or retention means, so that the pipe can be secured or fixed to another pipe without additional, or separate, coupling means.

The system of the present invention may comprise an internally coated pipe wherein the pipe is made of a thermoset plastics material, and the internal coating is made of a metallic material. The pipe can optionally have any one of the features mentioned above.

The pipe may be produced by providing a pipe made of a thermoset plastics material and depositing a metallic coating onto an internal wall of the pipe.

Preferably the pipe contains CNG at a medium to low pressure (100 bar or less).

The method may comprise the steps of: filling the pipe with an electroless deposition reducing solution and providing an electroless deposition device in contact with the reducing solution. Such a method allows the pipe to be conveniently and cheaply produced.

There might instead be another method, without a solution, involving depositing the metal via a sprayed mixture that contains the metal, the catalyst and air (or a gas), and potentially also various other chemical compounds that are helpful or necessary for the process.

Preferably, the method comprises the step of providing a catalyst to increase the affinity between the metal and the plastics pipe.

Preferably the method comprises the step of cleaning the internal wall of the pipe in preparation for electroless deposition. The cleaning step is likely to increase the effectiveness or longevity of the metal deposition.

It might also be desireable to deposit a less affine metal as second layer over a more affine first layer, i.e. to use a second, low affinity, layer over a first, high affinity layer (whereby the second layer would be less capable of sticking to the internal wall of the pipe than the first layer). This allows that second layer's material nevertheless to be used in the pipe's construction. This would reduce costs if the first layer - the one that sticks to DCPD - is an expensive material, or if it involves an expensive deposition process.

The present invention will now be described, purely by way of example, with reference to the accompanying drawings in which:

Figure 1 is a flow-chart representing an arrangement of loading and storage facilities onboard of a CNG carrier ship;

Figure 2 is a flow-chart representing an arrangement of unloading facilities onboard of a CNG carrier ship;

Figure 3 is a schematic plan view of a CNG carrier ship comprising features from Figures 1 and 2;

Figure 4 is a block logic diagram showing loading and unloading operations comprising features from Figures 1 , 2 and 3;

Figure 5 is a flow-chart representing an arrangement of unloading facilities onboard of a CNG carrier ship;

Figure 6 is a schematic plan view of a CNG carrier ship comprising features from

Figures 1 and 5;

Figure 7 is a block logic diagram showing loading and unloading operations comprising features from Figures 1 , 5 and 6;

Figures 8 to 10 schematically illustrate a CNG carrier ship featuring a plurality of all-steel presure vessels;

Figures 1 1 to 13 schematically illustrate a CNG carrier ship featuring a plurality of composite presure vessels, e.g. type 3 or type 4 - such vessels are likely to have a larger diameter than steel pressure vessels, and they might be longer;

Figures 14 to 17 schematically illustrate a CNG carrier barge featuring a plurality of composite presure vessels, e.g. type 3 or type 4;

Figure 18 is a schematic representation of a pipe in a CNG pipe network formed by welding two pipes, one seamless and one with a welded seam, according to an embodiment of the present invention;

Figure 19 is a schematic cross sectional representation of a welded pipe according to an embodiment of the present invention, with a welding reinforcement and a composite over-wrap, the over-wrap having a constant outer surface profile and a stepped thickness encompassing the welding reinforcement, and;

Figure 20 is a schematic cross sectional representation of a welded pipe according to an embodiment of the present invention, with a welding reinforcement and a composite over-wrap, the over-wrap being moderated to encompass the welding component, thereby maintaining a generally constant thickness;

Figure 21 is a schematic representation of a section of a pipe supported by a clamping arrangement;

Figure 22 is a schematic graphical representation of contact pressure distributions, comparing the values to be found between a support and a) a pipe according to the present invention and b) a metal pipe from the prior art;

Figure 23 is a schematic cross sectional representation of a wall of a pipe according to an embodiment of the present invention showing an internal metallic layer and three composite over-layers, each having different matrix and fibre contents;

Figures 24 to 26 are schematic illustrations to assist in explaining the mechanism of polymer crazing.

Figure 27 is a cross sectional representation of a section of an alternative form of pipe in accordance with the present invention;

Figure 28 is a representation of a method of depositing an internal metallic coating layer on a pipe made of a thermoset plastics material, according to the present invention;

Figure 29 is a cross sectional representation of two joined flanged pipes, each pipe being in accordance with an embodiment of the present invention;

Figure 30 illustrates a possible CNG buoy/platform scenario;

Figure 31 shows an example of a fixed platform with two independent loading/offloading arms;

Figure 32 shows a schematic view of an alternative loading/offloading platform with two arms - this one floating on the water surface and arranged to rise and fall with the tide up a set of legs. The legs fix the platform in the transverse direction;

Figure 33 shows a CALM buoy;

Figure 34 shows a STL buoy;

Figure 35 shows a SLS buoy;

Figure 36 shows a SAL buoy;

Figure 37 shows an IPS OWEC device with a surface buoy;

Figure 38 shows an implementation of three IPS OWEC devices (one shown in full) with a CALM buoy; Figure 39 shows an implementation of two IPS OWEC devices with a buoy and a Gas Dehydration and Compression unit (GDC), connected to a loading/offloading platform;

Figure 40 schematically illustrates a basic scheme of use of a GDC unit;

Figure 41 illustrates an example of a pultrusion technique; and

Figure 42 shows an alternative implementation of two IPS OWEC devices with a buoy and a Gas Dehydration and Compression unit (GDC), this time connected to a FPSO (a Floating Production, Storage and Offloading unit) in the form of a ship.

Referring first of all to Figures 30 to 38, it is to be recalled that CNG loading and offloading procedures and facilities depend on several factors linked to the locations of gas sources and the composition of the gas concerned.

With respect to facilities for connecting to ships (buoys, platform, jetty, etc ..) it is desirable to increase flexibility and minimize infrastructure costs. Typically, the selection of which facility to use is made taking the following criteria into consideration:

· safety;

• reliability and regularity;

• water depth and movement characteristics; and

• ship operation: proximity and maneuvering.

A typical platform comprises an infrastructure for collecting the gas which is connected with the seabed. See, for example, Figure 30, where the pipeline end manifold (PLEM) is connected with the seabed, and a platform is located at the surface of the water. See the left side of the illustration, and Figure 31 . The platform may be connected to the seabed - see Figures 32 and 39, and it may be fixedly mounted or it may be floating.

The right hand side of Figure 30 instead shows a PLEM connected to an onshore treatment plant, e.g. for treating delivered CNG ready for delivery to the final delivery point.

Both the right hand side and the left hand side arrangements in Figure 30 have two buoys. In the right hand side arrangement, however, there is no platform. Further, its second buoy is optionally set up for continuous off-loading, whereas in the left side the second buoy is set up for continuous loading.

Other arrangements are anticipated too, including buoys for offloading and loading. A jetty is another typical solution for connecting to ships (loading or offloading) which finds application when the gas source is onshore. From a treatment plant, where gas is treated and compressed to suitable loading pressure as CNG, a gas pipeline extends to the jetty and is used for loading and offloading operations. A mechanical arm extends from the jetty to a ship, or a buoy can be provided with a pipe extending from the jetty.

Jetties are a relatively well-established solution. However, building a new jetty is expensive and time-intensive. Jetties also require a significant amount of space and have a relatively high environmental impact due to their shore-based, or near shore, location, specifically in protected areas. They are also an inconvenience for marine traffic since they can block the passage along the shoreline.

The present invention provides for improvements to these and other loading and off-loading arrangements.

To improve floating structures, and to enable high pressure operations on such structures and elsewhere, it is disclosed herein to provide the loading arms of the platform/jetty with a hybrid design, for example having piping or structural elements with an inner metal containment liner and over-wrapped composite structural elements. Alternatively, lined pipe arrangements can be provided, whereby the lining rather than the thickness of the pipe provides non-permeability. These approaches both can reduce the weight of the pipework for a given pressure and temperature capability, thus facilitating the reduction of the assembly cost of the structure, e.g. due to easier delivery to the location of the fit-out, and additionally it can reduce the cost of the floating structure used to carry the components to the location or actually in situ - the floating structure need not be so buoyant, and thus it can be smaller, or it can be loaded with additional optional equipment that would otherwise be excluded due to weight concerns, and without adding to the cost of the actual floating structure - there is no need to increase the inherrent buoyancy of the structure.

In the preferred arrangements, the non-flexible portions of the loading arms or pipes are constituted by simple tubular elements, wherein the composite structure may be simply hoop-wrapped. This has the aim of saving weight on the floating structure.

According to the type of composite materials involved the weight saving may be as much as 50% in case of a glass-based composite structure and as much as 65% in case of a carbon-based design. Various types of offloading or loading structure may be provided. We have mentioned platforms and jetties. Buoy systems are also in use. Solutions utilizing buoys can be categorized as follows:

• CALM buoy systems - see, for example, Figure 33;

· STL systems - see, for example, Figure 34;

• SLS systems - see, for example, Figure 35; and

• SAL systems - see, for example, Figure 36.

These have been discussed already in the text above, but in brief a Catenary Anchor Leg Mooring (CALM) buoy is a type of buoy that is particularly suitable for shallow water. The system is based on having the ship moor to a buoy floating on the surface of the water. The main components of the system are: a buoy with an integrated turret, a swivel, piping, utilities, one or more hoses, hawsers for connecting to the ship, a mooring system including chains and anchors connecting to the seabed. The system also comprises a flexible riser connected to the seabed. This type of buoy requires the support of an auxiliary/service vessel for connecting the hawser and piping to the ship. A Submerged Turret Loading System (STL) comprises a connection and disconnection device for rough sea conditions. The system is based on a floating buoy moored to the seabed (the buoy will float in an equilibrium position below the sea surface ready for the connection). When connecting to a ship, the buoy is pulled up and secured to a mating cone inside the ship. The connection allows free rotation of the ship hull around the buoy turret. The system also comprises a flexible riser connected to the seabed, but requires dedicated spaces inside the ship to allow the connection. A Submerged Loading System (SLS) consists of a seabed mounted swivel system connected to a loading/offloading riser and acoustic transponders. The connection of the floating hose can be performed easily without a support vessel. By means of a pick up rope the flexible riser can be lifted and then connected to a corresponding connector on the ship. A Single Anchor Loading (SAL) comprises a mooring and a fluid swivel with a single mooring line, a flexible riser for fluid transfer and a single anchor for anchoring to the seabed. A tanker is connected to the system by pulling the mooring line and the riser together from the seabed and up towards the vessel. Then the mooring line is secured and the riser is connected to the vessel.

