LISTER, John David (2 York Road, London SE1 7NA, GB)
VAN BEEK, Johannes, Carolus, Catharina (Kessler Park 1, GX Rijswijk, NL-2288, NL)
DAM, Willem (Carel van Bylandtlaan 23, HR The Hague, NL-2596, NL)
PERSAUD, Michael, Alan (Level 21, Tower 1 ETIQA Twins, N0. 1, Jalan Pinang Kuala Lumpur, 50450, MY)
BURNS, Rober Arthur (Poole Lane, Ince, Chester Cheshire CH2 4NU, GB)
LISTER, John David (2 York Road, London SE1 7NA, GB)
VAN BEEK, Johannes, Carolus, Catharina (Kessler Park 1, GX Rijswijk, NL-2288, NL)
DAM, Willem (Carel van Bylandtlaan 23, HR The Hague, NL-2596, NL)
PERSAUD, Michael, Alan (Level 21, Tower 1 ETIQA Twins, N0. 1, Jalan Pinang Kuala Lumpur, 50450, MY)
| C L A I M S 1. A vessel (1) for the processing of a hydrocarbon stream, the vessel having a hull (2) comprising longitudinal sides (4, 6), a deck (8) being located atop the hull and between the longitudinal sides, a longitudinal mid-plane (10) in between the longitudinal sides, and a pipe arrangement (12) which includes a plurality of pipes (14), wherein the plurality of pipes in the pipe arrangement are configured into a plurality of first sub-arrangements (16) and each first sub-arrangement comprises at least one pipe, wherein the first sub-arrangements (16) are spaced apart from one another and arranged on the deck (8) outwardly of the longitudinal mid-plane (10) of the vessel, wherein at least one first sub-arrangement (16) is arranged on one side of the longitudinal mid-plane and at least one other first sub-arrangement is arranged on the opposite side of the longitudinal mid-plane. 2. The vessel according to claim 1, wherein the pipe arrangement spans the beam of the vessel across the deck (8) . 3. The vessel according to claim 1 or 2, wherein the plurality of pipes in the pipe arrangement are evenly distributed over the beam of the vessel across the deck (8) . 4. The vessel according to claim 2 or 3, wherein the plurality of pipes in the pipe arrangement are spread out over more than 50% of the beam of the vessel. 5. The vessel according to claim 2 or 3, wherein the plurality of pipes in the pipe arrangement are spread out over more than 75% of the beam of the vessel. 6. The vessel according to claim 2 or 3, wherein the plurality of pipes in the pipe arrangement are spread out over more substantially the beam of the vessel. 7. The vessel of any of the preceding claims, wherein the pipe arrangement (12) further comprises at least one second sub-arrangement (18), each second sub-arrangement comprising at least one pipe, arranged proximate to and/or at the longitudinal mid-plane (10) of the vessel (1) . 8. The vessel according to claim 7, wherein at least one second sub-arrangement comprises pipes carrying at least a part of the hydrocarbon stream. 9. The vessel according to claim 7, wherein at least one second sub-arrangement comprises pipes carrying cryogenic material . 10. The vessel according to claim 6, wherein the cryogenic material is liquefied natural gas. 11. The vessel according to any of the preceding claims, wherein the pipes (14) of the pipe arrangement (12) are at least partially elevated with respect to the deck (8) to provide a passage perpendicular to the mid-plane (10), the passage having a height (Li) that is sufficient to provide a passageway for people. 12. The vessel according to any of the preceding claims, further comprising at least one processing deck (20), which is elevated with respect to the deck (8), the processing deck having processing units (22) for the processing of the hydrocarbon stream located thereon, wherein the pipe arrangement (12) is located between the deck (8) and the processing deck (20) . 13. The vessel according to claim 12, wherein the vessel comprises a maintenance deck (24) located between the deck (8) and the processing deck (20) . 14. The vessel according to any of claims 10-13, wherein the pipes of the pipe arrangement (12) are attached to the underside of the maintenance deck. 15. The vessel according to any of claims 9-14, wherein safety gaps (54) are arranged between adjacent processing units . 16. The vessel according to claim 15, wherein each processing unit is arranged on a separate processing deck, and wherein adjacent processing decks carrying their respective processing units are separated by corridors (26) and safety gaps (54) . 17. A vessel according to any of the preceding claims, wherein the pipe arrangement (12) has no more than three pipes in vertical alignment with one another. 18. A vessel according to any of the previous claims, the vessel comprising an offloading system (30) which is located on an offloading side of the vessel, wherein one of the first sub-arrangements (16) located outermost of the deck (8) relative to the longitudinal mid- plane (10) of the vessel and closest to the offloading side comprises pipes that are non-hazardous material carrying pipes. 