JP2010526256A - Unloading pipeline - Google Patents

Abstract

A system for transporting cryogenic fluid comprising a carrier pipe (2) and at least one inner product flow pipe (1) disposed in the carrier pipe (2) and insulated from the carrier pipe, The product pipe (1) is more than the carrier pipe (2) so that the thermal contraction of the product pipe (1) due to the temperature change of the product pipe (1) is accepted by the elastic geometric distortion of the product pipe (1). A system that has a long length and is incorporated within the entire length of the carrier pipe (2) by following a non-linear path.
[Selection] Figure 1

Description

  The present invention relates to a pipeline system for transferring cryogenic fluids such as liquefied natural gas (LNG). In particular, it relates to a pipeline system for transporting fluid along the sea floor between an offshore terminal and a coastal facility.

  In places where large amounts of natural gas are produced, the common technology for transporting gas to distant markets is to liquefy the gas at a coastal location near the gas source and then install it on the ocean vessel Transporting liquefied natural gas (LNG) in a specially designed storage tank. To form LNG, natural gas is compressed and cooled to cryogenic temperature, ie -160 ° C, increasing the amount that can be carried in the storage tank. When the ocean vessel arrives at its destination, the LNG can be unloaded into an onshore storage tank, then LNG can be re-vaporized from this tank as needed and transported to the end user through a pipeline or the like. it can. By providing a gap under the keel of a large LNG tanker when the seabed gently forms shallow water from the coast, and by positioning the loading / unloading facility sufficiently away from the coastal environment, health, safety and If it is necessary to obtain environmental benefits, it is desirable to place an LNG import or loading terminal far from offshore.

  Currently known cryogenic fluid transfer systems include systems installed on a causeway or trestle jetty specially constructed between a coastal tank and an offshore receiving / loading facility. Supporting such a long bank or jetty LNG loading line is expensive. The trestle needs to be high enough from the surface of the water so that the transfer line is not submerged and in some cases does not interfere with existing maritime traffic. Due to construction costs, offshore facilities should be installed near the coast. For this reason, in order to ensure the safety of the passage for the deep draft LNG transport ship, it may be necessary to construct a new approach channel dredging and additional port facilities. Similarly, if the return line for circulating LNG during idle periods is configured separately from the main transfer line of the flow system and insulated, there are significant cost, complexity, and transfer system safety concerns. To increase. However, if the cryogenic fluid transport system is submerged in water as a pipeline supported by the seabed, it will be possible to place a receiving / loading station at a greater distance from the coast, thus requiring a bank or trestle jetty. This eliminates the need for dredging the approach route and constructing an expensive port facility in an area that is indispensable for dealing with a deep draft LNG ship in the area.

  The problem with the transport of cryogenic transport of fluids through the pipeline is that when cryogenic fluid enters the pipeline, it results in substantial shrinkage of most pipe materials, which creates significant thermal stresses. is there.

  In a fluid transfer system located at the bottom of the sea, it is preferable to have an insulated “pipe-in-pipe” configuration for loading / unloading LNG, in order to keep the LNG in transit at cryogenic temperatures, where one or more The annular space between the product pipe and the outer carrier pipe is negative pressure. Product pipe heat shrinkage can be accommodated by multiple and / or large expansion loops in the pipeline system supported by a trestle jetty or a causeway. These pipeline systems with expansion loops are still substantially straight and have a right angle to incorporate the bend into a straight product pipe. By having a primarily straight pipeline in the system, there is still essentially a slight change in the length of the product pipe when temperature changes occur, and heat shrinkage is along the product pipe to incorporate the expansion loop. Locally stresses can be generated due to the curved parts positioned in the direction. In addition, the performance of such an expansion loop in a submarine “pipe-in-pipe” configuration laid on the sea floor can be impaired by sediment, and such a large expansion loop in a submarine “pipe-in-pipe” pipeline Are difficult to manufacture and install. Alternatively, a material with a very low coefficient of thermal expansion such as INVAR ™ (36% nickel steel) can be used to produce an inner pipe carrying the fluid, which is relatively expensive.

  An object of the present invention is to accept the heat shrinkage of product pipes for submarine fluid transport systems. In particular, the present invention forms the product pipe in a non-linear path to add the length of the product pipe into the carrier pipe, and substantially follows the entire length of the product pipe when heat shrinkage occurs. Provided is a fluid transport system for transferring cryogenic fluid between offshore and coastal facilities so that changes in shape and length occur.