In cases where the buoy is anchored to the seabed, the buoy may be surrounded by offshore wave energy converters (OWEC)-buoys. These buoys can be connected to a linear generator, such as for example an IPS OWEC buoy. These are already known from commercial literature.

Such wave energy converters may be cabled to the same subsea connector of the main gas offloading buoy. The accumulated energy can be useful for gas compressors or other loading/offloading equipment. The stored energy, e.g. excess energy, may also be transferred to a ship, for example when the main gas offloading buoy is connected to the ship.

Utilising OWEC wave energy converters, whereas before a high sea state was a scenario to avoid during loading/offloading activities, but by means of this embodiment it is possible to operate even in high seas - the high seascause additional energy to be captures. In fact this embodiment foresees an improved anchor system that allows operating with increased safety and in the meanwhile it is possible to recovery a huge amount of energy during very high sea state.

The present invention therefore achieves or provides:

1 . a buoy system for loading CNG from gas well to CNG ship and offloading gas from CNG ship to gas delivery network with high operating pressure (e.g. 250 bar).

2. A buoy system able to gather and store wave energy to be used during loading/offloading practices.

3. A buoy system able to withstand high or very high sea states.

4. A buoy system where the riser connecting the CNG buoy to the subsea piping manifold is a composite riser.

5. A loading/offloading system by mean of loading/offloading arms having an hybrid metal-composite structure (an hydraulic metal liner and a composite structural over-wrap to reduce weight).

Referring next to Figures 39, 40 and 42, Figures 39 and 42 represent hypothetical applications of a Gas Dehydration and Compression unit that is in this instance a submerged unit located on the seabed. In the drawings, there is shown a gas well 21 1 that is located on the seabed 209. A pipe 213 extends from that gas well to a Gas Dehydration and Compression unit 212. Both end units being fixed, that pipe may be made from a hybrid pipe such as any of those discussed herein, although it is typically will be a low to medium pressure pipe, dependnet upon the outflow pressure from the gas well, and thus might economically be a metal lined pipe. A metal pipe would also provide the desired function., and as such it could be a conventonal pipe instead, rather than an inventive hybrid pipe.

From a gas outlet 227 of the GDC, a riser 214 is provided. This riser is a pipe for delivering gas from the GDC to a ship. It is preferably a hybrid pipe along at least a part of its length since its weight is beneficially minimised - it attaches at its other end to a gas loading buoy 215, and thus the buoyancy of that buoy needs not to be compromised by the weight of the riser 214.

The operation of the GDC is described later with reference to Figure 40, but in

Figures 39 and 42 it can be seen also to have a liquid outlet 226 and it is also connected to, in this embodiment, a pair of Offshore Wave Energy Converter units

(OWECs 216), each having a floating buoy at its top. These OWECs provide power to the GDC by converting wave energy into power. For that connection, power cables 217 are provided. A third power cable 217 also extends alongside a discharge pipe 218 extending from the liquid outlet 226.

The discharge pipe 218 is provided for discharging liquids such as hydrates from the CNG.

Finally, Figures 39 and 42 also illustrate a pair of anchor wires 219, although more than two such wires are likely to be provided. They ensure that the buoy is relatively fixed in its location in the water, rather than it suffering from significant drift as a result of the water movements. Preferably there are at least three such anchor wires 219.

The difference between Figures 39 and 42, however, rest in the destination of the discharge pipe 218 and the third power cable 217. In Figure 39, these extend along and up to a platform 220, which platform provides further loading arms for ships. The power for that platform is provided again by the OWECs, although that could be ancillary power if the platform has its own generators, as it is likely to have. The platform, however, is fixed on legs in a location above the high tide, and high seas. The arms 222, however can be raised and lowered as needed for conencting to ships moored close to the platform 220. In Figure 42, on the otherhand, the discharge pipe 218 and the third power cable 217 extend to a FPSO ship 224. Since this is a floating structure, it is preferred that at least part of the discharge pipe 218 is a hybrid pipe since its weight is beneficially minimised - it attaches at its other end to the ship and thus the buoyancy of that ship needs not to be compromised by the weight of the pipe 218. Referring next to Figure 40, the basic operational scheme of the GDC unit is shown. As can be seen it comprises the pipe 213 from the gas well 21 1 . That pipe feeds raw gas to an inlet cooler 231 . This lowers the temperature of the gas preferably without dropping the pressure of the gas. That cooled gas is then passed through a gas-liquid separator 232 for separating liquid fractions from the gas fraction, such as hydrates or water, which may condense as the fluid cools. The liquids are then pumped away through the liquid outlet 226 using a pump 233, e.g. to the platform or ship 220, 224, for further processing. The pump can be driven by one or more OWEC.

The gas fraction is instead delivered to a compressor 234 for taking the pressure up to the desired CNG pressure, e.g. 250bar or more. This may be done in stages due to the heat formation. Upon compressing the gas, the compressed gas is then cooled using an outlet cooler 235. If the compression is in stages, the cooling may likewise be in stages.

The cooled, compressed CNG is then delivered through the liquid outlet 227 for delivery up the riser 217 to the buoy, wherefrom it can be delivered to a ship.

Referring next to Figures 1 to 17, systems typically on a ship during loading (or offloading), using the various forms of buoy, jetty or platform described above, are disclosed.

In Figures 1 , 2 and 5, the following line styles are used:

· solid lines to represent "process lines", i.e. pipelines or pipe networks used for streaming CNG at predetermined pressure and temperature conditions;

• dashed lines to represent "electric signals", i.e. cabling or cable networks used for carrying electric actuation signals;

· dashed lines to represent, in a mechanical context, "flexible mechanical connections", such as flexible pipelines or pipes;

• long-dash/short-dash lines to represent "facilities located onboard of a CNG carrier ship";

• solid lines with "L" symbols to represent "hydraulic signal lines", i.e. cables carrying actuation signals in the form of liquid pressure;

• solid lines with "II" symbols to represent "pneumatic signal lines", i.e. cables carrying actuation signals in the form of air pressure; • solid or dashed lines with "~" symbols to represent "omitted or interrupted lines", which substitute redundant technical information for representation purposes;

• solid lines with "=" symbols to represent "pipeline end plates" or "pipeline flanged terminations";

• solid lines with "N" symbols to represent "connections between distinct pipeline sections", for example sections belonging to different stream numbers (see below for definition of stream numbers or stream sections);

• solid lines with transversal "I" symbols to represent "pipeline joints" between different sections of pipelines, or between pipelines and other facilities or machinery such as compressors, heat exchangers, pressure vessel units etc.; and

• lines ending with an arrow to represent "CNG flow directions".

In Figures 4 and 7, the following line styles are used:

• thin solid lines to represent flow lines operative during both loading and unloading phase;

• thick solid lines to represent flow lines operative only during spontaneous delivery of CNG during the unloading phase (see below for meaning of spontaneous delivery); and

• thick dashed lines to represent flow lines operative only during delivery with compression during the unloading phase.

In the Figures and in the description, the following abbreviations and/or reference symbols are used:

• barg = "bar gauge", an unit denoting pressure relatively to atmospheric value. It is given by absolute pressure minus atmospheric pressure (nominally taken to be 1 bar)

• FPSO = "Floating Production, Storage and Offloading Unit"

• SDV = "Shut Down and Control Generic Valve System"

• PLEM = "System for Measuring Gas Properties"

• STLS = "Submerged Turret Loading System"

• C = "Failure-Close Valve"

• O = "Failure-Open Valve"

• BDV = "Blow-Down Valve"

• BD = "Blow-Down Piping System" • UN = "Inert Gas Supply System" (usually, the inert gas is nitrogen)

• FO = "Calibrated Orifice"

• PSV = "Pressure Safety Valve"

• CH = "Chemical Injection System" (usually, the chemical is methanol)

• UV = "Blockage Valve"

• DR = "Drainage Piping System"

• FG = "Fuel Gas Supply System" or "Fuel Gas"

• HW = "Hot Water Injection System"

• SW = "Sea Water Injection System"

• TV = "Temperature Controlled Valve"

• FV = "Flow Controlled Valve"; in one instance this is also the main expansion valve, or main lamination valve, i.e. a valve separating an upstream flow of CNG at higher pressures (e.g. 230 barg) and a downstream flow of CNG at lower pressures (e.g. 210 barg)

• FC = "Flow Control Unit"

• PC = "Pressure Control Unit"

• HIPPS = "High Integrity Pipeline Protection System"

• TC = "Temperature Control Unit"

• LV = "Level Controlled Valve"

• LC = "Level Control Unit or System"

• Arabic numerals inside a diamond symbol denote the "Stream Number" or "Stream Section". The stream number and the stream section identify a path or route of CNG wherein the pressure and temperature conditions of the CNG are generally unchanged.

• I = "Intelligent Controller"

• UNIT 120 = "Chemical Injection Module"

• UNIT 170 = "Gas Sealine Module (also referred to as "Gas Loading and Unloading Facility") - this unit is located in the ship's hold, and provides the input/output interface of the ship for loading and unloading of CNG

• UNIT 230 = "Flare, Vent and Blow-Down System"

• UNIT 300 = "Gas Separation and Heating Unit"

• UNIT 360 = "Gas Compression Unit for Scavenging". In this application Energy Scavenging refers to the recovery of CNG from the pressure vessels that otherwise would not be recovered and delivered. • UNIT 361 = "Compressed Gas Storage Facilities" (also located in the ship's hold)

• UNIT 410 = "Hot Water Facility"

• UNIT 420 = "Fuel Gas Supply Unit"

· UNIT 430 = "Diesel Fuel Unit"

• UNIT 460 = "Compressed Air Facility"

• UNIT 470 = "Main Electric Power Generator"

• UNIT 480 = "Emergency Electric Power Generator"

• UNIT 550 = "Closed Drains"

· UNIT 600 = "Inert Gas (Nitrogen) Supply Unit"

• AA = "Air"

• DC = "Closed Drain System"

Figures 1 to 4 relate to a first case study involving operations of loading, storage, transportation and unloading of CNG respectively on and from CNG carrier ships related to an offshore natural gas production site in Northern Europe. The delivery destination in this first case study is also in Northern Europe, and is referred to for simplicity as location "K". The K delivery point accepts CNG at temperatures around 10 degrees C and pressures in the order of 1 10 -120 bar.