19. A vessel according to claim 18, wherein one of the first sub-arrangements (16) located outermost of the deck (8) relative to the longitudinal mid-plane (10) of the vessel and farthest away from the offloading side comprises pipes that are hazardous material carrying pipes. 20. A vessel according to claim 18, wherein non- hazardous material carrying pipes are included in first sub- arrangements on the off-loading side of the vessel, and wherein all hazardous material carrying pipes are included in first sub-arrangements (16) located outermost of the deck (8) relative to the longitudinal mid-plane (10) of the vessel and farthest away from the offloading side. 21. The vessel according to claim 18, wherein pipes carrying the most dangerous streams, such as high pressure and/or high temperature steam, are (all) located on the side of the vessel opposite to the offloading side, and are segregated from pipes carrying hydrocarbons. 22. A method for the liquefaction of a gaseous hydrocarbon stream to at least provide liquefied natural gas (LNG) , using a vessel according to any of the preceding claims. |
The present invention relates to a vessel for the processing of a hydrocarbon stream, the vessel having a hull comprising longitudinal sides, a deck being located atop the hull and between the longitudinal sides, a longitudinal mid- plane in between the longitudinal sides, and a pipe
arrangement which includes a plurality of pipes.
The vessel of the invention is for instance a floating liquefied natural gas carrier (LNGC) , a floating liquefied petroleum gas carrier (LPGC) , a floating liquefied natural gas production, storage and offloading structure (FPSO) , a floating liquefied petroleum gas production, storage and offloading structure, a floating natural gas treatment, liquefaction, storage and offloading (FLNG) structure, or an offshore hydrocarbon processing structure in general.
Figure 1 shows a typical FPSO structure, comprising a vessel 1 having a hull 2 comprising longitudinal sides 4, 6, and a deck 8 being located atop the hull and between the longitudinal sides. Longitudinal mid-plane 10 of the vessel is indicated in between the longitudinal sides. A pipe arrangement 11 includes a plurality of pipes 13. The pipes 13 carry for instance liquid and/or gaseous hydrocarbon feed streams, processed hydrocarbons, steam, water, electricity and/or communication lines, etc. The pipes are arranged close to each other on a structure which is called a pipe rack. The pipe rack typically has a width dl which is much smaller than the beam d2 of the vessel, wherein the beam of the vessel is its width at the widest point. The average width d2 is for instance less than 25% of dl . The pipe rack is provided as a central alley on, or above, the deck of the vessel. This pipe arrangement has been found to be satisfactory because the topside of the deck is kept relatively clear of pipes and the pipe arrangement being located in a pipe rack makes for ease of handling and construction.
A drawback of a pipe arrangement contained within a pipe rack is that the rack itself creates a track for a blast should any liquid or gaseous hydrocarbons leak from any of the pipes contained within the rack.
Previous attempts to mitigate the risks of a blast tracking along a pipe rack have involved the local broadening of the pipe arrangement at respective intervals 15 to direct a blast outboard of the vessel.
EP-2088075-A1 discloses a piping structure for an oil tanker. The piping structure comprises two longitudinal pipe racks which are arranged below the deck and on opposite sides of the mid-plane of the tanker. A third pipe rack may be located on the mid-plane. Each pipe rack includes oil
delivery pipes. An inert gas pipe 58 may be included in the pipe rack on the port side of the vessel.
It is an aim of the present invention to obviate the above mentioned drawbacks of a pipe rack and to improve the safety of the vessel.
Accordingly, the present invention provides a vessel as described above, wherein the plurality of pipes in the pipe arrangement are configured into a plurality of first sub- arrangements and each first sub-arrangement comprises at least one pipe, wherein the first sub-arrangements are spaced apart from one another and arranged on the deck outwardly of the longitudinal mid-plane of the vessel, wherein at least one first sub-arrangement is arranged on one side of the longitudinal mid-plane and at least one other first sub- arrangement is arranged on the opposite side of the
longitudinal mid-plane. The power of a blast in any of the pipes is thus mitigated, as the sub-arrangements are spaced apart from each other. Instead of a central piperack the pipes are
distributed across the width of the vessel. In case of a blast, the energy can propagate freely and is neither
channeled along the pipe rack nor obstructed by it. The pipe arrangement of the invention may extend along a substantial part of the length of the vessel. Herein, a substantial part may be at least 50% of the length from bow to stern, for instance about 60% to 90%.