  A first aspect of the present invention is a system for transporting a cryogenic fluid comprising a carrier pipe and at least one inner product flow pipe disposed within and insulated from the carrier pipe. The product pipe has a longer deployed length than the carrier pipe, and the total length of the carrier pipe so that the heat contraction of the product pipe due to the temperature change of the product pipe is accepted by the elastic geometric distortion of the product pipe It is equipped with a system that is incorporated in a non-linear path.

  Particularly preferred cryogenic fluids that can be transported by the system are cryogenic fluids, eg, fluids having a temperature of about −160 ° C. such as LNG.

  The excess length of the product pipe as compared to the carrier pipe is accepted by different paths that the product pipe follows along the entire length of the carrier pipe. The product pipe has a longer length than the carrier pipe at a substantially equal temperature, such as before the cryogenic fluid flows through the pipe, and the product pipe will never be shorter than the carrier pipe when a temperature change occurs. The shape of the product pipe is different from the shape of the carrier pipe before the cryogenic fluid flows through the product pipe, so that when the product pipe is cooled by the introduction of the cryogenic fluid, the heat shrinkage is substantially linear. Rather than solely by reducing the length of the product pipe that occurs in a simple pipeline system, it is primarily accepted by changes in the shape of the product pipe, and hence its path through the carrier pipe.

  Preferably, the product pipe is insulated by negative pressure over the entire length of the carrier pipe. Negative pressure is created in the annular space between the carrier pipe and the product pipe.

  Preferably, the non-linear path is a substantially continuously curved path. The product pipe can follow a curvilinear path substantially along its entire length with substantially no straight portion.

  Substantially non-linear product pipes are subject to changes in the length and shape of the product pipe, rather than only the length changes observed in a substantially linear pipeline system subject to thermal shrinkage due to temperature changes. Bring and accept heat shrinkage. The continuously curved product pipe distributes the stress throughout the product pipe during heat shrink compared to a largely straight pipeline system incorporating an expansion loop. In primarily straight pipeline systems, heat shrinkage can create local stresses on the right-angle bends that exist to include loops in the product pipe, and also in the intermediate bulkhead that can fit them. There is.

  Preferably, the product pipe has a regular shape, such as a sinusoidal shape or a steep spiral shape, before the product pipe is exposed to temperature changes. This temperature change can be caused by the flow of cryogenic fluid through the product pipe.

  Preferably, the system comprises two or more product pipes arranged inside the carrier pipe. This makes it possible to increase the amount of fluid transport through the system.

  The system can include a spacer for supporting the product pipe. The spacer can be arranged to prevent the product pipe from becoming a straight line inside the carrier pipe. Preferably, when the product pipe is configured with a flat corrugation, the spacer is disposed about every half wavelength of the product pipe.

  The partition can be attached to the ends of the carrier pipe and the product pipe. The septum can be placed at either end of the pipe to form a heat insulating seal.

  The system further comprises a valve for regulating the flow through the product pipe so that, for example, product fluid recirculation can be achieved to maintain the cryogenic temperature inside the casing pipe when no LNG supply is provided. be able to.

  The system can further comprise a tapping through the carrier pipe to allow suction inside the carrier pipe to negative pressure. This allows for the purification of negative pressure around one or more product pipes to prevent heat flow into the product that causes an increase in product temperature.

2 is a drawing of a sinusoidal product pipe inside a carrier pipe at ambient temperature. FIG. 6 is a drawing of a single product pipe formed in a helical shape inside a carrier pipe at ambient temperature. FIG. 6 is a plan view of a fluid transportation system having four helical product pipes inside a carrier pipe. 1 is a drawing of a coastal termination of a fluid transport system. 2 is a drawing of an offshore termination of a fluid transport system. It is sectional drawing of a fluid pipeline.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. A fluid transfer system for transporting fluids, in particular cryogenic fluids such as LNG, has a “pipe-in-pipe” configuration with a product pipe 1 arranged inside the carrier pipe 2. At either end of the pipe-in-pipe configuration, the components of the septum 6 form an insulated hermetic seal around the carrier pipe. FIG. 1 shows an embodiment of the present invention. The product pipe 1 of FIG. 1 has a sinusoidal shape, but the product pipe may have other similar regular and repeating shapes. Due to the sinusoidal shape, the excess length of the product pipe can be accommodated in a shorter carrier pipe. The pipe 1 is sine inside the carrier before the cryogenic fluid flows through the fluid transport system when the product pipe is at ambient temperature, i.e., when the product pipe and the carrier pipe are at substantially equal temperatures. To have a curved shape, it can be preformed into a sinusoidal shape by axial backing or plastic deformation. When a cryogenic fluid such as LNG flows through the product pipe 1, the LNG cools the product pipe and causes heat shrinkage. The reduction of the length of the product pipe 1 when the product pipe 1 cools is mainly due to the change in the shape of the product pipe by straightening the bend of the pipe, not by the axial strain of the material induced by heat. And cause a change in the path of the product pipe through the carrier pipe. The product pipe is straight within the elastic limit of the pipe. If the product pipe is initially straight, the extension length reduction will be accepted by axial plastic deformation. In addition to changing the shape of the product pipe, the product pipe may also have a change in length, but the length of the product pipe will never be shorter than the length of the carrier pipe. Straightening the product pipe 1 as it cools is aided by a slot in the auxiliary spacer 11. The spacers and slots are positioned so as not to allow the product pipe to be truly straight when at cryogenic temperatures. Linearity that the product pipe is not sufficiently true to allow the product pipe 1 to return to its original configuration when the product pipe returns to ambient temperature, for example, the cryogenic fluid no longer flows through the pipe. It is useful to hold

