CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 1 19(e) to U.S. provisional patent application No. 62/355,146 filed June 27, 2016.

FIELD OF THE INVENTION

The present invention relates to reinforced flexible pipes and more particularly to reinforced, polymeric pipe.

BACKGROUND OF THE INVENTION

Flexible, polymeric pipes are employed for conveying fluids under pressure such as natural gas, sour gas, carbon dioxide, hydrocarbons, etc.

It is desirable that the pipe be capable of being spooled, handled, bent, etc. substantially without collapsing, buckling, splitting, cracking, etc., even in low temperature environments, yet also be capable of containing high pressure flows at elevated temperatures under conditions of use, such as when buried, unrestrained and bent.

While these pipes are intended for conveying fluids, some fluids such as gases may permeate through the pipe wall. In some applications these permeated gases may build up in the wall and can cause failures, Gas permeation is therefore a concern in the use of flexible pipe.

SUMMARY OF THE INVENTION

A flexible, fiber reinforced pipe for transporting pressurized fluids. The pipe is flexible enough to be spooled for transport, handling or storage, even under colder winter conditions, but has sufficient performance properties to withstand typical loading when carrying pressurized fluids. In one aspect, the pipe has an inner tubular layer made from a polymer, a reinforcing layer, venting elements, and an outer sheath. The inner tubular layer can act to contain the fluid passing through the pipe, preventing it from leaking or diffusing through pipe. The reinforcing layer acting to react to radial and axial loading imposed on the pipe. Venting elements may comprise of a venting channel and a venting structure, the venting structure including a metal cord or a smooth surface polymeric rod. Venting elements permit gases that permeate into the space between the layers to be released through the pipe fittings. The outer sheath holding the venting elements in place and protecting the pipe from the outside environment.

In accordance with one aspect, there is provided a flexible polymeric pipe comprising: an inner tubular layer with an inner surface defining an inner diameter through which fluid can flow and an outer surface, the inner tubular layer formed of a plastic and having a length; a reinforcing layer formed of fibers, the reinforcing layer surrounding the inner tubular layer; venting elements including a venting channel alongside a smooth surface side wall and a non-compressible venting structure, the venting elements extending longitudinally along the length; and an outer sheath with an inner surface and an outer surface, the outer sheath enclosing the inner tubular layer, the reinforcing layer and the venting elements.

It is to be understood that other aspects of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein various embodiments of the invention are shown and described by way of illustration. As will be realized, the invention is capable for other and different embodiments and its several details are capable of modification in various other respects, all without departing from the spirit and scope of the present invention. Accordingly the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring to the drawings wherein like reference numerals indicate similar parts throughout the several views, several aspects of the present invention are illustrated by way of example, and not by way of limitation, in detail in the figures, wherein:

Fig. 1 is a side view of a pipe in a first aspect, partially cut away, in successive layers;

Fig. 2a is a sectional view of the pipe of Fig. 1 along line A-A;

Fig. 2b is a sectional view through another pipe, the section being the same as that shown in Fig. 1 as line A-A;

Fig. 3 is an enlarged view of area B of Fig. 2a;

Fig. 4 is an enlarged view of area C of Fig. 2a;

Fig. 5 is an enlarged view of area D of Fig. 2b; and

Fig. 6 is an enlarged view of area E of Fig. 2b.

Fig. 7 is a graph that illustrates the annulus flow versus the thickness for various polymeric inner layers.

Fig 8 is a graph that illustrates the annulus flow versus the pipe length for various pipe configurations.

Fig 9 is a sectional view through another pipe, the section being the same as that shown in Fig. 1 as line A-A;

DESCRIPTION OF VARIOUS EMBODIMENTS

The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments contemplated by the inventor. The detailed description includes specific details for the purpose of providing a comprehensive understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.

Figs. 1 and 2a illustrate a flexible, polymeric, fiber reinforced pipe 10 capable of transporting pressurized fluids, such as oil, gas, water, oil emulsion, etc. The pipe 10 has an inner tubular layer 20, a reinforcing layer 30, an outer sheath 50 and venting elements 60 and 70. The inner tubular layer 20 may have an inner surface 22, defining an imier diameter D, and an outer surface 24. The reinforcing layer 30 may surround the inner tubular layer 20, typically in contact with the outer surface 24 of the inner tubular layer. The venting elements 60 and 70 are in the pipe wall outwardly of inner surface 22. The outer sheath 50 surrounds the reinforcing layer 30 and the venting elements 60 and 70. In particular, reinforcing layer 30 and venting elements 60, 70 are in the annulus between layer 20 and sheath 50. In one aspect, the outer sheath 50 can define the outer surface of the pipe, for example, being exposed directly to the environment surrounding the pipe 10, Alternately, there may be a coating on the outer sheath. There can be other layers as desired, for example, any pipe may include one or more of: outer insulation, inner coatings or other layers such as barrier layers or further reinforcing layers, between layers 20 and 50.

The pipe is substantially uniform in construction along its length.