In an embodiment, the pipe arrangement spans the beam of the vessel across the deck and/or the sub-arrangements are evenly distributed over the beam of the vessel across the deck, to optimize the blast mitigating effect of the spaces between respective sub-arrangements and/or pipes.
Evenly distributed herein indicates that the pipes, as seen in the length direction of the vessel, cover more than 50% of the beam of the vessel. In a preferred embodiment, the pipes of respective sub-arramgements are spread out to cover more than 75% of the beam of the vessel. Spreading out the pipes over the beam of the vessel improves air circulation between the pipes and limits the risk of blast propagation.
In another embodiment of the invention, the pipe
arrangement further comprises at least one second sub- arrangement, each second sub-arrangement comprising at least one pipe, arranged proximate to and/or at the longitudinal mid-plane of the vessel. The pipes of the second sub- arrangement are arranged close to all processing units, and are easily accessible for maintenance and check-up. The second sub-arrangement comprises pipes carrying for instance at least part of the hydrocarbon stream and/or cryogenic material, wherein the cryogenic material may be liquefied natural gas . According to a preferred embodiment, the pipes of the pipe arrangement are at least partially elevated with respect to the deck to provide a passage perpendicular to the mid- plane, the passage having a height that is sufficient to provide a passageway for people. Staff of the vessel can thus freely move across the deck, combining the advantage of blast mitigation with a cleared deck.
The vessel may comprise at least one processing deck, which is elevated with respect to the deck, the processing deck having processing units for the processing of the hydrocarbon stream located thereon, wherein the pipe
arrangement is located between the deck and the processing deck. This preferred embodiment simplifies maintenance and regular check-up of the processing units and piping, and is therefore cost effective. Also, any space within the hull and below deck is available, for instance for storage of
processed hydrocarbons.
In a further embodiment the vessel comprises a
maintenance deck located between the deck and the processing deck. Preferably, a space between the maintenance deck and the processing deck is sufficient to provide a passageway for people. The maintenance deck may extend along at least part of the length of the vessel. The maintenance deck is elevated with respect to the deck of the vessel. A corridor is
arranged in between bordering process units, the corridor having a width that is sufficient to provide a passageway for people. The maintenance deck extends along at least part of the length of the vessel. The pipes of the pipe arrangement are preferably attached to the underside of the maintenance deck. In an embodiment the maintenance deck provides passages for personnel between the deck and the maintenance deck and/or between the process deck and the maintenance deck. The maintenance deck is attached to the deck and
increases the bending and torsion strength of the deck. Staff can access and service the process units that are arranged above the maintenance deck via the passageways, whereas the maintenance deck itself protects the pipes from objects that may fall during maintenance and servicing. The space that would have previously been occupied by a pipe rack is now available for maintenance and materials handling corridor between process modules. A dedicated process module support structure is obviated because there is no preferential propagation direction of a blast.
In an embodiment the pipe arrangement has no more than three pipes in vertical alignment with one another.
In a further embodiment the vessel comprises an
offloading system which is located on an offloading side of the vessel, wherein one of the first sub-arrangements located outermost of the deck relative to the longitudinal mid-plane of the vessel and closest to the offloading side comprises pipes that are non-hazardous material carrying pipes. One of the other first sub-arrangements located outermost of the deck relative to the longitudinal mid-plane of the vessel and farthest away from the offloading side comprises pipes that are hazardous material carrying pipes. Pipes carrying the most dangerous streams, such as high pressure and/or high temperature steam, are (all) located on the side of the barge opposite to the side that has been arranged for mooring and offloading and are segregated from the pipes carrying
hydrocarbon vapour and liquid. The less dangerous utility pipes are distributed over the deck to limit congestion and to allow air movement between the pipes. Walkway space is arranged below the pipes to enable staff to move between the port and starboard sides of the vessel. Herein, pipes carrying hazardous material being
segregated from the pipes carrying hydrocarbons implies that the respective pipes are included in different sub- arrangements. Preferably, the respective pipes are arranged at a maximized mutual distance. Said mutual distance is for instance at least 25% of the beam of the vessel. The mutual distance increases air flow between the pipes, which will carry escaping hazardous materials along.