Figures 1 , 5, 6 and 7 relate to a second case study also involving operations of loading, storage, transportation and unloading of CNG respectively on and from CNG carrier ships also related to a natural gas production site in Northern Europe. The delivery destination in this second case study is different from the one in the first case study, although it too is in Northern Europe. This second delivery destination is referred to as location "B" for simplicity. The B delivery point accepts CNG at temperatures around 20 degrees C and pressures in the order of 1 10 -120 bar. B accepts, therefore, slightly hotter CNG than K. K and B have been taken here as examples, but different delivery locations may exist, and the pressure and temperature requirements at different delivery locations may change considerably, e.g. depending upon local custom or energy provider requirements.

Figure 1 , which is a flow chart representing the CNG loading phase, is representative of both the first and second case studies. In other words, the CNG loading phase is practically the same for the K and B cases. Figure 1 uses a submerged turret loading system, although other forms of buoy, platform or jetty could also apply. Figures 3 and 6 represent respectively ship facility lay outs for the K and B cases. There are differences between Figures 3 and 6. However, these differences are minimal and they will be only briefly discussed below.

Figures 2, 4, 5 and 7 illustrate for respectively the K and B cases, how the CNG is handled on the ships in preparation for, and during, offloading of the CNG at the K and B delivery points. There is a difference between the CNG unloading phases in the K and B cases - this difference will be described in detail below. The difference, which is imposed by the different CNG delivery conditions at the K and B delivery points, and which is basically one missing cooler from Figures 5 and 7 compared to Figures 2 and 4, is clearly visible from a comparison of those Figures.

Natural gas might be extracted from underwater wells and, from those wells, it is first stored in a Floating Production Storage and Offloading unit FPSO (see Figure 1 ). Here it is called the Goliat FTSO.

At the FPSO, the natural gas is treated and stored at the nominal transportation pressure, for example 230 barg (high pressure), and then loaded and stored into CNG carrier containment system (pressure vessels) at the same high pressure value. By contrast, the pressure of residual CNG contained in pressure vessels on CNG carrier ships about to load CNG from the FPSO is around 30 barg (low pressure).

Before being loaded onto the CNG carrier ship, the physical and chemical properties of the natural gas are measured at a PLEM station (see Figure 1 ). The PLEM station has a system of valves SDV for regulating the flow of CNG therethrough. The valve system SDV comprises a fail-close valve C, and is controlled by a controller I which communicates hydraulically with valve C.

CNG stream 1 , for both the K and B cases, is at approximately 230 barg and at a temperature value depending on gas treatment present on FPSO. For example, it may be 15°C. As explained above, the CNG is delivered to the ships already pre- compressed and pre-treated. Pre-compression and pre-treatment take place on the FPSO.

According to Figure 1 , via the PLEM station, the CNG is delivered to a submerged turret loading system STLS (the system is hosted on a buoyant structure) by means of a flexible mechanical connection such as a flexible pipe. The submerged turret loading system STLS operates as an interface unit for the CNG carrier ship. The CNG is loaded onto the ship from the STLS. A mains shutter valve system SDV comprising a fail-close valve C is provided on the ship, downstream of the entry point of the CNG in the ship, to block ingress of CNG in the ship, if necessary, for safety reasons. CNG stream 2 in Figure 1 is about at the same conditions as the gas of stream 1 , e.g. also at around 230 barg and 15 degrees C - this is due to the fact that the CNG has not yet undergone any thermodynamic transformation on the ship.

On the ships, a storage system is provided for storing the loaded CNG. The storage system can consist of pressure vessels grouped in hold spaces (modules) for safety reasons. For example, the CNG carrier ships might have 8 storage modules, and each module might have 70 pressure vessels (PVs). That might in particular be suitable for steel PVs. With composite PVs, there might be fewer, since they might be larger. For example there might be 6 modules and 50 PVs for each module.

Each module can be divided into sealed compartments, and each compartment can comprises 70 steel PVs or 50 composite PVs, or other numbers, e.g. 60 and 10 - the number of modules, compartments in each module and PVs in each compartment can vary, as it will be recognised by the skilled person.

9 PVs per compartment are also possible, and these can be grouped three by three.

The storage system of PVs is supplied by a loading distribution network of pipes 20, as shown in Figure 1. The loading distribution network of pipes 20 is drawn vertically in Figure 1 , and it is delimited by end flanged termination 21 , 22. The loading distribution network is connected to a safety blow-down system 23 which comprises a blow down valve BDV with relative, safety fail-open valve O. The blow down valve BDV is connected to a blow down pipe network BD. The blow-down pipe network is eventually connected to a flare on the ship. The blow down system is used in emergencies, e.g. if pressures above any allowed limits are reached in CNG stream section 2 for any reasons.

Individual module supply pipes 31 , 32 connect the distribution piping network 20 with each of the modules 41 , 42. Other modules are present in the ship, as discussed above, but in Figure 1 for representation purposes only two modules 41 , 42 are shown.

Each supply pipe 31 , 32 has its own shut-down and control valve system SDV, and each valve system SDV comprises its fail-close valve C. In this manner, each module 41 , 42 can be isolated upstream from the remainder of the system when necessary. Pressure vessels for the transport of compressed fluids presently constitute four regulatory agency approved classes or types, all of which are cylindrical with one or two domed ends:

Type I. Consists of an all metal, usually aluminum or steel, construct. This type of vessel is inexpensive but is very heavy in relation to the other classes of vessels. The entire vessel is of sufficient strength to withstand the intended pressure exerted on the vessel by a contained compressed fluid and therefore does not require any manner of strength-enhancing over-wrap, including the dry filamentous over-wrap of this invention. Type I pressure vessels currently comprise a large portion of the containers used to ship compressed fluids by sea, their use in marine transport incurs very tight economic constraints.

Type II. Consists of a thinner metal cylindrical center section with standard thickness metal end domes such that only the cylindrical portion need be reinforced, currently with a composite over-wrap. The composite wrap generally constitutes glass or carbon filament impregnated with a polymer matrix. The composite is usually "hoop wrapped" around the middle of the vessel. The domes at one or both ends of the vessel are of sufficient strength to withstand the pressures developed in the vessel under normal use and are not composite wrapped. In type II pressure vessels, the metal liner carries about 50% of the stress and the composite carries about 50% of the stress resulting from the internal pressure of the contained compressed fluid. Type II vessels are lighter than type I vessels but are more expensive.

Type III. Consists of a thin metal liner that comprises the entire structure, that is, the cylindrical center section and the end dome(s). Thus, the liner is currently reinforced with a filamentous composite wrap around entire vessel. The stress in Type III vessels is shifted virtually entirely to the filamentous material of the composite wrap; the liner need only withstand a small portion of the stress. Type III vessels are much lighter than type I or II vessels but are substantially more expensive.

Type IV. Consists of a polymeric, essentially gas-tight liner that comprises both the cylindrical center section and the dome(s), all of which is currently fully wrapped with a filamentous composite. The composite wrap provides the entire strength of the vessel. Type IV vessels are by far the lightest of the four approved classes of pressure vessels but are also the most expensive.

As noted above, Type II, III and IV pressure vessel currently require a composite over-wrap over a vessel liner to give them the necessary strength to withstand the intended pressure exerted by a compressed fluid contained in the vessel. It is known, however, that the polymeric matrix of the composite wrap adds little or no strength to the overwrap. Thus, this invention also can be used with novel winding arrangements using a dry filamentous material that is disposed over a pressure vessel liner in a dry state and that is remains in essentially a dry state (i.e. not bonded throughout with an impregnation of resin) for the life-time of the pressure vessel.

"Essentially" in a dry state takes into consideration that, in use, particularly for marine transport of compressed fluids, the filamentous material may inadvertently become dampened by environmental moisture and the like. That is, the dry filamentous material is intended to be disposed over the vessel dry and to be dry when the vessel is put in use. Essentially dry in this context therefore does not exclude situations where the filaments/fibres are wetted by water.

Considering now individually the modules 41 , 42, each module is connected to an inert gas system UN 51 , 52 which can supply the module with an inert gas (e.g. nitrogen). The inert gas systems are controlled by respective automatic control valves 57, 58 which can be activated as a function of the value of pressures measured in the modules. If the pressure in any of the compartments of the modules increases, this could mean that CNG is leaking from the PVs in the compartment. The inert gas systems UN 51 , 52 allow an oxygen-scarce atmosphere to be maintained in the compartments, in order to prevent any potential combustion. In other words, the inert gas systems UN 51 , 52 serve to "control" the atmosphere in the modules.

When CNG is present in any of the compartments in a measured quantity above a predetermined value, e.g. exceeding a given number of parts per million, the corresponding automatic control valve 57, 58 opens and allows inert gas UN to flow through the inert gas system 51 , 52 and into the module and compartment.

For safety reasons, each inert system UN 51 , 52 is equipped with a safety blow- down system so as to allow any excess inert gas to be ejected from the inert gas systems when necessary.

Each module 41 , 42 is air sealed in respect of the outer environment. The internal atmosphere in each module is controlled by the possibility of admitting an inert gas into the module, i.e. a gas not capable of sustaining a combustion reaction with any leaked CNG, if the CNG and the inert gas get in contact with each other. Each module has multiple PVs connected by a common manifold 67, 68. For simplicity, Figure 1 only shows three PVs for the upper module 41 and three PVs for the lower module 42.

CNG delivery pipes 61 , 62 are provided separately from the CNG supply pipes 31 , 32 for each module to transfer the stored CNG to the CNG unloading facilities when required.

The CNG delivery pipes 67, 68 are each equipped with a respective pressure safety system 69, 70. Each pressure safety system comprises a pressure safety valve PSV connected to a blow-down pipe network BD. The PSVs are opened when the pressure safety systems sense that the pressure inside the modules is increasing due to leakage of CNG from the pressure vessels. The blow-down pipes BD are connected to the vent system of the ship, as discussed above.

The vent (flare) system can be a cold vent system, i.e. it might not involve a real flame. Instead, this is just a system for releasing CNG into the external environment at a relatively remote location in the air above the ship itself.

For each module, downstream of the pressure safety system and valve PSV, a depressurisation system 72, 73 is located. Like the pressure safety system, the depressurisation system is connected to the module's CNG delivery pipe 61 , 62. Automatic depressurisation valves are in the depressurisation systems 72, 73. These are essentially the same as safety blow-down system 23.

It should be noted that these safety systems 23, 72, 73 also comprise a calibrated orifice FO for regulating the flow rate of dismissed CNG. This is because current norms prohibit the dismissal of uncontrolled quantities of CNG as well as to limit the velocity into the pipes.

Methanol injection by means of methanol injection systems 75, 76 is carried out for each module on the module's CNG delivery pipe 61 , 62, just before shut down and control valves SDV 77, 78. These valves, together with corresponding valves located on the CNG supply pipes 31 , 32 for each of the modules, serve to isolate the modules from CNG flow. Methanol injection is provided so that hydrates formation during unloading can be avoided or minimised. Methanol is known to be a good thermodynamic inhibitor against hydrates formation.