The inner tubular layer 20 defines inner diameter D of the pipe, through which fluids flow and therefore layer 20 acts as a leak bladder and liner to contain the fluid passing through the pipe 10, The inner tubular layer 20 can be formed of a plastic, such as a thermoplastic or elastomer. The plastic making up the inner tubular layer 20 can also be selected with regard to materials being conveyed, environmental conditions, cost, etc. In some high temperature applications, for example, the plastic can be selected to retain significant mechanical properties as the service temperature is increased from 60°C to at least 82°C. In those applications, critical properties may be a tensile strength at yield of approximately 1500 psi or greater at 82°C, as well as appropriate compressive creep resistance at 82°C wherein tensile strength is measured using ASTM D638 at a cross head speed of 2 inches/minute.

Possible plastics forming the inner layer 20 include one or more of: HDPE (high density polyethylene), HDPE with additives to increase the high temperature performance, such as bimodal HDPE-RT, PEX (cross linked polyethylene) possibly with silane cross linking, peroxide cross linking or radiation cross linking, PPX (cross linked polypropylene), PVDF (Polyvinylidene fluoride), PPS (Polyphenylene sulfide), PEEK (Polyether ether ketone), and PEK (Polyether Ketone), polybutene, polypropylene (such as one of an impact copolymer, a random copolymer, homopolymer, nucleated homopolymer, high crystalline polymer, high crystalline copolymer, etc.), polypropylene based thermoplastic vulcanizates, thermoplastic polyester, thermoplastic polyurethane, rubber, nitrides or nylon. In one embodiment, a HDPE-based layer 20 provides good handling and performance in many applications such as in the conveyance of water, oil and gas. Materials other than HDPE may be used, such materials may have progressively higher strengths and permeation resistances but may cost more, and may not possess low-temperature impact toughness and or the ability to be co-extruded, as depicted in Fig. 9, with permeation blocking materials.

In an aspect, additives such as stabilizers, antioxidants, fillers, process aids, compatibilizers, etc. could be added to plastic.

The inner tubular layer 20 should be as impermeable as possible to the fluid passing through the pipe 10 to prevent that fluid from leaking through the inner tubular layer 20 and into the reinforcing layer 30. In some cases, however, the inner tubular layer 20 still may allow some gas diffusion therethrough. The present invention attempts to minimize gas permeation and/or evacuate permeated gases to improve pipe performance. In one embodiment, for example, inner tubular layer 20 is configured by construction or composition to resist gas permeation.

For example, layer 20 may be selected to have a thickness that resists permeation. While the inner layer has a thickness to provide durability and to contain the pressures intended, the layer 20 may be selected to have an additional 30% thickness over what is required for typical operation to a) increase resistance to collapse when exposed to external pressure, and (b) further slow permeation of gas from the bore of the pipe into the annulus.

Additionally or alternately, layer 20 may have a polymeric composition selected to resist permeation. For example, layer 20 may be constructed with a polymer having a crystalline structure more resistant to permeation than a standard form of that polymer. For example, the polymer may contain a nucleating agent to promote crystal growth, for example by providing nucleating surfaces on which selected polymeric crystal growth can occur. The polymer forming layer 20 may, therefore, have a larger number of crystals 80 than a non-nucleated form of the polymer and/or the polymer may have a selected crystal form or orientation different than the standard crystallization properties of that polymer. In one embodiment, nucleating agent is used to slow gas permeation by increasing the tortuosity of permeation paths through the polymer. In particular, gas tends to permeate through a polymer at the interfaces between crystals. The formation of a radially indirect, such a tortuous, path between crystals, slows gas permeation through the polymer. Depending on the mode of operation of the nucleating agent, layer 20 may be comprised of a polymer having crystals: (i) with alignment substantially orthogonally to a radial path through the layer, (ii) having crystalline shapes that are plate-like being broad and flat with a width and breadth much larger than their thiclcness and/or (iii) out of alignment and overlapping in the radial direction such that only a tortuous path is available for gas permeation between the crystals. Low permeation and high barrier performance can be provided as a result of the degree of crystallinity and crystalline form of the polymer. High crystallinity may decrease the permeability of fluids across the inner layer 20.

In one embodiment, layer 20 includes a base of HDPE and contains a nucleating agent. In another embodiment, layer 20 is produced using a mineral-based nucleating agent, such as one sold under the trademark, Hyperform® HPN-20E by Milliken & Company or Ravago Crystaladd ^{1 M} , grade HM-237 NAT™. The nucleating agent has been shown to raise the crystallization temperature of linear low-density polyethylene from 109 °C to 113 °C.