The vessel of the invention may be a floating liquefied natural gas carrier (LNGC) , a floating liquefied petroleum gas carrier (LPGC) , a floating liquefied natural gas
production, storage and offloading structure (FPSO) , a floating liquefied petroleum gas production, storage and offloading structure, a floating natural gas treatment, liquefaction, storage and offloading (FLNG) structure, or an offshore hydrocarbon processing structure.
Accoding to another aspect, the invention provides a method for the liquefaction of a gaseous hydrocarbon stream to at least provide liquefied natural gas (LNG) , using the vessel as disclosed above.
Further advantages and details of the present invention will become apparent with the benefit of the following detailed description of embodiments and upon reference to the accompanying drawings, in which:
Figure 1 shows a vessel of the prior art in perspective view, the vessel comprising a conventional pipe rack;
Figure 2 shows a transverse cross-sectional view of a vessel, looking towards the bow of the vessel, according to an embodiment of the invention;
Figure 3 shows a side cross-sectional view of the vessel of Figure 2;
Figure 4 shows a transverse cross-sectional view of an embodiment of a pipe arrangement for a vessel according to the invention and looking forward towards the bow of the vessel ;
Figure 5 shows yet a transverse cross-sectional view of another embodiment of a pipe arrangement for a vessel
according to the invention and looking forward towards the bow of the vessel; and
Figure 6 shows a perspective view of another embodiment of a vessel according to the invention.
While the invention is susceptible to various
modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood that the drawings and detailed description thereto are not
intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the scope of the invention as defined by the appended claims.
Further, although the invention will be described in terms of specific embodiments, it will be understood that various elements of the specific embodiments of the invention will be applicable to all embodiments disclosed herein.
Figure 1 depicts a vessel according to the prior art. The vessel 1 has a hull 2 having longitudinal sides 4, 6, a deck 8 and a longitudinal mid-plane 10. A conventional pipe rack arrangement 11 is located on the deck 8 and runs
longitudinally of the vessel, parallel to the longitudinal sides 4, 6.
The conventional pipe rack arrangement 11 places all pipes 13 in one location and stacks those pipes in a tightly packed configuration. Tightly packed herein implies for instance that the average width dl of the pipe rack 11 is about 25% of the width d2 of the vessel or less, for instance about 20% to 15%. The pipe rack is located on one side of the mid-plane 10, for instance near the starboard side of the vessel. The benefits of such an arrangement are that the entire pipe rack arrangement may be lifted onto the vessel 1 as a single unit and the topside of the vessel is relatively clear of pipework. The pipe arrangement is relatively easy to construct and locate.
The conventional pipe arrangement is, however, an explosion hazard in itself as a leakage of material from one of the pipes within the arrangement may form an explosion hazard. Any blast occurring at any point on the pipe
arrangement 11 will then be funneled down the pipe rack, effectively intensifying and directing the explosion hazard.
In accordance with the invention and as depicted in Figures 2 and 3, there is provided a vessel 1 for the
processing of a hydrocarbon stream. The vessel comprises a hull 2 comprising longitudinal sides 4, 6, a deck 8 being located atop the hull and between the longitudinal sides, and a longitudinal mid-plane 10 in between the longitudinal sides. The vessel is provided with a pipe arrangement 12 which includes a plurality of pipes 14, which are configured into a plurality of first sub-arrangements 16. Each first sub-arrangement may comprise one or more pipes. The first sub-arrangements 16 are spaced apart from one another and arranged on the deck 8 outwardly of the longitudinal mid- plane 10 of the vessel, wherein one or more first sub- arrangements 16 are arranged on one side of the longitudinal mid-plane and one or more other first sub-arrangements are arranged on the opposite side of the longitudinal mid-plane 10. The pipes of each sub-arrangement may also be spaced apart, so that in effect all pipes are distributed over the beam of the vessel 1. Preferably, the first sub-arrangements 16 are evenly distributed over the beam of the vessel across the deck 8. The pipe arrangement 12 may further comprise one or more second sub-arrangements 18, wherein each second sub- arrangement comprises one or more pipes. The one or more second sub-arrangements 18 are arranged near or at the longitudinal mid-plane 10 of the vessel 1. The second sub- arrangements may comprise pipes carrying liquid or gaseous hydrocarbons or cryogenic material. Cryogenic material may include liquefied natural gas and/or refrigerants such as propane .