The CNG delivery pipes coming from the various modules and compartments are then connected to an unloading distribution network of pipes 85. Just like the loading distribution network of pipes 20, the unloading distribution network of pipes 85 is connected to a blow-down system 86 comprising as usual a blow-down valve, and to a blow-down pipe system BD, via a calibrated orifice FO, as shown in Figure 1.

The unloading distribution network of pipes allows CNG to be conveyed to the CNG unloading facilities of the ship, for which see Figure 2.

CNG is therefore loaded onto the ship from the FPSO, and stored at a predetermined temperature and pressure in the PVs on the ship.

Figure 2 is a process flow diagram illustrating the flow of CNG during unloading operations at the K delivery point. There are three possible paths or routes for CNG to be unloaded from the ship. These three possible paths are referred to as: a) "spontaneous delivery" path; b) "spontaneous delivery with compression of the CNG transition phase" path; and c) "delivery with compression" path.

During spontaneous delivery, the nominal starting pressure in the PVs is 230 barg. The PVs' pressure tends to decrease as CNG is downloaded from the ship, and - with it - the speed of delivery of CNG decreases. Spontaneous delivery is allowed down to nominal pressures in the PVs well below the original 230 barg, down to pressures just above the delivery pressure (e.g. just above 1 10 -120 barg). The decision whether to allow or not spontaneous delivery of CNG depends on whether it is considered that spontaneous delivery is still able to guarantee download of CNG quickly enough to be economical over the other two possible methods of delivery.

In the second regime (spontaneous delivery with compression of the transition phase), CNG is allowed to be spontaneously delivered via the same route as for case a) (spontaneous delivery). However, since the nominal starting pressure in the PVs is now approximately 126 barg, i.e. very close to the nominal pressure of the delivery point (approximately, between 1 10 - 120 barg), the CNG would be delivered at a temperature well below the required temperature of the K delivery point, which is around 10 degrees C. This would be a natural consequence of the free expansion of the CNG starting from 126 barg - at this pressure the CNG is already colder compared to the temperature of the gas at 230 barg.

Temperature compensation of CNG needs to be provided in the second regime. Furthermore, as the pressure of the CNG in the PVs approaches the equalisation point in respect of the pressure of the delivery point as CNG is still being spontaneously downloaded from the ship, speed of download also gradually decreases. This can lead to unacceptably slow delivery speed. To compensate for this effect, the so-called "transition phase" (i.e. CNG stored in the PVs at a pressure substantially equal to, or slightly below, the pressure of the delivery point) is forced through a compressor. The pressure gradient imposed by the compressor on the CNG transition phase is relatively low, and just sufficient to provide quick and economical delivery of CNG stored in the pressure vessels at pressures equal to or just below the pressure of the delivery point.

In the third regime (delivery of CNG with compression), the pressure of the remaining CNG in the PVs is substantially lower than the pressure required at the delivery point. Therefore, delivery without compression of the residual CNG would not be possible. In the third regime, therefore, CNG is unloaded from the ship by means of a compressor. CNG can be successfully and conveniently downloaded until the residual pressure of the stored CNG is around 30 barg. To download further CNG would not be economical, as the energy required to compress the residual CNG from pressures below 30 barg to approximately at least 1 10 - 120 barg would be excessive. This would go against the overarching objective of maximising the loading/unloading efficiency of the ship.

With reference to Figure 2 (i.e. with reference to the K delivery point), the three possible paths or regimes are, in order, described below in additional detail:

a) Spontaneous Delivery

The spontaneous delivery path of the CNG during unloading is identified by stream numbers 2, 3, 8 and 9. The CNG enters in the downloading section of the ship from the top-left of Figure 2. Lower blockage valve UV 101 is closed. Upper blockage valve UV 102 is instead open. CNG is thus admitted in the unloading section of the ship just before hot water heat exchanger 103, without having prior undergone any thermodynamic transformations.

The pressure and temperature of the CNG at stream number/section 2 are respectively 230 barg and 15 degrees C.

If the CNG was now allowed to expand (i.e. to laminate) freely, its temperature would decrease. This would take the CNG's temperature outside the temperature required at the K delivery point.

Hot water heat exchanger 103 compensates the temperature decrease in the CNG due to free lamination. The hot water heat exchanger, in the assumption that the CNG is at 230 barg and 15 degrees C in input to the heat exchanger, provides a temperature increase to the CNG in the order of around 15 degrees C. The pressure and temperature of the CNG at stream number 3 are therefore respectively around 230 barg and 30 degrees C. It should be noted that stream number/section 4 is not part of this regime - stream section 4 is only accessed when the CNG is required to go through a compression stage.

Safety blockage valve UV 104 is provided on stream section 2 just before the heat exchanger. A further safety blockage valve UV 105 is located on stream section 3 just before the main lamination valve or main expansion valve FV 1 10.

The pressure downstream of the main lamination valve 1 10 is essentially the pressure imposed by the delivery location (taking in consideration also the pressure drop), in this case between 1 10 - 120 barg. The pressure upstream of the main lamination valve is essentially the pressure of the CNG as stored in the PVs.

Controller I 1 15 is responsible for regulating the opening of the main lamination valve FV 1 10. Values of flow and pressure are fed to the controller I, as shown in Figure 2, by flow control unit FC 1 16 and pressure control unit PC 1 17.

Based on the actual pressure gradient between stream sections 8 (downstream of the expansion valve) and 3 (upstream of the expansion valve), the controller 1 1 15 controls the degree of opening of the main expansion valve 1 10. Controller I thus operates in such a way that it ensures that the pressure of the delivered CNG is acceptable, i.e. within the required range.

Temperature control unit TC 120a is located downstream of the pressure and flow control units 1 16, 1 17, along stream section 8. The temperature control unit TC 120a feeds back information on the temperature of the CNG after lamination has taken place to a second controller I 130 which controls the supply of hot water to the hot water heat exchanger 103.

If the delivered gas is too "cold", the hot water heat exchanger 103 can provide the required temperature increase.

Since stream sections 8 and 9 are common to the three regimes, they will be described only once below, after regimes b) and c) have also been described in more detail.

b) Spontaneous Delivery with Compression of the CNG Transition Phase

The pressure in the PVs decreases as CNG is spontaneously delivered to the K delivery point at the required pressure and temperature. Spontaneous delivery is used across a rather broad range of storage pressures, for example between 130 - 230 barg. It will be appreciated that the range of pressures for pure spontaneous delivery can be determined according to specific design and/or application requirements. As the pressure of incoming CNG from the CNG storage facilities of the ship decreases, the temperature of the CNG decreases. Accordingly, the hot water heat exchanger 103 provides additional heat to the circulating CNG, in order to meet the delivery temperature requirement. At a nominal pressure of 127.5 barg, the temperature gradient in the CNG across the hot water heat exchanger is around 20 degrees C. The temperature of the CNG at input to the hot water heat exchanger 103 is approximately -5 degrees C (worst scenario). The temperature of the CNG at output from the hot water heat exchanger 103 is approximately 15 degrees C.

If the speed of transfer of CNG from the PVs to the delivery point is considered to be "too slow" and therefore not efficient, the CNG can be accelerated via compressor CP. Therefore, the CNG to exit from the hot water heat exchanger 103 can be diverted via stream section 4, through compressor inlet knock out drum 140, and finally into compressor CP 150.

The knock out drum 140 is provided simply to separate any liquid phase from the gas (water and/or other hydrated elements), so that only gas enters the compressor CP 150 (it could be damaging for the compressor CP 150 if any liquids were introduced therein).

The knock out drum 140 is connected to a liquid drainage pipe system DR, which is of the closed-drain type. Closed-drain type systems do not allow the drained liquid to be dispersed in the outer environment, such as in the sea. Instead, drained liquids are collected on the ship and delivered at the delivery or loading points for disposal.

A level valve LV 141 and a level control unit LC 142 together control the operation of the drainage of liquid into the drainage pipe system DR. The level control unit LC 142 senses the level of the accumulated liquid in the knock out drum 140.

After passing through the knock out drum 140 or alternative liquid separator,

CNG is admitted in the compressor CP 150, which is driven in a conventional manner by a gas turbine TB. In the example of Figure 2, the gas turbine TB 160 is supplied with CNG fuel gas FG directly obtained from the pressure vessels (stream 7).

The pressure of the CNG at the exit of the compressor CP 150 is sensed by a further pressure control unit PC 151. Pressure control unit PC 151 feeds that information to a further controller unit I 152. Controller unit I 152 also receives information from a further flow control unit FC 153, which monitors the flow rate of CNG from the knock out drum 140 to the compressor CP 150. Controller I 152 then determines whether additional CNG should be drawn from stream section 6 (via a further flow valve FV 154), fed through the knock out drum 140 and then re-injected in the compressor CP 150. In other words, controller I 152 is programmed to be able to generate a feed-back loop of CNG to the compressor CP 150.

Whether the feed-back capability is used or not, is determined by the controller I 152 according to the parameters measured by the pressure control unit PC 151 and the flow control unit FC 153.

Returning now to stream section 5, i.e. the section of pipeline where CNG outputted from the compressor CP 150 flows, a shut down and control valve system SDV 155 comprising a fail-close valve is provided downstream of the point where pressure control unit PC 151 reads the pressure of the CNG out of the compressor CP 150.

Proceeding along the path of the CNG, we come to stream section 6, which is characterised by the presence of a compressed CNG heat exchanger 170a. In the case of transition CNG (or transition phase CNG - i.e. CNG at pressures substantially equal to the delivery pressure), minimal or no heat is exchanged at this heat exchanger 170a. This is because the temperature of the CNG has already been brought to the appropriate level by the hot water heat exchanger 103. It should be remembered that the compressor 150 is responsible for heating the CNG even further. CNG heat exchanger 170a is also referred to as first stage compressor after cooler. This is because its function is to cool the to-be-unloaded CNG if necessary.

A further sea water heat exchanger 180 is then provided along stream section 6, after the first stage compressor after cooler 170a. This latter heat exchanger, also known as gas export cooler 180, allows the CNG to be cooled to an appropriate temperature just prior to delivery. Sea water SW is drawn directly from the sea as a coolant liquid and re-circulated in the sea after use.

Operation of the sea water cooler 180 is controlled by temperature control unit TC 190 and temperature control valve TV 191 as shown in Figure 2, bottom left of diagram.