In another embodiment, the inner layer 20 may contain materials that have greater resistance to gas permeation than other polymers. These polymers may exclusively form layer 20 or may be incorporated with other polymers as a blend or as a laminate layer as demonstrated in the illustrated embodiment of Fig. 9. Such gas permeation resistant materials may include for example aluminum, nylon, poly(vinylidene fluoride) or poly (vinylidene difluoride) (PVDF), ethylene vinyl alcohol copolymers or vinylidene chloride (EVOH). In one embodiment, for example, layer 20 is a laminate formed of distinct layers that may be unbonded or bonded together using an adhesive, such as of a resin 23. . In one embodiment, adhesive may be used between the layers to prevent delamination or collapse of the inner layer 20 under rapid gas depressurization conditions. In such an embodiment, inner and outer laminate layers 25a, 25b, respectively, may include a polymer, for example a high density polyethylene, and middle laminate layer 21 may be of a more expensive, gas permeation resistant material such as for example, aluminum, or EVOH. In one embodiment, the inner layer 20 may include an EVOH layer 21 sandwiched and protected between layers 25a, 25b of another plastic 26, for example, high density polyethylene. The layers may be amenable to extrusion at reasonably low processing temperatures

The reinforcing layer 30 surrounds and is positioned radially outwardly of the outer surface 24 of the inner tubular layer 20. The reinforcing layer 30 can be made up of reinforcing fibers which are substantially continuous along the length of the pipe. The reinforcing layer 30 may have an inner surface 32 and an outer surface 34. Reinforcing layer 30 may actually include a first reinforcing layer and a second reinforcing layer and possibly further layers. The fibers in the reinforcing layers 30 react to axial and radial loads on the pipe 10. Primary load is in the fiber tensile direction because little side load is typically induced under normal operating conditions of the pipe 10. The present pipe 10, being used to contain pressurized fluid with the prominent condition being internal pressure containment, can have the fiber chosen to favor the radial tensile direction. Other factors such as installation pull force (axial loading) and loads from spooling and unspooling for transport and installation in the field can also be taken into account for the fiber choice. The fibers in the reinforcing layers may be selected from one or more of various materials, such as glass (such as E-glass, E-CR glass, or S-glass), carbon, nylon, polyester, aramid, metal, or other suitable material with sufficient tensile strength. The material forming the fibers can also be chosen based on its resistance to chemicals, such as hydrocarbon and water that may come into contact. with the pipe 10 during its use. Additionally, the fibers could be used as single strands or could be combined, as by twisting or braiding with other fibers to form yarns made up of bundles of fibers which are then wound helically around the inner tubing layer 20 to form the first reinforcing layer or wound around the first reinforcing layer to form a second reinforcing layer.

In an aspect, the reinforcing layer 30 includes helical clockwise and counterclockwise windings of unbonded, unencapsulated fibers that are substantially free floating between the inner tubular layer 20 and the outer sheath 50 with no bonding to adjacent fibers. In this manner, the separate fibers in the first reinforcing layer and the second reinforcing layer remain independent and can react to loads in conjunction with each other rather than as a single rigid body. In another aspect, the fibers of the reinforcing layers 30 can be wound over the inner tubular layer 20 when the inner tubular layer 20 is in the soft or semi-uncured state, causing the material of the inner tubular layer 20 to partially mold around and adhere to some degree to the fibers of the reinforcing layers 30.

The reinforcing layer 30, provides structural strength. In a pipe configured without venting elements 60 and 70, the reinforcing layer 30 may be too tightly packed to allow permeated gases to readily travel down the length of the annulus. The total length of the pipe may exceed 600 m, requiring permeated gas to travel 300 m or more from the midpoint of the line to the nearest vent at a fitting. The resistance to gas flow would require high pressures in the annulus to push permeated gases through the length of the pipe. If for example, the pipe 10 was rapidly de- pressurized and/or there was a rupture in the outer sheath 50, then the resulting change in annulus pressures may be high enough to collapse the inner layer 20.

Venting elements 60 and 70 thus provide evacuation paths for gases that do permeate through layer 20. Their function is to provide a low-resistance pathway for permeated gases to travel along the length of the pipe 10, so that relatively large volumes or high flow rates of permeated gases can vent with little pressure differential along the length of pipe 10. Permeated gases may build up in the annular area between layer 20 and sheath about the fibers in layer 30 and may compromise the pipe, cause the liner to collapse or the sheath to burst. The venting elements, therefore, mitigate failures by preventing the buildup in the pipe wall of any gases that permeate through layer 20. The venting elements extend axially along the length of the pipe and open at an end of the pipe such that gases, regardless of where they permeate, can pass along the pipe through its wall and leave the pipe at its ends. The venting elements may be continuous along the longitudinal axis of the pipe and may provide a conduit to receive any gases that diffuse across the inner tubular. Trapped gases may move axially along (i.e. alongside, through or within) the venting elements ultimately to be released at an end of the pipe.

Venting elements 60, 70 can be located at any of various locations in the pipe wall, for example, in the inner tubular layer 20, within reinforcing layer 30 or between the reinforcing layer 30 and either the inner surface of the outer sheath 50 or the outer surface 24 of the inner layer. In one embodiment, venting elements 60, 70 are positioned radially outwardly of the reinforcing layer such that the reinforcing fibers can be wrapped directly onto and around the inner tubular layer 20. In particular, the elements do not interfere with substantially uniformly circumferential wraps of the reinforcing fibers. Thus, while other positions are possible, the description will proceed with emphasis on the venting elements being positioned at the interface of the reinforcing layer and the outer sheath.