The pipes 14 of the pipe arrangement 12 are along at least at part of the length of the vessel elevated with respect to the deck 8 to enable staff to pass from one side of the vessel to the opposite side, i.e. perpendicular to the mid-plane 10. The distance LI between the pipes and the deck is sufficient to provide a passageway for staff. LI is therefore preferably more than about 2 m.
The vessel may comprise one or more processing decks 20, which are elevated with respect to the deck 8 and have processing units 22 for the processing of the hydrocarbon stream located thereon. The pipe arrangement 12 is arranged between the deck 8 and the processing deck. The processing deck 20 may be one deck, as shown in Figure 2. Alternatively, two or more processing decks may be arranged adjacent to each other, each carrying separate processing units and having a space between bordering processing decks. The one or more processing decks 20 extend parallel to the deck 8 along a substantial part of the length and width of the vessel.
Herein, substantial part implies 80% or more, for instance about 90% to 95%. Thus the deck space of deck 8 can be cleared for passage of staff, whereas the available deck space is increased.
In addition, the vessel may comprise a maintenance deck 24 located between and extending parallel to the deck 8 and the processing deck 20. A distance L2 between the maintenance deck 24 and the processing deck 20 is sufficient to provide a passageway for people. The distance L2 is preferably more than 1.5m, for instance about 2m. A corridor 26 is arranged in between bordering process units 22, the corridor having a width L3 that is sufficient to provide a passageway for people. L3 may be more than 0.5m. The maintenance deck 9 extends along a substantial part of the process deck, and preferably about the entire process deck.
The process deck 20 or the maintenance deck 24 is connected to the deck 8 by a plurality of support structures 28 that extend along a substantial part of the maintenance deck. The process deck and the maintenance deck itself may at least partly be constructed as framework. Together with the support structures 28, the process deck and the maintenance deck thus improve the structural rigidity or strength of the deck 8. Preferably, the pipes 14 of the pipe arrangement 12 are attached to the underside of the maintenance deck 24.
The vessel comprises one or more offloading systems 30, which are located on an offloading side of the vessel.
Preferably, one or more of the first sub-arrangements 16 which are located closest to the offloading side comprise pipes that carry non-hazardous material. On the other hand, one or more of the first sub-arrangements 16 which are located outermost of the deck 8 relative to the longitudinal mid-plane 10 and farthest away from the offloading side comprise pipes that carry hazardous material. Herein, hazardous and non-hazardous are elucidated below.
A specific embodiment of the pipe arrangement 12 will now be described with reference to Figures 4 and 5 which depict partial transverse cross-sectional representations of embodiments of the pipe arrangement in accordance with the invention. Each partial transverse cross section may be taken at different locations along the length of the vessel looking forward towards the bow. The pipe arrangement 12 depicted in each of Figures 4 and 5 may relate therefore to a pipe arrangement on a single vessel and in accordance with the present invention.
The pipes in the pipe arrangement 12 are configured into a plurality of sub-arrangements and each sub-arrangement comprises at least one pipe. The specific groups or sub- arrangements are separated from one another across the width of the vessel 1 in order to reduce the danger of ignition and escalation of a blast hazard. The sub-arrangements of pipes within the pipe arrangement 12 for instance include:
utilities (excluding high pressure steam lines), high
pressure steam lines, high pressure process gas lines, cryogenic lines, flare lines and steam condensate lines.