A blockage valve UV 192 is also provided on stream section 6 downstream of the sea water cooler 180. In this second regime, "spontaneous" and "transition phase" CNG (i.e. CNG stored on the ship at pressures close or equal to the delivery pressure) are delivered at the required pressure and temperature at the K delivery point.

c) Delivery with Compression

Stage b) above allows delivery of stored CNG having pressures relatively close or equal to the delivery pressure. As we have seen, the CNG is allowed through a relatively complex system involving heat exchangers, coolers and compressors to achieve the required delivery characteristics.

The present stage deals with delivery of CNG stored on the ship at pressures substantially below the delivery pressure, e.g. 50 barg. At 50 barg, a PVs is relatively empty.

Stage c) implements essentially a scavenging process in respect of this remaining CNG. The minimum pressure of stored CNG that can be conveniently downloaded from the ship is around 30 barg. It is not convenient to empty completely the pressure vessels. Residual CNG is carried on the ship all the way back to the CNG production and collection point, or used in the ship as fuel.

In the present regime, CNG is admitted into the diagram of Figure 2 from the top left corner as usual. However, upper blockage valve UV 102 is now closed and lower blockage valve 101 is open, so that stream section 1 is now used.

Stream section 1 is characterised by the presence of the CNG heat exchanger

170a. This exchanger has been described in more detail above. This means that low pressure ("cold") CNG is initially heated up using compression residual heat. This preheating step is now necessary in view of the very low pressures and temperatures of the CNG inputted to the downloading facilities. The compressor CP 150 is now required to compress the CNG to pressures (and, therefore, temperatures) suitable to ensure correct functioning of the pre-heater 170a.

After the pre-heating step, the CNG is then routed, in order, through stream sections 2, 4, 5 and 6 exactly as for regime b) above. The pressure gradient established by compressor CP 150 will be, however, greater than in the previous regime, where part of the motive force of the CNG was already stored in the CNG in arrival from the loading facilities (higher pressures). Now, the incoming CNG is at much lower pressures.

For a detailed description of CNG streams 2, 4, 5 and 6 see regime b) above. It should be noted that the feedback loop established by the controller I 152 in conjunction with pressure control unit PC 151 , flow control unit FC 153 and flow valve FV 154 operating between stream sections 6 and 4 will be useful in successfully managing transition regimes between delivery according to regimes b) and c). When the delivery method is switched from b) to c), at early stages the CNG may not yet be ready for delivery, because its pressure and temperature are not yet within the delivery range. If so, the CNG can be re-injected in the compressor CP 150 until satisfactory pressures and temperatures at the output thereof are measured.

CNG coming simultaneously via one or more of the above described delivery regimes is then collected at stream section 7 at substantially the delivery pressure and temperature. A High Integrity Pipeline Protection System HIPPS 199 is provided along stream section 7. The HIPPS 199 comprises a system of close-fail valves C. A shut down and control valve system SDV 198 is also provided downstream of the HIPPS 199. The function of the HIPPS is that of protecting the delivery PLEM system 200 from possible overpressures. PLEMs can be relatively delicate, as they are designed accurately to measure physical and chemical quantities of the delivered CNG.

It is then downstream of "protected" stream section 8 that the CNG leaves the ship via stream section 9. Stream section 9 is implemented by means of a flexible mechanical connection 201 . The delivery PLEM system can be provided on a floating structure. From the delivery PLEM system 200, the CNG is routed to onshore facilities.

In the above-described examples, the compressor CP is a 12 MW unit compressor.

In the loading phase, as said above, CNG is admitted on the ship at about 230 barg and 15 degrees C.

In the spontaneous delivery regime, the CNG entering the CNG unloading facilities is first heated by hot water heat exchanger 103 to about 30 degrees C as an example. After lamination, the gas is delivered for example at about 128 barg and 13 degrees C.

In the spontaneous delivery regime with compression of the transition phase of the CNG, the CNG entering the CNG unloading facilities is, in an example, at about 127 barg and -5 degrees C. The CNG is then pre-heated in pre-heater 103, to about 14 degrees. No further significant thermodynamic events are undergone by the CNG before delivery. The latter conditions are therefore the conditions approximately at which the CNG is delivered.

In the delivery with compression regime, the CNG, in one example, enters the CNG unloading facilities at about 31 barg and -57 degrees C. After pre-heating in the first stage compression after cooler 170a, or after pre-heating in that cooler plus further heating in the hot water heat exchanger 103, the CNG's temperature is about 40 degrees C.

After compression, the pressure of the CNG is about 127 barg and the temperature about 162 degrees C.

After heat has been transferred by the CNG to fresh oncoming CNG at the first stage compressor after cooler, the temperature of the CNG decreases, in the example, to about 36 degrees C.

After the further cooling stage at the gas export cooler, the temperature falls to about 14 degrees C. The CNG is therefore delivered at around 127 barg and 14 degrees C.

Figure 3 shows an example of a layout of CNG management facilities onboard of a ship. Gas compression unit 360 is located on the aft of the ship, on the upper deck. The gas compression unit 360 is also commonly referred to as the "scavenging unit". This is because its function is the recovery of CNG stored in the ship, which would not otherwise be possible to download. In Figure 3, gas compression unit 360 can be seen to comprise three scavenging compressor trains 362, each including a gas turbine and a centrifugal gas compressor. Respective gas turbine oil coolers 363 are also provided adjacent each of the scavenging compressor trains 362. A gas metering module 365 is also part of the gas compression unit 360.

As explained above in connection with Figure 2, the gas metering module comprises a pressure control unit PC and a flow control unit FC. A controller I is also provided in connection with the pressure and flow control units so that CNG can be fed back to the compressor if necessary, as explained above for Figure 2.

A number of gas cooling units 366, including gas compressor after coolers and gas export coolers, are also provided as part of the gas compression unit 360, so that the CNG can be delivered at the required temperature, again as explained above for Figure 2. For each scavenging compressor train, a knock out drum 367 is provided as part of the gas compression unit 360.

The PVs are hosted in the hold of the ship, and are therefore not visible in Figure 3. All accessory or secondary units are located on the deck, towards the forepart of the ship. These secondary units are: a fuel gas unit 420, which powers the gas turbines; a main electric power generation unit 470 that serves the whole ship; a chemical injection unit 120a, which is used to inject a chemical hydrates inhibitor into the CNG, namely methanol, when necessary; an inert gas unit 600, which is used to control the atmosphere in each sealed compartment containing PVs; a compressed air unit 460, which is necessary for the functioning of the scavenging gas turbines; a flare, vent and blow-down unit 230, connected with the various blow down pipes and systems on the ship - this unit also hosts a knock out drum; an emergency electric power generation unit 480; a diesel fuel unit 430, which powers the engines of the boat; a sea water unit 500 that is responsible for the provision of sea water to the sea water coolers (gas export coolers); a closed drain unit 550, which is emptied of its liquids at the delivery or loading locations; a hot water unit 410 that supplies the hot water heat exchangers; and a gas separation unit 300.

It seems optimal to reserve the aft of the ship for process units, whilst the fore is reserved for utilities.

Figure 4 summarises the relevant CNG management operations in connection with the operations of loading and, more importantly, unloading of CNG to and from the ship for the K delivery point case study.

Compressed Natural gas NG is first loaded from the FPSO onto the CNG carrying ship via loading and unloading system 170 (also referred to as gas sealine system). The gas is then stored in the gas storage system 361 , which comprises storage pressure vessels.

During spontaneous delivery, CNG is transferred from the PVs to a gas heating system 300, so that when the gas laminates it will still be delivered at the required temperature (thick solid line in Figure 4). The NG is then transferred back to the loading and unloading system 170 (thin solid line to the right of unit 300 in Figure 4), this time for unloading purposes, and from it to onshore facilities.

During delivery with compression (regimes b) and c) above), the NG is first transferred from the PVs to a gas compression system 360 comprising pre-heaters, compressors and coolers, as described in Figure 2. In the gas compression system 360, preliminary heating of CNG takes place (only for regime c)). The CNG is then heated and compressed according to upper loop 700 (see upper loop of thick dashed lines in Figure 4). Before the CNG is delivered, however, the CNG is transferred according to lower path 800 (see lower path of thick dashed lines in Figure 4) to bring the temperature of the CNG in line with the delivery point requirements. Lower path 800 involves cooling of the CNG through a gas export cooler unit 360.

In addition, Figure 4 shows the relationship between the above mentioned key units, part of the gas compression system 360, and the various secondary or utility units, such as the blow down system 230, the inert gas system 600, the methanol injection system 120, the closed drain system 550, the hot water system 410, the sea water system 500 and the fuel gas system 400.

Figure 5 is equivalent to Figure 2 and it is for the B delivery point. The B delivery point accepts CNG at higher temperatures, in the order of 20 degrees C.

The final step during regimes b) and c) of cooling the CNG down to meet the delivery point required temperature is therefore now superfluous, and consequently the gas export cooler is not present in Figure 5.

Figure 6 is equivalent to Figure 3 and it is for the B delivery point. The layout of Figure 6 only differs with the layout of Figure 3 for the absence of the two gas export coolers 366, part of the gas compression unit 360 in Figure 3. As a result, the ship is also slightly differently dimensioned compared to the ship of Figure 3.

Figure 7 is equivalent to Figure 4 and it is for the B delivery point. The block flow diagram of Figure 7 only differs in comparison with the block flow diagram of Figure 4 for the absence of the gas export cooling unit.

While Figures 5, 6 and 7 are only minimally different to Figures 2, 3 and 4, they demonstrate that systems according to the present invention can be tailored to specific applications. Such modifications will be generally dictated by the difference between the values of the pressure and temperature of the CNG at the loading location, and by the values of pressure and temperature required for the delivered CNG at the delivery location.

The pressure vessels have been disclosed to be for CNG, but it might be for carrying a variety of gases, such as raw gas straight from a bore well, including raw natural gas, e.g. when compressed - raw CNG or RCNG, or H ₂ , or C0 ₂ or processed natural gas (methane), or raw or part processed natural gas, e.g. with C0 ₂ allowances of up to 14% molar, H ₂ S allowances of up to 1 ,000 ppm, or H ₂ and C0 ₂ gas impurities, or other impurities or corrosive species. The preferred use, however, is CNG transportation, be that raw CNG, part processed CNG or clean CNG - processed to a standard deliverable to the end user, e.g. commercial, industrial or residential.