Elements 60, 70 could be linear along the pipe (i.e. substantially parallel to long axis x). However, if pipe flexibility and durability is a concern, the elements may be included in the pipe wall in a helical orientation around pipe center axis x. For example, some elements may installed as helical wraps in the pipe wall around layer 30. If configured helically, the elements may have a wrap angle such as up to about 55°. However a minimal wrap angle such as less than 20°, likely from 5° to 15°, relative to the long axis allows the gas path length along the element to be minimized while achieving the benefits of helical installation. For example, when lower wrap angles are used, relatively stiff venting structures 60, 70 are prone to buckling when the pipe is bent or spooled. If a higher wrap angle is used, it increases both material usage, the cost and the total length of the venting path.

Pipe 10 includes two types of venting elements: a venting channel 60 and a non- compressible venting structure 70. Venting channels 60 may take any of various forms but at least are elongate channels extending along the length of the pipe, the channels defined between long sidewalls that are substantially smooth in the longitudinal direction. The smoothness of the surfaces may minimize friction and flow resistance. Venting structures 70 are formed of material with high lateral compressive stiffness capable of little or no lateral distortion or creep at temperatures lower than 110°C and lateral compressive pressures up to 15000 psi. Structures 70 include elongate conduits therein or are configured to maintain elongate conduits thereabout when incorporated in a pipe wall. While channels 60 and structures 70 are shown together at the interface of layer 30 and sheath 50 in the illustrated pipes, these venting elements may be at different radial depths within the pipe wall. As noted, venting channels 60 may take any of various forms but are elongate, open conduits extending along the length of the pipe. Channels 60 are configured such that they are continuous and open along their entire length which is along the length of the pipe. The channels are elongate empty spaces defined between side walls 60a that are substantially smooth in the longitudinal direction. Being substantially smooth in the longitudinal direction, for example without laterally extending surface texturing and without surface irregularities and indentations, the side walls create little resistance to the passage of the gas through the channels. The walls defining venting channels 60 may be made of various materials including polymeric materials. Generally, side walls 60a that give the best performance in terms of construction and ease of gas evacuation are of polymeric materials that are malleable at temperatures lower than 110°C.

The venting channels, for example, may be defined within longitudinally extending grooves formed in either or both of: the outer surface 24 of the inner tubular liner or the inner surface of outer sheath 50. Such grooves could be formed during construction of the layer/sheath such as during extrusion and could be linear along the layer and/or the sheath or could be oriented helically. As grooves, the polymeric walls defining therebetween the venting channels are of the material forming the layer 20 or the sheath 50. The grooves are formed such that their elongate surfaces are substantially smooth.

In the illustrated embodiments of Fig.s 2a and 2b, venting channels 60 are formed in or alongside elongate, flexible members such as polymeric rods 82 or ribbons 90 (The skilled person may sometimes commonly refer to these members as rod, string, line or the like). Sidewalls 60a, therefore, are side surfaces of the elongate, flexible members. For example, in Fig.s 2a and 3, the venting channels 60 are formed alongside rods 82. For example, in Fig.s 2b and 6, the venting channels 60 are formed alongside, such as below, ribbons 90. Flexible members 82, 90 each have longitudinally smooth side surfaces, at least on the surfaces alongside which channels 60 are formed. Members 82, 90 are flexible, malleable and light weight and may be manipulated, for example, helically wound with ease. Members 82, 90 may be formed of polymers such as for example polyethylene (PE) such as including HDPE including, for example, HDPE-RT, polypropylene (PP), PEX and nylon. In one embodiment, when members 82, 90 are positioned between layer 30 and layer 50, the elongate members may be formed of materials with similar material properties as that material from which the sheath is constructed. For example, in one embodiment, the elongate members, polymeric rods 82 for example, may comprise of a plastic with a similar melting point as the outer sheath 50. This may provide a bond between the smooth surface polymeric rods 82 and the outer sheath 50 during manufacturing of the pipe 10. Bonding can hold the polymeric rods 82 in place when the pipe is moved, bent, or manipulated during handling or installation. If polymeric rods 82 were free to move, then vent channel 60 could be compromised and venting performance negatively affected. In one embodiment, for example, both members 82, 90 and sheath are formed of polyethylene-based materials.

In the illustrated embodiments, elongate members 82, 90 are positioned on reinforcing layer 30 and may be bonded or unbonded to the surfaces of the reinforcing fibers and/or the inner surface 52 of the outer sheath. As noted, side walls 60a of channels 60 are, in this embodiment, the substantially smooth longitudinal sides of the elongate members 82, 90. The channels are defined between the members and the surface on which they are supported. As such, in this embodiment, channels 60 are further enclosed, and have side walls defined, by the outer surface of the reinforcing layer 30. In some orientations, a further side wall of at least some channels may be the inner surface of sheath 50.