Referring to Figure 4 and beginning with the pipes closest to the port side of the vessel (left in Figure 4), the pipe arrangement may be configured from the first pipe to the last pipe as follows:
High pressure steam line 100, seawater deck wash main line 101, fire water main line 102, cooling lines 103a, 103b, 103c, 103d, service water line 104, instrument air line 105, tool air line 106, topsides drain 107, topsides overflow 108, vapour main 109, LNG vapour line 110, inert gas main line 111, inerting line 112, condensate export main 113, vapour recovery export main 114, hot gas header/LNG/LPG/ Condensed TKS 115, fire line 116, LNG gas header 117, condensate run down line 118, LNG line 119, Slops to cleaning line 120, hydraulic return line 121, hydraulic pressure line 122, MEG sludge line 123, nitrogen supply line 124, MEG rich line 125, MEG lean line 126, steam condensate return line 127, low pressure steam line 128, fire main 129, washing main 130, cooling lines 131a, 131b, 131c and 131d. Figure 5 shows a pipe arrangement at a second and different location along the length of the hull to that shown in Figure 4. The partial cross-section of the vessel is taken transversely of the hull looking forward towards the bow of the vessel. Beginning with the pipes closest to the port side of the vessel, the pipe arrangement is configured from the first line to the last line as follows:
Seawater deck wash main 101, fire water main line 102, slop export line 140, service water line 104, instrument air line 105, tool air line 106, topsides drain 107, topsides overflow 108, condensate feed water 141, fuel gas line 142, inert gas main line 111, inerting line 112, condensate export main 113, vapour recovery export main 114, fire line 116, LNG gas header 117, hydraulic return line 121, hydraulic pressure line 122, nitrogen supply line 124, steam condensate return line 127, low pressure steam line 128, fire main 129, washing main 130, cooling lines 131a, 131b, 131c and 131d.
In a still alternative embodiment of the pipe
arrangement, the pipe arrangement could be configured from the first line to the last line as follows:
High pressure steam line 100, seawater deck wash main line 101, fire water main line 102, cooling lines 103a, 103b, 103c, 103d, service water line 104, instrument air line 105, tool air line 106, topsides drain 107, topsides overflow 108, vapour main 109, LNG vapour line 110, inert gas main line 111, inerting line 112, condensate export main 113, vapour recovery export main 114, hot gas header/LNG/LPG/ Condensed TKS 115, fire line 116, LNG gas header 117, condensate run down line 118, LNG line 119, Slops to cleaning line 120, hydraulic return line 121, hydraulic pressure line 122, MEG sludge line 123, nitrogen supply line 124, MEG rich line 125, MEG lean line 126, steam condensate return line 127, low pressure steam line 128, fire main 129, washing main 130, cooling lines 131b and 131c and produced water line 150.
Figure 4 also depicts a plurality of first sub- arrangements 16 of pipes, with each sub-arrangement
comprising at least one pipe. For example, produced water line 150 is a sub-arrangement 16 within the pipe arrangement 12. Furthermore, high pressure steam line 100, seawater deck wash line 101 and fire water main line 102 make up a further sub-arrangement 16 of pipes within the pipe arrangement 12. Further depicted sub-arrangements 16 include: service water line 104, instrument air line 105 and tool air line 106, for example .
As depicted in each of Figures 4 and 5, the pipe
arrangement 12 comprises a plurality of pipes arranged proximate to or at the longitudinal mid-plane 10 of the vessel in a second sub-arrangement 18.
It is preferred that the plurality of pipes arranged proximate to and/or at the longitudinal mid-plane 10 include a second sub-arrangement 18 of cryogenic material carrying pipes. The sub-arrangements of cryogenic lines are preferably located below the maintenance deck 24 and above the deck 8 of the vessel. In an embodiment, part or all of the non- cryogenic lines are located at remote from and/or at a higher level than the cryogenic lines, to protect the non-cryogenic lines from being affected by the cryogenic lines, i.e. from so-called cold splash effects.
In preferred embodiments, the cryogenic pipes are located within the central 10 m of the width of the deck, proximate to the mid-plane 10 of the vessel.
The high pressure steam line 100 is preferably located towards the port side of the vessel in order to reduce the risks associated with leakage of high pressure steam on the mooring side of the vessel. Low hazard pipework is preferably located outboard of the mid-plane 10 of the vessel on the starboard side thereof as the lowest risk pipes are then located on the side of the vessel adjacent the mooring side and loading arms 30.
Figure 6 shows vessel 1 for, for instance, the
treatment, liquefaction, storage and off-loading of natural gas (FLNG) . Near the bow thereof, vessel 1 has a turret 50, which is connected via risers to subsea hydrocarbon
reservoirs. The vessel can swivel around the turret, which is anchored to the seabed. Liquefied natural gas carrier (LNGC) 52 is moored at the mooring side of the vessel 1, in parallel to longitudinal side 6, and is coupled to off-loading
structure 30.
The vessel 1 of Figure 6 is provided with a plurality of processing units 22. The vessel is provided with a pipe arrangement 12 arranged between the deck 8 and the processing units, for instance as shown in any of Figures 2 to 5. Along the length of the vessel, explosion safety gaps 54 are provided between bordering processing units for explosion and fire escalation mitigation. The explosion safety gaps have a minimum width L4 of, for instance, 20 m or more. The pipe arrangement 12 of the present invention allows the use of safety gaps 54, as in order to be effective these gaps need to be free of congestion to allow any explosions to decay across the gap and to direct a blast to the sides of the vessel. Having a large congested piperack running between modules would effectively couple the modules, thereby
severely reducing the effectiveness of the gaps.