CNG can include various potential component parts in a variable mixture of ratios, some in their gas phase and others in a liquid phase, or a mix of both. Those component parts will typically comprise one or more of the following compounds: C ₂ H ₆ , C ₃ H ₈ , C ₄ H ₁₀ , C ₅ H ₁₂ , C ₆ H ₁₄ , C ₇ H ₁₆ , C ₈ H ₁₈ , C ₉ + hydrocarbons, C0 ₂ and H ₂ S, plus potentially toluene, diesel and octane in a liquid state, and other impurities/species.

The present invention mainly concerns medium to high pressure applications since it relates to the loading of the ship, the systems therefore, and the offloading systems. Due to the heavy nature of such pipes when made of steel, it is desireable to offer lighter alternatives. The present invention also provides lighter pipes, however, for lower pressure applications if desired.

Figure 18 shows a section of pipeline for transportation of CNG. The pressure of the CNG inside the pipe may be 250 bar, whereas the pipe may be designed to bear a pressure of up to 300 bar, or more - e.g. in excess of 1000bar.

The pipeline, of which the illustration shows only a short section, may extend for hundreds of metres, or further, and may be located on-shore, such as in a CNG distribution plant, or off-shore, such as on a platform for extraction of raw CNG. For the present invention it will be off-shore, e.g. on a buoy system, a platform or a jetty. Alternatively the pipeline may be part of a ship for transportation of CNG - i.e. part of the pipe network during loading/offloading. For example, it might be part of a system of pipes interconnecting pressure vessels located on the ship, which vessels are dedicated to the storage/transportation of the CNG on the ship.

High and medium pressure applications typically involve pipes that are required to withstand pressures in excess of 100 bar, and potentially pressures as high as 300 bar. Given these high pressures, the thicknesses of the walls of these pipes is generally very thick.

In general the wall thickness (t) of pipes, as a function of internal pressure (P), can be calculated by using the basic formula t = (Pd)/2o _y , where "d" is the diameter of the pipes and o _y is the strength of the material the pipes are made of (i.e. the yield strength for steel in the conventional pipes of the prior art, and the ultimate strength divided by a safety factor for composite materials). To provide an example, a range of potential diameters for CNG pipes in ships is typically between approximately 3 inches (7.5 cm) and 12 inches (30 cm). These dimensions are established on the basis of design considerations, i.e. the pipes are designed to carry prescribed quantities of CNG at the required pressures. These parameters determine the flow rate of the compressed gas and, therefore, the sizes of the diameters. In certain applications, diameters above 12 inches (30 cm) can be used.

For making these pipes, a typical material used in the industry is API 5L X52 piping steel. With that material, to achieve a desired safe maximum working pressure for the pipe, the typical pipe wall thicknesses in the industry would fall in the range of between 20 and 100 mm, depending on the pressure to be withstood. A substantial area of the overall pipe section is therefore comprised of steel. These steel pipes are therefore very heavy. If the same pipe with the same boundary conditions (e.g. pressure and temperature) is made out of carbon-based composite its thickness would be similar to a steel structure but having 1/3 to 1/5 of the total weight. If made out of glass-based composite its thickness would be up to twice the thickness of a metal structure, but having ½ of the total weight.

The length of pipe shown in Figure 18 is formed by welding two separate pipes 902, 903 together, along an annular weld line 905. One of the pipes 902, as shown on the right, is a seamless pipe, i.e. one made according to rotary piercing or the Mannesmann process. Pipes of this kind are well suited to this application because of the absence of seams along the length of the pipe. This makes it unlikely that defects would be present, or that defects would form, along the length of that section of pipe. The second pipe 903, on the left as shown, however, has been formed using a roll- technique, by bending and then welding the sides of a metallic plate together. This is another well practiced technique.

The material of the two separate pipes can be steel, such as carbon steel, due to it being relatively inexpensive and strong.

If the left-hand pipe 903 was to fail, it would probably do so along the weld line 904, due to the weld line being a potential weakness. Therefore, to compensate for that weakness, the left-hand pipe 903 has been over-wrapped with a resin impregnated tape containing carbon fibres. The wrapping has been installed over the inner pipe by a well known technique: fibre winding (or filament winding). The direction of the winding of the fibre 907 along the pipe 903 is represented schematically by the dashed line in Figure 18. This fibre winding is also known in the art as "hoop wrapping" - it takes the form of hoops that wrap linearly along the longitudinal length of the pipe in a generally uniform way, i.e. with a constant tension and a constant angle.

The fibres may be in the form of single fibres, a yarn or tow of fibres, or a tape of fibres.

Preferably the fibres abut one another on consecutive hoops - they are instead shown in an open hoop arrangement for maintaining the clarity of the drawing.

Since an internal pressure within the pipe, as applied by the pressurised CNG, would tend to open the pipe 903 along the weld line 904, it is the intention of the over- wrapping of the pipe 903 to ensure that that won't occur. The orientation of the reinforcement fibres is therefore preferably substantially perpendicular to the direction of the weld line 904. This maximises the hoop-strength of the over-wrapping, thereby maximising the efficiency of the provided reinforcement against those weld-bursting forces. By abutting the consecutive windings against one another, such perpendicularity of the windings can be maximised. Nevertheless, where a tape is used, the perpendicularity will inevitably be slightly compromised due to the more discernable width of that tape. Nevertheless, the perpendicularity will still be reasonably good. For example, assuming a variance from perpendicular of only 1 ° is acceptable, that can still be achieved on a 100mm diameter pipe, using a 5mm wide tape, where consecutive windings abut one another, and a 100mm diameter pipe. Further, for larger pipes, that variance can be achieved with wider tapes.

It is preferred that perpendicularity is maintained to at least an accuracy of 5°. Such an angle between the weld line 904 and the fibres of the over-wrapped layer of composite will not significantly compromise the hoop strength of the wrapping.

As mentioned above, the fibres may be single fibres, and such fibres would present a very close approximation to perfect perpendicularity, due to the thin nature of the fibres. However, to reduce the winding time (many thousands of fibre hoops will typically be wound around the pipe), the fibres are typically organised into a winding tape, or some other bundle of fibres, with that bundle of fibres then being wound around the pipe. Fewer actual windings therefore need to be undertaken since each winding lays down many fibres.

Within those bundles, it is preferred that the fibres are linearly arranged in a substantially parallel manner to one another, in the form of a thin strip. Bundles formed with straight parallel fibres can have a lower tendency to stretch due to there being no element of the fibres being available to straighten. However, other low-stretch arrangements for such bundles are also known in the art of fibre winding. For example, the fibres may be arranged in yarns, tows, braids and webs, potentially then with multiple of those arrangements being arranged to form a tape.

The fibres might even be woven to form a fabric or cloth of fibres.

To apply the fibres to the pipe, laying them down there along in hoops that align along the longitudinal axis of the pipe, a winding machine with a translating mechanical head may be used. It can be provided to deliver the fibres, or the tape 907, to the pipe 903 while the pipe rotates on or around its axis, such as by mounting the tape on an inner mandrel, or by rotating it via chucks positioned at the ends thereof.

Before winding the fibres or the tape around the pipe, the fibres are immersed in a resin bath. Alternatively, the resin may be pre-applied in a layer, or it may be sprayed as the fibres are applied onto the surface of the pipe.

The outcome of the deposition of hoops of resin impregnated fibres on and around the pipe is a layer, or layers, of fibre-reinforced polymeric material. These can be built up by consecutive layering (e.g. by winding back-and-forth) so as to provide an overall thickness such as to allow the layers together to contribute structurally to the performance of the pipe.

In Figure 18, the over-wrap layer of fibre reinforced polymer can have a thickness in the range of between 3 and 40 mm.

However, in certain other applications, a thinner layer of metal may be preferred to the thick pipe 903 of Figure 18. That thinner layer can again be over-wrapped with fibre-reinforced polymers, so as to form one or multiple layers of composite material over that inner layer of metal. To provide adequate strength to the pipe, the layer(s) of composite will need to be thicker since the metal layer offers less strength than before.

This alteration in the design can even be taken further such that the thinner layer of metal ends up offering little or no structural strength to the pipe. Such a metal liner would be self supporting, and would withstand the forces of winding. However, they need not have sufficient strength to offer a significant contribution towards the pressure withstanding capabilities of the pipe, once formed, i.e. the composite layer(s) would provide that capability. The function of the liner would then be restricted, effectively, to 1 . providing a mandrel over which the fibre can be wound, and 2. providing containment of the CNG - a metal liner is typically less porous than the fibre reinforcement. Typical liner thicknesses can be in the range of between 0.5 and 2 mm.

Liners can be formed like normal pipes, i.e. they can be side-to-side welded, as shown for the left-hand pipe 903 in Figure 18.

Reverting to the fibre-reinforced polymer used to surround the pipe 903, or the liner, possible fibres that can be used within the invention include at least carbon fibres, glass fibres and Kevlar® (a commercial name for a specific type of aramidic fibre). Accordingly, the outer materials will be, respectively, carbon fibre reinforced polymers (CFRP), glass fibre reinforced polymers (GFRP) or Kevlar® (aramid) reinforced polymers (KRP).

Hoop wrapping of traditionally formed seamed pipes can be enough to reinforce the pipe, or to allow the manufacturer to produce equivalent pipes with less structural steel or metal. However, hoop wrapping will not be sufficient or adequate for reinforcing or coating a pipe with an end-to-end weld 905, like the one shown in Figure 18 for joining two pipes 902, 903 together. For that, a different approach is needed.

According to this aspect of the present invention a reinforcing patch 906, made of a fibrous material, is installed over the weld, as also shown in Figure 18. It covers the end-to-end weld 905, and part of the ends of the two pipes 902, 903.

It is essential that the patch 906 contains fibres that are oriented at least with a significant transversal component, i.e. at least at a 45° angle to the transverse weld. Preferably it has fibres that extend substantially perpendicular to the weld, i.e. to at least 5° of perpendicular. As such they extend substantially transverse to the direction of the weld 905, or parallel to the longitudinal axis of the pipes 902, 903 (due to the transverse nature of the weld 905). This orientation allows the fibres to contribute their tensile strength to the end-to-end weld 905 so as to increase the strength of the pipe 901 at that point in the direction of the axis of the pipe 901 .

In this embodiment, the patch 906 is a woven cloth, mat or fabric sheet, for example made with intertwined fibres.

A preferred material that can be included in the patch 906 is a woven roving fabric of fibres. A woven roving fabric of fibres is made of intertwined bundles (roving) of fibres. Each bundle or roving is untwisted, so that it can easily be impregnated by resins.

Roving fabric may also be comprised within the over-wrap 907.