Elongate members 82, 90 may be wound, at a specified winding angle, around the inner tubular layer 24 or the reinforcing layers 30. Winding angles of less than 55° may be used. In one aspect, winding angles of less than 20° or within the range of 5° and 15° may be used. While elongate members 82, 90 may be wound in the positive or negative helical direction, in one embodiment, elongate members 82, 90 are wound in the same helical direction as the final rove of fibers in the reinforcement layer 30. Having the elongate members wound in the same helical direction as the final rove of fibers in the reinforcement layer 30 minimizes cross over points and associated stress concentrations between the fibers of layer 30 and the venting elements.

There may be more than one elongate member in a pipe wall. For example, there may be a plurality of elongate members spaced apart around the circumference of the pipe. These plurality elongate members may be of the same or different types (i.e. the same or different materials, the same or different cross sectional shapes, etc.). The elongate members may extend substantially in parallel, with substantially consistent spacing and not crossing over each other. For example, if arranged as helical wraps, the plurality of elongate members each may have similar wrap angles.

Rods 82 and ribbons 90 are similar in many ways and generally differ only in their cross sectional shape. Rods 82 are substantially rounded in cross section such as having a circular or ovoid cross sectional shapes. Other shapes, e.g. star or spline, may be used but are less readily available. Different diameters of rods 82 may be used. Rods 82 may have a diameter of about 1- 4mm for a 5 inch (-12.5 cm) outer diameter (OD) pipe and may be larger or smaller but within similar ratios for other pipe diameters. Venting performance may decrease for rods with smaller diameters, as channel 60 becomes smaller. Rods 82 with a larger diameters may cause disturbance to the uniformity and thickness of the outer sheath 50 and may cause high stress concentrations on the reinforcement layer 30, specifically at the edge of pipe fittings. If one rod 82 is used to form a venting channel, the channel may be formed alongside the rod against the reinforcing layer. However, such a channel is fully open to the sheath and it can infiltrate that channel during manufacture or use. To avoid situations where the sheath infiltrates and therefore blocks the channel, the rods can be arranged to create each channel 60 between two rods, to thereby protect the. channel integrity. When rods are used, at least two rods may be employed positioned close together along their entire lengths such that the channel defined between and along the lengths of the two rods is substantially triangular in cross section with the reinforcing layer 30 forming the lower limit, third wall of the channel. For example, each channel 60 may be created between two or more rods spaced less than one rod diameter apart and possibly touching one another along their lengths, either one on top of the other or side by side. As such, venting channels 60 are formed in-between each two adjacent elongate rods 82 and against the reinforcement layer and venting channels 60 are protected from occlusion by polymer from the sheath 50, as the sheath during pipe construction and under normal use cannot pass between the two adjacent rods into channel 60.

As shown in Fig.s 2a and 3 for example, the elongate members may comprise of smooth surfaced polymeric rods 82 that are rounded, such as circular, in cross section. There may be at least two or at least three (i.e. groups of four are shown) rods 82 in a plurality of clusters wound around the pipe. The rods are in clusters, positioned side-by-side each supported on the reinforcing layer and each touching at least one other rod in the cluster. There may be at least two or more rod clusters spaced apart around the circumference of the pipe. In one embodiment there may be at least three groups around the pipe, each cluster group comprised of at least four rods. The groups may be wound in the same direction. The more rods in a cluster, the greater the combined cross sectional area of channels 60 for gas evacuation. The number of rods in a group and the number of groups is chosen based on the use of the pipe, desired performance strategies, safety considerations, and the cost.

In another embodiment, as depicted in Fig.s 2b and 6, the elongate member may be shaped as a ribbon 90 that creates one or more channels 60 along its side surfaces 60a against its supporting structure, herein layer 30. Side surfaces 60a are smooth in the longitudinal direction. As may be appreciated, ribbon 90 has the cross sectional shape similar to a cluster of rods 82, which is a plurality of rods connected side by side.

Ribbon 90 includes a plurality of venting passages 92 continuous along its length. The side surfaces 60a define the open area within and extending along the length of each passage 92. There may be at least two venting passages 92 continuous along the full length of the ribbon 90. In one embodiment, the venting passages 92 may open on the broad side at ports 91 such that passages are in fluid communication with the annulus between the inner tubular layer 20 and the outer surface 34. Passages 92 may be may be grooves, such as elongate indentations on at least one broad side surface of ribbons and ports 91 may be continuous along the length of each passage 92 such that there is no barrier to gas within the reinforcing layer 30 entering the passages and passing along them towards the end of the pipe. In the pipe, ribbon 90 has its broad side with ports 91 positioned against the reinforcing layer such that gas permeating through layer 30 can pass directly into channels 60 and the channels are protected against infiltration of sheath during manufacture or use.

There may be at least one ribbon 90 in the pipe wall. In the illustrated embodiment, three ribbons 90 are spaced apart around the circumference of pipe 10.