  By providing a spacer, the product pipe is kept out of contact with the inner surface of the carrier pipe, thereby preventing a heat short circuit that bypasses the vacuum insulation and moderately compresses the controlled refraction of the product pipe. To the selected wavelength, and when the temperature of the product line returns to ambient temperature, the line is restored so that all required controlled refraction or shape is restored and returned to the initial configuration. It is prevented from becoming a straight line at low temperatures.

  The spacer can be made from any suitable material, such as nylon, and can be attached to a product pipe or carrier pipe for manufacturing. Preferably, the pipe is assembled by sliding the finished product pipe with spacers attached to the product pipe upwards within the carrier. The axial spacing of the spacers may be every half wavelength or any other spacing necessary to achieve the required product shape.

  The shape of the distorted product pipe is determined by refracting the product pipe inside the carrier pipe under an axial load applied from the outside during the manufacture of the pipeline system, by pre-plastic working, or by It can be formed by a combination. The axial compressive force load applied to the product pipe at ambient temperature acts on the corresponding tension in the carrier and is transmitted by the end bulkhead. This axial load is much less than the load that would have been imposed by the axial heat shrinkage of the product pipe, which was a conventional linear configuration.

  The wavelength of the distorted shape depends on the inner diameter of the carrier. The product pipe has a deployment length that is sufficient to accept thermal contraction of the product pipe relative to the carrier so that it is not overstressed at cryogenic temperatures, so that this results in a thermal cycle that repeats between cryogenic and ambient temperatures. When undergoing, the cryogenic configuration of the product pipe has sufficient excess strain to return to its original shape.

  Similarly, the wavelength of the sinusoidal product pipe provides any preload required to induce and refract the product pipe inside the carrier pipe at room temperature, and this preload is suitable for moderate stress and / or Or selected to keep the product pipe within a radius of curvature that is allowed to induce only strain.

  The shape of the product pipe is such that when cooled, it accepts heat shrinkage due to a change in shape rather than due to axial strain of the material induced by heat, and the product pipe of the subsea LNG pipeline For manufacturing, materials such as stainless steel 308 or 9% nickel steel can be used.

  The carrier pipe 2 is sufficiently strong enough to be filled with negative pressure to insulate and to accept an external pressure difference of hydrostatic pressure. The carrier pipe 2 may itself be arranged in a further pipe. This further outer pipe acts as a backup insulation layer that can provide additional insulation, and also serves as a damage protection layer.

  The carrier pipe may deviate from a straight line due to, for example, undulations of the seabed where the carrier pipe is located. Such straightness of the carrier pipe is sufficient to achieve the desired initial buckling of the product pipe during ambient temperature manufacturing conditions, and when the product line returns from cryogenic temperature to ambient conditions. Affects how much eccentricity is needed to achieve recovery.

  Any “waveform” of the sinusoid of the product line may be in a horizontal or vertical plane, or may be at an intermediate angle. The orientation is preferably selected to accept the straightness of the carrier pipe depending on whether it deviates more in a plane or elevation.

  In an alternative embodiment of the present invention, the product pipe 1 can have a helical configuration pre-formed at ambient temperature as shown in FIG. The fluid transfer system includes a product pipe 1 that is preformed as a steep spiral in the negative pressure inside the carrier pipe 2. The helical product pipe 1 can be pre-compressed like a spring before being fixed to the carrier pipe 2 by the end bulkhead 6, so that the product pipe 1 when the product pipe 1 cools to cryogenic temperature. The reduction in the unfolded length is accepted by the elastic extension of the helix of the product pipe, like a conventional spring.