On a reference plane, the woven roving fabric of fibres provides a suitable fibre strength substantially along any direction in the plane. This is because of the presence of fibres within the patch 906 in two, transversely arranged directions, i.e. at 90° to one another. These are often referred to as the "weft" and the "warp". The fabric of this type can thus be laid onto the weld 905 in any orientation within that reference plane and still offer the desired strength contribution to that weld 905 for reinforcing the end-to- end weld 905.

The patch, or the reinforcement sheet 906, in practice, would typically be wrapped as a single elongated sheet around the full circumferential extent of the weld 905, i.e. so as to extend around the whole circumference of the pipe 901. The sheet 906 would additionally extend sideways from the weld 905 onto both pipes 902, 903 so as to covers a length of the welded ends of both pipes 902, 903, whereupon the weld is bridged by the reinforcement 906. Then, as shown in Figure 19, the over-wrap composite layer would wrap over that reinforcement sheet to hold it down over the joint.

Figures 19 and 20 show two different arrangements for the over-wrap with respect to the reinforcement sheet 906. In figure 19, the sheet 906 is given the reference sign 916. In figure 20 it is given the reference sign 936.

Referring first to Figure 19, there is shown a thin metallic liner 921 , made of a CNG resistant and CNG impermeable metal, such as stainless steel. As with Figure 18, it is formed as two pieces 912, 913 with a weld therebetween. It therefore has an end- to-end welding line 915 extending around the full circumference thereof. A composite reinforcement patch or strip 916 has then been wound around the weld 915. The composite patch 916 contains a woven roving fabric made with Kevlar® (aramid) fibres. Some of the fibres are disposed with a transverse component with respect to the weld 915.

The reinforcement 916 is only for strengthening the weld 915 between the tubular liners 912, 913.

To provide the pipe with structural hoop-strength properties, a composite over- wrapping 918 is additionally provided. The composite over-wrapping 918 has been deposited by winding a carbon fibre tape, previously impregnated with an epoxy resin, around the liner and over the strip of reinforcing material 916. Because the tape is gradually wound around the liner 921 to form the final pipe 91 1 , an overall uniform thickness for the pipe wall can be obtained. To do this, a thinner layer of the composite material is wound over pipe at the location of the strip 916, while a thicker layer of that composite material is wound around the rest of the liner, i.e. on either side of the reinforcing strip 916. In Figure 20, a slightly modified embodiment compared to Figure 19 is shown. Two pipe liners 932, 933 are again welded together to form a weld line 935, and a reinforcing strip 936 is again wrapped around it. However, in this embodiment the over- wrapping layer of composite material 938 is wrapped over the reinforcing strip 936 in a manner to retain a substantially constant minimum thickness for that composite material 938 even over the area of the pipe 931 featuring the reinforcing strip 936. This results in a pipe 931 having non-uniform wall thickness, and a visible bump over the reinforcing strip 936. This may be useful for identifying the location of the weld 935.

In these two embodiments, the liners 912, 913, 932, 933 may be 5 mm thick steel pipes, the fibres may be glass fibres and the resin may be an epoxy based resin. Further, the reinforcing strip 916, 936 may be 10 mm thick, while the layer of composite 918, 938 may nominally be 15 mm thick.

In the embodiment of Figure 21 , a composite reinforced pipe 951 is suspended 954 on a bracket 953. The pipe 951 is part of a network of pipes for CNG conveyance located onboard a ship. The bracket 953 rakes a form of a clamp, or compressive ring, that surrounds the pipe along the whole circumference thereof. Such clamps are relatively standard for pipe hangers, and can be acquired as a stock item.

The width w of the clamp determines the contact area 956 of the support on the pipe 951 .

Pipe clamping equipment and prior art pipes are usually both made of metal - for example steel. For the prior art pipes, due to their wall thickness being so thick, little if any accommodation was available for mal-aligned clamps, in terms of compression of the pipe's outer surface, i.e. compliance, and as a result of that the pipe clamping equipment would tend to contact the pipe over a small area - smaller than the internal surface area of the clamp, i.e. just the points or lines of contact. This is shown schematically in Figure 22 with the high-peaking line - the smaller area leads to high peak stress o _m for a given clamping force. The pipe of the present invention, however, is coated with a reinforcing layer of fibre reinforced polymeric material 952. Further, the compression strength of the composite material is likely to be lower than that of the metal of the prior art pipes. As a result, the contact stresses for a given supporting force are likely to be distributed over the whole contact area of the support, as defined by the width w of the clamp. Therefore, a lower peak stress o _c will occur, as also shown, by comparison, in Figure 22. Because of the structural function of the composite layer in these applications, i.e. the requirement for this layer to carry all or part of the load generated by the internal CNG pressure, the preferred matrix material will be a thermosetting resin as opposed to a thermoplastic resin. In the embodiment of Figure 21 , a polyester resin was used. Thermosetting resins typically are about 5 times stronger than equivalent thermoplastic resins.

It is noted that thermoplastic resins are more suited to be used as an interface with a gas, because of their higher degree of impermeability. However, in the applications described here, impermeability is provided by the inner liner or layer of structural metallic material. Thermosetting resins are thus still preferred due to higher mechanical properties, although in practice either could be used.

Additional advantages related to the composite material wrapped around the pipes of the present invention are:

1 . An increased thermal insulation of the pipes with respect to the outer environment. This is a by-product of the overall lower degree of thermal conductivity of the composite materials compared to metals;

2. An inert coupling of the pipes with the support at the clamping points, i.e. no, or little, potential for electrochemical activity. This is a by-product of the fact that the composite acts as an electrical insulator, thereby limiting any opportunity for galvanic couplings to exist between the pipes and their supports, in the presence of potentially salty water. This property, however, may be present for only certain resin/fibre combinations, for example glass fibre reinforced composite plastics. After all, carbon fibres may allow the composite to function as a conductor.

3. The pipes of the present invention are particularly damage tolerant. Damage tolerance is a property that is intrinsic in many composites, and is a desired property for the composite layers that cover the pipes of the present invention. Metals can fail catastrophically, i.e. without any significant warning, when they reach their ultimate strength, or when defects such as cracks or corrosion have developed. Crack propagation in metals is usually unstable and unpredictable. With the present invention, however, the mode of failure will tend to give more forewarning. For example, cracks or corrosion pitting may occur in the inner surface of the pipes, e.g. due to the chemical aggressiveness of the CNG. That cracking and/or pitting will then be accelerated by the high internal pressure of the CNG. When the resisting wall thickness reaches its limit, due to the fact that it has been eroded or damaged by the cracking and/or pitting, failure may occur suddenly and violently in a solid metal pipe. This is referred to herein as a catastrophic failure. With the present invention, however, there is an external layer of composite material, and this will work as a barrier against catastrophic failure. Because of the discontinuity between the metal and the composite, cracking and pitting are unlikely to propagate rapidly across from the metal into the composite. Further, the composite can resist a certain degree of delamination anyway. As a result, the regular inspections that need to be carried out on such pipework would be able to identify a deterioration before the pipe bursts, e.g. there may be swelling or discolouration of the outer surface of the pipe. This is explained further below.

Figure 23 illustrates an embodiment of pipe 961 in which visual inspection of possible internal damage in a layer of the composite material is possible. In this example, an inner layer of CNG resistant and CNG impermeable material (a metallic liner 964) is covered with three layers 965, 966, 967 of composite material. The first layer 965, closest to, and in contact with, the liner 964, is a resin rich layer of composite material. The next layer - the intermediate composite layer 966, is then somewhat less rich in resin than the inner composite layer 965, but it is richer in its fibre content. The final, or outer composite layer 967 is then even richer in fibres, and less rich in resin. Other arrangements are possible, although this arrangement is preferred.

In this embodiment the resin is a translucent resin. Further, the fibres are glass fibres - translucent glass fibres. The fibres have been wound around the pipe such as by a method as explained above, i.e. by fibre winding. However, the resin percentage in the three layers will have been altered during that wrapping process, such as by dipping the fibre tapes in a resin bath for longer or shorter time periods.

With this translucent arrangement, if a fracture, crack or pit propagates through the liner's wall 964 and eventually affects the composite layer, it will first impact the resin rich layer 964. This might already be visible externally of the pipe, e.g. through the three layers. However, upon the damage propagating through the first layer 964, it will become increasingly visible.

By providing the first layer in the form of a resin rich layer, the propagation of damage through that layer will typically occur by a mechanism called "material crazing". Crazing is a known and documented mechanism of failure of a plastic material, such as a composite resin, whereby a network of fine cracks and gaps develop in the material. The cluster of micro-voids 975 and small fibrils 974 that is characteristic of crazing can be seen schematically in Figures 24 to 26. Tiny voids 975 and filaments of polymer 974 precede the generation of a fracture - two distinct lips 972, 973 in the material are a sign of a fracture being formed. Crazing is most evident in the direction of propagation of the fracture 976, and results into a local step change of the optical properties of the layer of composite (for example its coefficient of diffraction or coefficient of reflection is changed). This effect can be exploited visually upon inspecting the pipes from the pipe's outside surface, whereby the damage can readily be identified.

In practice the crazing leads to white or opaque spots, lines or blotches within the composite, which marks are very easily seen.

With the translucent resin, and potentially also the translucent fibres, the tendency of the composite to craze upon damage occurring within the pipe allows an operator to be readily trained to detect potentially hazardous damage to the pipe by looking for changes in the optical properties in the pipe, such as this "white spotting". Whether the spots will actually be white, however, will depend upon the colour of the resin/glass or the colour of any leaked fluid into the cracks.

This aspect of the present invention therefore allows a potentially leaking or failing region within the pipe to be recognised by virtue of it being an area which exhibits an anomalous or discontinuous look or coloration.

In this embodiment of the invention, it is also to be observed that the layers arrangement also makes the pipe less likely to fail catastrophically, without prior warning, thereby allowing additional time for pipe replacement or repair. Plant down times are therefore reducible (since minor damage is easier to repair than catastrophic failures), and further the repairs can be more conveniently scheduled, rather than having to be done immediately following a catastrophic failure.

The pipes may be able to carry a variety of gases, such as raw gas straight from a bore well, including raw natural gas, e.g. when compressed - raw CNG or RCNG, or H ₂ , or C0 ₂ or processed natural gas (methane), or raw or part processed natural gas, e.g. with C0 ₂ allowances of up to 14% molar, H ₂ S allowances of up to 1 ,000 ppm, or H ₂ and C0 ₂ gas impurities, or other impurities or corrosive species. The preferred use, however, is CNG transportation, be that raw CNG, part processed CNG or clean CNG - processed to a standard deliverable to the end user, e.g. commercial, industrial or residential.