Referring now as well to Fig. 4, as noted, pipe 10 also includes venting structures 70, which are formed of material that is thermally stable and substantially non-laterally compressible at normal operating conditions. For example, formed of material with high lateral compressive stiffness capable of little or no lateral distortion or creep at temperatures lower than 110°C and lateral compressive pressures up to 15000 psi. Venting structures 70 form gas conduits along its length therein or thereabout when incorporated in a pipe wall.

While venting channels 60 with smooth sidewalls 60a perform very well to permit evacuation of gases therealong, in some applications channels 60 can become closed off by compression and/or thermal expansion of the elongate members 82, 90 due to compression forces and/or high temperatures along the pipe for example at an end fitting. To avoid failures due to buildup of permeated gas under these circumstances, the pipe includes venting structures 70. Each venting structure 70 extends the full length of the pipe, the same as channels 60, and structures 70 also provide a passage 40 for gas evacuation, but one that is resistant to compression and thermal expansion.

Each venting structure 70, while longitudinally flexible, possesses a high lateral compressive stiffness across its diameter, providing a consistent shape even when the pipe 10 is exposed to elevated temperatures and compressive pressures. Thus, venting structures 70 ensure that a venting conduit remains open even across a fitting. In one embodiment, venting structure 70 is a metal cord. A metal cord is, of course, a bundle of metal wires 72. While cord does not have a smooth longitudinal surfaces like sidewalls 60a of elements 82, 90, the conduit 40 for gas evacuation is the space between wires within the bundle or spaces formed between the outer surface of the cord and sheath 50 and/or reinforcing layer 30.

Pipe 10 may include one or more metal cords that are helically wound in either a clockwise or a counter clockwise direction around the reinforcing layer 30. Single metal cords can be used or they can be combined, as by twisting or braiding with other metal cords to form bundles of metal cords. The metal cords may be spaced between the elongate members (polymeric rods 60).

Metal cords of various dimensions could be used. In one example, the metal cords have a diameter of about 1.0mm to about 4.0mm (in a 5 inch OD pipe), with a wire size of about 0.2 mm to about 0.5 mm. Small or large diameters of metal cords may be used, in such cases, performance may be proportional to total cross-sectional area of the gas conduits along the pipe wall. Large cords 70 may create significant stress concentrations on the underlying reinforcing layer 30 and the stiffness of the metal cord may effect cord flexibility and thereby the pipe bending capacity. The metal can be, for example, aluminum, copper, steel, etc. including for example, alloy steel, stainless steel, etc. The metal cords may be treated, such as by galvanization with zinc, copper, etc., to make them corrosion resistant such as by corrosive permeated gases. The metal cord construction and material properties can be selected such that stress levels are low enough to prevent stress corrosion cracking in the presence of hydrogen sulfide.

The wires 72 in a useful metal cord 70 can be twisted together. The cord could have a Lang's lay configuration. In one embodiment, a useful metal cord 70 has a first layer of metal wires wound around a central guide wire in a first direction and a second layer of metal wires wound around the first layer of metal wires in the same direction. This can be referred to as a Lang's lay configuration and can result in better fatigue resistance. Because both the first layer and the second layer are wound in the same direction, the lay direction of the metal cord can be defined by the winding direction of either the first layer or the second layer.

If more than one metal cord is used, some of the metal cords can have an S lay direction and some of the metal cords can have a Z lay direction. In another aspect, all of the metal cords can have the same lay direction.

The one or more metal cords 70 can be wound in a first direction, for example either clockwise or counterclockwise. The smooth surface polymeric elongate members 82 and/or 90 can be wound also in the first direction. The metal cord(s) 70 may be wound around the reinforcing layer 30 in the same direction as, or in the direction opposite to, the reinforcing fibers of layer 30. In one embodiment the venting elements may be wound around the reinforcing layer 30, in the same direction as the reinforcing fibers of layer 30 minimizing the relative angle of the crossover points and the associated stress concentrations between the venting elements and the reinforcement fibers.

There may be more than one metal cord 70 in the pipe and all cords are placed such that it is at a sufficient distance from any elongate members 82 or 90, to avoid interfering with them or their grouping or bundling. Metal cord 70 may be placed approximately symmetrically around the pipe 10 circumference, as their stiffness in tension influences the bending characteristics of the pipe 10. For example, if all of the metal cords were on the same side of the pipe they may create a single preferred bending direction, leading to twisting or kinking of the pipe. Being circumferentially, substantially evenly spaced apart about the pipe circumference, with a symmetric pattern, the metal cords 70 do not hinder pipe performance.

In another embodiment, as depicted in Fig.s 2b and 5, another venting structure is shown in the form of an elongate, tubular member 93. As with metal cord, member 93 is longitudinally flexible (capable of bending along its length such that it can be helically wound and can bend with the pipe) but is resistant to compression even at high compressive pressures at least up to 1 10°C. One or more conduits 40 are provided along the length of member 93, and the body is formed of a porous material such that permeated gas can move from layer 30 into and along the conduits to be evacuated at the ends.