Computer modelling has shown an advantage in locating the piping in a pipe arrangement according to the present invention compared to piperacks located above the deck centrally or on the port side of the vessel. This advantage is due to the impact that the piperack options have in restricting air flow within the safety gaps leading to larger flammable cloud sizes. By arranging sub-arrangements of pipes in certain areas on the deck 8, greater airflow is ensured thereby reducing the blast potential and vapour build up potential in the pipe arrangement.
A blast will accelerate through constrictions caused by congested pipework within a pipe arrangement due to a Venturi effect accelerating the flow of vapour and gas of the blast. A pipe rack of the prior art inherently provides a congested zone wherein the blast potential is enhanced by the
configuration of the pipes within the pipe rack. By reducing pipe congestion, a pipe arrangement of the present invention reduces the potential of a blast and/or blast acceleration.
In embodiments of the invention wherein a vessel is provided having both separate modules with gaps therebetween and a pipe arrangement according to the invention, the benefits of spaced modules in directing any blast or vapour build up outboard of the mid-plane 10 of the vessel are maintained whilst, at the same time the pipe arrangement of the invention reduces the likelihood of a blast occurring or being focused or accelerated by reducing congestion of the pipes within the pipe arrangement. Thus, a dual blast hazard reduction is provided by having gaps between modules and a pipe arrangement of the invention.
In preferred embodiments, the pipe arrangement has no more than three pipes in vertical alignment with one another. Where possible, all piping has a minimum of 2 m of clear space between the bottom of the lagged pipe and the deck 8 so as not to hinder access and egress.
Suitably there is straight and unhindered access on the port and starboard side of the deck 8 forming escape routes for evacuation of the vessel. There may be a deviation from this straight escape route on the starboard side of the vessel to clear the loading arms.
Referring to Figure 2, the vessel will typically have a processing deck 20 having processing units 22 located
thereon. Certain pipes, such as flare header and the main inter module high pressure process gas lines, may be located above the process deck level.
Preferably, and with exceptions (such as flare lines and high pressure inter module process gas lines), no piping crosses the areas between modules located at the starboard or portside of the vessel, in order to preserve the presence of inter module gaps. Said gaps reduce the potential explosion overpressures which may arise in these areas. Furthermore, these gaps may be used as lifting corridors, for example.
Where possible, and within the constraints of space and the number of hull penetrations required, as many non- hazardous material carrying lines or pipes as possible may be located within the hull.
The central, port and starboard corridors of the vessel as well as the inter-deck areas may be used as conduits for piping, cabling and HVAC ducting. Non-hazardous material carrying pipes may be located inside the hull of the vessel. Herein, non-hazardous material excludes hydrocarbon, toxic, or asphyxiant material, or high pressure steam.
In exemplary embodiments of the present invention, the following lines or pipes are suitable for location within the hull of the vessel: tool air lines, fire water lines, cooling water lines, chilled cooling water lines, steam condensate return lines, cabling, HVAC ducts, glycol heating medium lines.
Further precautions and safety procedures may need to be established and adhered to when locating certain lines or pipes within the hull. Safety precautions made be required to address risks of leakage, condensation and access restrictions. Certain types of lines or pipes are segregated from one another. For instance, water service lines are kept remote from or at a lower level than electrical cabling.
The integrity of a deck of a vessel is critical to the protection of the cryogenic tanks within the vessel and must not be impaired by use of the hull of the vessel for piping and cabling. All deck penetrations should be configured to withstand projectile, overpressure, cryogenic and fire events such that the deck penetration is not to be weaker than the original deck. Furthermore, all deck penetrations should be gas and liquid tight. Grouping deck penetrations together, for example one per module area, helps to minimize congestion as well as allowing common shielding to be used.
As will be understood upon reading the present
disclosure, the vessel of the invention may be a floating liquefied natural gas carrier, a floating liquefied petroleum gas carrier, a floating liquefied natural gas production, storage and offloading structure, a floating liquefied petroleum gas production, storage and offloading structure or an offshore hydrocarbon processing structure.
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