  The carrier pipe can support two or more helical product pipes. Multiple product pipes can be sandwiched between multiple threads. FIG. 3 shows one configuration in which four product pipes 1 are arranged on a carrier pipe 2. The spacer 11 helps each of the product pipes not to contact the inner surface of the carrier pipe, and helps prevent the pipes from becoming truly straight at low temperatures. Although a multi-product pipe system is illustrated with four product pipes disposed on the carrier pipe, any number of suitable pipes can be used.

  Spiral product pipes perform conventional methods of seam welding, and further draw an offset parallel to and between the mating edges of the plates forming the seam, thus providing a permanent steep angle Can be produced by inducing a helix into the product pipe.

  An alternative method for manufacturing a spiral product pipe inside the carrier is to place the product pipe as a prefabricated bundle from a remote end into the carrier and into the carrier with the spacer ring already secured to the product pipe. In contrast, it is inserted straight over the length and fixed to a carrier having a septum assembly. At the proximal end of the carrier pipe, a circle with a diameter smaller than the diameter of the carrier, the free end of each product pipe is twisted, and at the same time, each product pipe rotates about its own axis, It winds up so that a spiral may be formed alternately. When the spiral shape is formed, the product pipe can be fixed to the partition wall at the near end. This prevents product pipes from being unwound about their local individual axial centerline. The product pipe is then pre-compressed by pressing the septum against the mating flange on the carrier, providing additional heat shrink capability, and then properly insulating the septum to its mating flange on the carrier. Fixed. Next, the carrier acts on the axial pre-compression load of tension and the axial rotational moment of the torsion of the product pipe that is about to be unwound about the carrier center line. When the product pipe is filled with LNG, the axial pre-compression load changes to tension as the product pipeline contracts to compress the carrier. As the product pipe is twisted and compressed into the spring configuration thus sandwiched, it is assumed that frictional forces accumulate between the spacer and the inside of the carrier pipe. These frictional forces are attracted between the product pipe and the carrier, although the torque and compression applied to the near end bulkhead induces the maximum allowable stress in the product pipe immediately after the near end bulkhead. The relative motion is attenuated until it reaches a fixed point over the length of the carrier pipe, after which the relative movement in the axial direction between the product pipe and the carrier disappears, and at another fixed point, It is applied in such a way that there is also a situation where there is no movement of the product pipe in the circumferential direction relative to the inside of the carrier pipe. The occurrence of this “locked stress” causes the product pipe to be further engulfed and temporarily hinders compression to become a spring. However, if the entire LNG pipeline is manufactured several kilometers long and supported by a coastal roller path that can pull the entire length into the sea, this roller path also causes the entire LNG pipeline to be centered on its long axis. Can be rotated. The process of rotating the product pipe while twisting and compressing it, the product pipe is attracted to form a spiral shape on the product pipe at the near end, and the total length of the carrier is relaxed safely to the far end, Sequentially “unlock” the friction fixing points. When the LNG pipeline is laid from the laying vessel to the sea floor so that the pipeline does not roll, the carrier pipe is filled with seawater and the appropriately designed product pipe has neutral buoyancy inside the casing pipe. It is possible to reduce the formation of the frictional fixing point by preventing the formation of a frictional force that prevents the product pipe from being rotated and compressed. Appropriate facilities are sometimes required to subsequently dewater and dry the casing pipe.

  In particular, the product pipe has been described with an example of a flow system having a sinusoidal or spiral shape. Other shapes may be used for the product pipe if it occurs.

  Each end of the carrier pipe and the product pipe is fixed to the partition wall constituting part. 4 and 5 show details of the bulkhead component for the coastal edge and the offshore edge.