There may be at least one member 93 in the pipe wall. In the illustrated embodiment, three members 93 are spaced apart around the circumference of pipe 10.

The outer sheath 50 encloses the inner tubular layer 20, the reinforcing layers 30 and the venting elements, The outer sheath has an inner surface 52 and an outer surface 54. The outer sheath 50 holds the venting elements in place. The outer sheath may closely conform to the outside contours of the reinforcing layer and the venting elements. The material of the outer sheath 50 can be selected to primarily protect the reinforcing layers 30 from damage, such as by abrasion, and assist in stabilizing and holding the fibers of the reinforcing layers 30 in place. In one aspect, the outer sheath 50 may be made of the same plastic as the inner tubular layer 20. In one aspect, the material selection of the outer sheath 50 may be based on factors such as abrasion resistance, UV exposure, cost, degradation from environmental effects (i.e. ultraviolet light, weather, etc.), the chemicals that may come in contact with the outer sheath 50, etc. In an aspect, the outer sheath 50 can be applied by extrusion over the reinforcing layers and the venting elements in such a manner to cause the outer sheath 50 to at least partially mold over the venting elements causing the venting elements to adhere to some degree to the inside of the outer sheath.

The pipe 10 can be used to transport pressurized fluids. Where previous conventional flexible reinforced pipes may be ideally suited for transporting of pressurized fluids having an upper level temperature of around 60°C, in one aspect, the pipe 10 can transport pressurized fluids with temperatures of 60°C-120°C and mitigates and/or addresses gas permeation through liner 20. In the pipe 10, the inner tubular layer 20 does not necessarily need to provide significant structural support for the pipe 10 and may not necessarily be required to withstand the internal pressure imposed by pressurized fluid passing through the pipe 10. Rather, the inner tubular layer 20 can be used to primarily prevent the diffusion of the fluid outwardly from the inner diameter 23. The reinforcing layers 30 can act in combination with the venting elements to counteract the internal pressure imposed on the pipe 10 by pressurized fluid passing through the pipe 10 and facilitate venting of gases across the diameter of the pipe 10.

The pipe may be subjected to higher pressure or temperatures particularly where the pipe is connected to a fitting. In particular, the fittings typically connect to an end section of a pipe by using pressure to clamp down on the pipe and hold it in place to connect to the fitting. These conditions can cause thermal expansion and can cause sheath 50 and/or members 82, 90 to distort and occlude the channels 60. Venting structures 70, which are non-compressible and thermally stable, for example which have high lateral compressive stiffness capable of little or no lateral distortion or creep at temperatures lower than 110°C and lateral compressive pressures up to 15000 psi, ensure that gas evacuation conduits remain open through the fitting.

EXAMPLES

Example 1

The table below lists measured permeability coefficients for various materials and temperatures. The table illustrates that permeability can be reduced over standard HDPE performance when nucleating agents (Milliken) and selected polymer such as EVOH are added.

Methodology:

The TWI testing was conducted using coupon-level test samples cut from short sections of a pipe liner. In this simple setup, one side of the coupon is isolated from the other with a pressure tight seal, and the test coupon is heated to a known fixed temperature. Then, one side of the sample is pressurized with a known gas, such as C0 ₂ or CBU, to a known pressure, and with the samples held at fixed temperatures. Mass chromatography is used to detect the rate of gas permeation to the other side of the test coupon. Finally, using a measured mass flowrate and the wall thickness, the permeability coefficient for a given test temperature and permeating test fluid was calculated, allowing comparison of permeation rates for various inner layer polymer compositions. The two tests were conducted using a full pipe with pipe samples of 52 meters in length. One end of the pipe's annulus space was connected to a pressure transducer, and the other end of the pipe's annulus space was connected to a mass flowmeter. Using the measured mass flowrate and wall thickness of each pipe's inner layer, the permeability coefficient for a given test temperature and permeating test fluid, was calculated. The test results show that the addition of Milliken, a nucleating agent, to HDPE in the inner layer resulted in a reduced permeation rate in comparison to the standard HDPE, in the inner layer. Table 1 : Permeability of pipe

Notes:

a. CB = carbon black (a typical colourant and ultraviolet stabilizer)

PE-RT - (high density) polyethylene - raised temperature; our standard HDPE for our 82°C rated product

Milliken = Ravago Crystaladd™, grade HM-237 NAT™ nucleating agent

b. Permeability coefficient indicates how readily the material allows the gas in question to permeate. It is a normalized coefficient used to compare different materials independent of thickness, size, and gas pressure; a permeation flow rate for a given pipe can be calculated by multiplying this coefficient by pressure differential and surface area, and dividing by material thickness. Lower numbers are desirable for blocking permeation; for C02, EVOH has permeability an order of magnitude lower than all the other materials listed.

c. TWI = measured for Shawcor by TWI, a test lab in the UK

CPS = Composite Production Systems, i.e. tested by Shawcor in-house

Example 2

The two tables below are a direct comparison of non-nucleated and nucleated liners in a substantially similar test environment. They key performance indicators are front end annulus pressure and annulus flow. For the nucleated liner, at all bore pressures, the front end annulus pressure is lower than for the non-nucleated liner, and at the three highest bore pressures the annulus flow is also lower, demonstrating mitigation of the risk of the liner collapsing or the sheath bursting.