CNG can include various potential component parts in a variable mixture of ratios, some in their gas phase and others in a liquid phase, or a mix of both. Those component parts will typically comprise one or more of the following compounds: C ₂ H ₆ , C ₃ H ₈ , C ₄ H ₁₀ , C ₅ H ₁₂ , C ₆ H ₁₄ , C ₇ H ₁₆ , C ₈ H ₁₈ , C ₉ + hydrocarbons, C0 ₂ and H ₂ S, plus potentially toluene, diesel and octane in a liquid state, and other impurities/species.

The present invention is described below mainly in relation to CNG applications. It will be appreciated, however, that this will not affect the general applicability of the invention, which is applicable to the delivery of numerous other fluids.

Referring to Figure 27, there is illustrated a section of pipe 1010 which is part of a low pressure distribution pipe network for distributing CNG to utility points. Traditionally, such pipes are made of metal, usually steel. The pipe of Figure 27 replaces the traditional steel pipes. The pipe 1010 has an outer structural shell 1003 made of a thermosetting plastic material (a thermoset plastic). In preferred embodiments, the material uses a resin calleds DCPD. However other polymeric thermosetting materials are useable too, such as polyester and epoxy, with this not being an exhaustive list.

The choice of the polymeric material depends on the required ultimate tensile strength (or hoop strength).

It is know that thermosetting polymers have, in their in-use status, i.e. once cured, an ultimate tensile strength (o _t hermosettin _g ) that can be in excess of 50 MPa. This is in contrast with the tensile strength of thermoplastic materials (othermopiastic), which in most cases does not exceed 20 MPa. Indeed, the tensile strength of certain thermosetting materials, notably DCPD (O _D CPD), can be in excess of 80 Mpa, depending on the quality of the polymerisation and the curing process. These thermosetting materials, therefore, have typically got a stronger strength for a given wall thickness.

However, thermosetting plastic materials involve a certain degree of molecular crystallisation and - for this reason - do not guarantee, at least under certain commonly experienced pipe-pressure conditions, full impermeability in respect of contacting fluids or gases. In other words they would be likely to leach (or leak) some of the content of the CNG (such as the smaller molecular constituents) into the atmosphere (or the surrounding area of the pipe). Certain thermoplastic materials, on the other hand, are generally amorphous, which gives them their comparatively higher degree of impermeability to fluids such as CNG. Therefore, for CNG applications, thermoplastic materials would provide a proven barrier against CNG penetration and leakage. However, they have not been used in such applications due to their generally unacceptable mechanical properties in these applications - they would be too weak to withstand the required transportation/distribution pressures (e.g. 95 bar). In consideration of the above, and taking into account the operating pressure of medium to low pressure CNG lines (typically 30 to 100 bar), traditional pipes for the transport and distribution of CNG have been made of steel. Replacement with lighter, cheaper pipes made of plastics has never been contemplated, or at least it has never been achieved in a useful manner. On the one hand, thermoplastic materials would have been mechanically too weak. On the other hand, thermosetting materials would have been too permeable, even though an acceptable strength might have been provided.

The present invention therefore overcomes the deficiencies in known plastics pipes by providing a pipe 10 as shown in Figure 27. It makes use of an internal substrate or layer 1005 of metal (nickel in this case, but other metals are possible including all the metals traditionally used for electroplating applications such as copper, and other metals such as aluminium). That layer is to provide the required CNG impermeability, and also a resistance to chemical attack.

The average external diameter of the pipe can be any conventional size, including 20mm, 25mm, 32mm, 50mm, 56mm, 63mm, 75mm, 90mm, 1 10mm, 125mm, 160mm, 200mm, 250mm and 315mm. However, it is preferred to be up to about 10 cm.

The average thickness of the wall can also vary, depending upon the diameter of the pipe, or the required pressure containment, but the thickness will typically be chosen within a range of about 5 to 30 mm. The lower the operating pressure, and the smaller the diameter, the lower the required pipe wall thickness.

In general, the wall thickness (t) of pipes as a function of internal pressure (P) can be calculated by using the basic formula t = (Pd)/2o _y , where "d" is the diameter of the pipes and o _y is the yield strength (ultimate strength if a polymer) of the material the pipes are made of.

To provide an example, the range of possible diameters for CNG pipes in CNG low pressure applications (up to 100 bar, or often up to just 75 bar) is typically between approximately 0.5 inches (1 .25 cm approx.) and 4 inches (10 cm approx.). These dimensions are established on the basis of design considerations, i.e. the pipes are designed to carry prescribed quantities of CNG at the required pressures. These parameters determine the flow rate of the compressed gas and, therefore, the sizes of the diameters. In certain applications, diameters above 4 inches (10 cm approx.) can be used. Consequently, on the basis of the given pressures, typical pipe wall thicknesses in the CNG industry - low pressure applications - fall in the range between approximately 1 and 15 mm, depending on the exact pressure or pressure range to be supported.

The thickness of the metallic layer will also be determined by the precise application. Factors such as CNG purity, CNG pressure and flow rate will affect the required thickness. It is however envisaged that in most applications a thickness of up to 0.5 mm (500 microns) will suffice.

The outer shell 1003 of the pipe, i.e. the plastic part, can be manufactured in a variety of manners. One simple method of manufacture is rotational moulding.

Many methods of deposition of the metallic substrate 1005, layer or film are also possible. One is spray coating. However, electrolytic deposition (similar in principle to electrogalvanization) can also be applied. This is particularly suitable for applications where the thickness or average thickness of the layer is desired to be particularly small, e.g. perhaps 5 to 50 microns.

One preferred method of manufacture of the above metallic internally coated thermosetting plastics pipe is illustrated with reference to Figure 28. The method is entirely chemical and does not require any electrical power input.

The pipe 1020 is filled with an electroless solution 1018 (horizontal shading in Figure 28). The electroless solution contains a reductive agent. The reductive agent is responsible for the reduction and solidification 1015 of ions 1017 of the metal within the solution 1018, which form clusters 1015 of metallic deposit on the wall 1013 of the pipe 1020. Such ions 1017 are initially dissolved in the electroless solution, or can be dissolved therein from a metallic electrode which is in contact with the bath (not shown).

The process can be boosted by initial preparation of the pipe cavities, such as by cleaning or ultrasonic cleaning - removal of any form of dirt or impurities will be highly beneficial for a successful deposition and adhesion, of the metal on the inside of the pipe.

The process can also be boosted by adding to the electroless solution a chemical catalyst for the reduction reaction responsible for the deposition of the metal.

Among other methods that can be used for manufacturing the metallically internally coated thermosetting plastics pipe of the present invention is plasma coating.

Such methods for coating plastics with a metal layer are well known to production engineers, and thus need no further discussion herein. Referring now to Figure 29, a modified pipe is shown. The pipe has a joint 1030 realised between two metallically coated pipes, each made of an external thermosetting plastic material 1033, and an internal layer 1035 or film made of a metallic material.

Each pipe comprises, at one end thereof, a flanged portion 1036 or flanged end, which makes connection of the pipes possible by applying bolts 1038 or other retaining or securing means, though holes in the flanges as shown in Figure 29. Typically at least two such holes are provided, and an o-ring may locate between the facing surfaces of the flanges to provide a good seal therebetween. In higher pressure applications, however, including many applications where CNG is being distributed, multiple such holes, and multiple such o-rings may be desired. For example, eight circumferentially spaced holes may be provided in each flange.

Although a preferred flange arrangement is shown and described, it will be readily apparent to a skilled person that the pipes can instead be joined according to any other method known in the art, for example by using press or push fittings, or other mechanisms by which the interfaces 1037 to be joined/sealed together are so joined/sealed, e.g. by way of a suitable connection or joining means, such as portions that can be snap fitted to each other.

The above description has concentrated on industrial CNG applications. However, it is clear that the pipes and piping systems of the present invention can also be successfully employed in domestic environments, for example for domestic delivery of natural gas. Domestic natural gas pipes are usually made of copper. There are however examples of domestic natural gas pipes made of thermoplastic materials such as PE or MDPE. Domestic natural gas pipes typically connect a gas delivery point (the point where the gas is metered) with a gas appliance such as a boiler or gas cooking range.

The pipes, and particularly copper pipes since they are typically less flexible than plastic ones, have lots of joints, and it would be desired to make each joint inspectable.

The pipes of the present invention may successfully replace these traditional domestic gas pipes. They would be sufficiently impermeable to be suitable for the application. Further, they would be lighter and cheaper to manufacture compared to existing copper pipes. They would also be stronger than current pipes made of a thermoplastic material, such as PE and MDPE (medium density polyethylene) pipes. Configurations where less joining is required are also possible. For example, an elbow can be integrally formed in a pipe, rather than being formed by means of an elbow joint.

An additional but considerable advantage connected with the pipes of the present invention arises when the thermosetting material is translucent (or even better transparent) to light. Thermoplastic plastic materials are typically generally opaque to the light, due to their amorphous structure. Thermoset plastics, however, can be provided as a translucent material.

If the external shell of the pipe is translucent or transparent, the internal layer or film of metallic material can be inspected from outside of the pipe, and defects such as cracks, delaminations, deposition defects, metallic layer porosity or pitting and metallic layer corrosion can potentially be easily detected without any internal inspection (internal inspections being something that is difficult or costly to arrange).

These new pipes can carry a variety of gases, such as raw gas straight from a bore well, including raw natural gas, e.g. when compressed - raw CNG or RCNG, or H ₂ , or C0 ₂ or processed natural gas (methane), or raw or part processed natural gas, e.g. with C0 ₂ allowances of up to 14% molar, H ₂ S allowances of up to 1 ,000 ppm, or H ₂ and C0 ₂ gas impurities, or other impurities or corrosive species. The preferred use, however, is CNG transportation, be that raw CNG, part processed CNG or clean CNG - processed to a standard deliverable to the end user, e.g. commercial, industrial or residential.

CNG can include various potential component parts in a variable mixture of ratios, some in their gas phase and others in a liquid phase, or a mix of both. Those component parts will typically comprise one or more of the following compounds: C ₂ H ₆ , C ₃ H ₈ , C ₄ H ₁₀ , C ₅ H ₁₂ , C ₆ H ₁₄ , C ₇ H ₁₆ , C ₈ H ₁₈ , C ₉ + hydrocarbons, C0 ₂ and H ₂ S, plus potentially toluene, diesel and octane in a liquid state, and other impurities/species.

The present invention as described above therefore provides numerous advantages over both prior art metal pipes, and prior art plastic pipes.

The present invention has been described above purely by way of example. Modifications in detail may be made to the present invention within the scope of the claims appended hereto.