Methodology:

In both cases a pipe of 52 meters in length was pressurized in the bore with a gas of known composition, such as C0 ₂ , known normalized permeation rates through for HDPE-RT, and at a known pressure and temperatures. One end of the pipe's annulus space was connected to a pressure transducer, and the other end of the pipe's annulus space was connected to a mass flowmeter. The individual rows in each table are experimental data corresponding to the resulting annulus pressure and rate of permeated volume of gas in SCCM (standard cubic centimeters per minute) under steady-state conditions, for the known pipe length, pipe temperature, bore pressure and bore fluid.

Table 2: Permeation comparison of non-nucleated and nucleated HDPE liners; the permeation test done on control pipe is 3"FP601HT pipe (no nucleating agent and no venting elements).

Example 3

Venting elements 60 and 70 are provided to provide evacuation paths for gases that may permeate through the inner layer 20. Permeated gases may build up in the annular area between the inner layer 20 and the outer sheath 50 about the fibers in reinforcing layer 30 and may cause the inner layer 20 to collapse or the outer sheath 50 to burst. The venting elements, mitigate failures by preventing the buildup of any gases that permeate through layer 20. The preferred embodiment is highlighted (and was selected) because the front end annulus pressure is drastically reduced relative to the other variants for at a given bore pressure, temperature, and pipe sample length, and therefore significantly mitigates the risk of the liner collapsing or the sheath bursting. The key performance indicators are front end annulus pressure, and annulus flow. Table 3 : The below table is a venting performance comparison between a baseline (row 1 ) and different vent channels types and arrangements. All variants have the same nucleating agent, despite rows 3 and 4 not referencing it,

Example 4

The graphs illustrate the theoretical effect of an inner tubular layer that is coextruded see Figs. 7 and 9, with different materials 22 of varying thickness, on annulus 15 pressure in modelled pipe 10 for an inner tubular layer 20 of practical and constant overall inner diameter D. The data demonstrates that for increasing co-extruded inner layer thicknesses in inches of PA, PVDF, and EVOH, there is a resulting reduction in permeated volume measured in SCCM relative to the standard HDPE control sample. It also highlights the enhanced performance of the EVOH layer, due to the reduction in permeated volume.

Fig. 7 illustrates annulus pressure and permeation (modeled, assuming no venting) of various polymeric liners, based on permeation coefficients of each material. Table 4: Permeation rate comparison of co-extruded PA, PVDF, EVOH relative to standard HDPE liner. The following table is a numeric tabular representation of Annulus Flow graphical data shown in Fig.7.

Example 5

The venting performance of the present pipe is impacted by inclusion of both non-compressible steel cord and channels formed by smooth polymer venting elements, also referred to the graph in Fig 8 as the poly cord venting elements, along the full pipe length of the pipe. Figure 8 shows comparisons of measured venting performance for prototype variants. While all prototype variants show venting performance with orders of magnitude improvement over the baseline product, the combined steel and poly cord design, shown in Fig. 8 exhibits superior performance compared to steel cord or poly cord venting elements alone. Note that due to the log-log scale, differences are much more dramatic than they appear; i.e. the top line is >300x higher flow rate than the bottom line. Note that the slope of the "steel cord only" line compared to the others, shows that venting performance decreases faster with increasing pipe length. Methodology:

The data in Fig, 8 is based on a test, in which air at a controlled pressure is injected directly into the annulus at one end of a length of pipe, and the volumetric flow rate of air through the length of the annulus is measured (essentially a measure of total resistance to flow - longer lengths or less freely-flowing designs will carry a lower flow rate for a given inlet pressure). These tests are done at room temperature, so that there is no significant 'choking' effect of the poly cords expanding at high temperature and closing off the venting paths.

The "steel cord only" pipe when compared to the pipe of Fig. 2a, has an inner tubular layer like 20. However, instead of reinforcing layer 30, there are two counterwound layers of steel cord (as opposed to glass fiber), primarily for cyclic load capability. There are no polymeric elongate members and no channels 60. There is an outer sheath, similar to 50. The main difference is there is an intermediate polymer layer separating the counterwound layers of steel cord. Substantially, all gas that permeates through layer 20 must travel alongside the "inner" steel reinforcement layer.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to those embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the full scope consistent with the claims, wherein reference to an element in the singular, such as by use of the article "a" or "an" is not intended to mean "one and only one" unless specifically so stated, but rather "one or more". All structural and functional equivalents to the elements of the various embodiments described throughout the disclosure that are laiown or later come to be known to those of ordinary skill in the art are intended to be encompassed by the elements of the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 USC 1 12, sixth paragraph, unless the element is expressly recited using the phrase "means for" or "step for".