  FIG. 4 shows a coastal termination component for a fluid transfer system. The product pipe 1 disposed in the carrier pipe 2 is a partition wall 6 and forms a heat insulating and airtight seal with the carrier pipe 2 and terminates. The flange 3 welded to the carrier pipe 2 is attached to the coast end end flange 5. The flange can be done with any conventional attachment means such as a nut and bolt component 4. Using appropriate thermal insulation materials 7 and 8, heat from the carrier pipe 2, flanges 3, 5, bolts 4, etc. can flow into the bulkhead 6 and the product pipe 1 and into the fluid inside the product pipe at cryogenic temperature To prevent. The hermetic seal is provided to maintain a negative pressure inside the annular space 9 of the carrier pipe 2. The seal is preferably watertight to prevent water from entering the carrier pipe. The tapping component 10 inside the carrier pipe 2 enables access to the annular space 9 and can generate a negative pressure inside the carrier pipe 2 using an external vacuum pump. Or you may provide a tapping structure part in the inside of a partition. The product pipe 1 is welded to the partition wall 6 to form a structural hermetic seal. FIG. 4 shows the case where there is only one product pipe inside the carrier for the sake of clarity, but a plurality of product lines that all end in the partition may be used. Further, further offshore from the bulkhead, fluids such as LNG are transported to a coastal storage facility using conventional components and maintained at cryogenic temperatures using conventional insulation material 13.

  FIG. 5 shows an embodiment of the offshore termination of the system. A further bulkhead 6 forms an adiabatic and airtight seal on the carrier pipe 2 at the offshore end of the pipe as described above at the coastal end of the flow line system. The heat insulating materials 16 and 12 prevent heat transfer from the carrier pipe 2 to the partition wall 6 and the product pipes 23, 24, 25 and 26. The partition wall 6 can be attached to an insulated cryogenic tanker connection terminal 14. In addition, further offshore from the bulkhead, the LNG is maintained at a cryogenic temperature inside the LNG tanker and unloading gantry using conventional components.

  Fluid transport when there are multiple product pipes inside a single carrier pipe, and during times when LNG is not actually unloaded or loaded through product pipes, such as during LNG tanker ship arrival time Using the valve components at the offshore and coastal terminations of the system, the carrier is vacuum insulated by continuously circulating LNG through one or more product pipes and then back through the other product pipes. The cryogenic temperature can be maintained inside the annular space. FIG. 5 shows an example of a valve component for a carrier pipe having four product pipes at the offshore end of the LNG pipeline. The LNG from the coastal facility is drained through the product pipe 23 by closing valves 17 and 19 and opening the diverting valve 21 to direct LNG from the product 23 to the product pipe 26, and then through the product pipeline 26. A single flow loop can be established that returns. A second LNG loop can be established through the product line 24 from the coastal terminal and back through the product line 25. In this case, the valves 18 and 20 are closed and the direction changing valve 22 is opened. However, when the tanker arrives, all the product pipes are used to quickly unload the fluid by closing the diverting valves 21, 22 and opening the valves 17, 18, 19, 20 so that the tanker can be removed in a short time. You can also return.

  When the LNG is held at the end of the coastal tanker, the valve component is used to circulate the LNG back out through the product pipeline and back, similar to the valve component described for the offshore end. Thus, fluid flow can be diverted from one product pipeline to another product pipeline at the coastal end of the pipeline to establish a flow loop.

  FIG. 6 is a cross-sectional view of a complete LNG pipeline. The product pipe 1 disposed on the carrier pipe 2 is supported by a spacer such as a spacing ring 11 attached to the carrier pipe at an appropriate position along the length of the pipe 1. The distance between the spacers 11 supports the product line inside the carrier, prevents thermal short circuits across the vacuum insulation between the product pipe and the carrier, and the product line when LNG is introduced into the pipe. Depends on the state in which the fluid transport system is arranged to facilitate all axial movement of the product pipe inside the carrier as it cools to cryogenic temperatures and undergoes heat shrinkage. Under the current flow and mechanical protection of the surrounding seawater, a concrete weight covering 15 can be applied to the finished pipeline to provide stability to the submarine pipeline. Groove excavation along the entire length or part of the pipeline can provide protection to the pipeline assembly.

  The completed LNG pipeline can be supported by a trench that gradually slopes from the offshore tanker terminal to the slope of the seabed and from the coastal terminal to the seabed and down the coast. The fluid transport system can be used to unload fluid from a tanker to a coastal terminal, or it can be used to transport fluid from a coastal facility and load fluid into the tanker.

  The LNG pipeline may be generated on a laid ship or manufactured entirely on the coast and then towed in place using facility technology pulled by a conventional submarine pipeline. . Alternatively, the LNG pipeline is partially manufactured and each part is pulled in place and joined together to form a complete line.

  Although the invention has been described with reference to the transfer of cryogenic fluids, particularly LNG, the system is also suitable for transporting other fluids that cause product pipe temperature changes.

Claims (11)

A system for transporting cryogenic fluids,
A carrier pipe,
At least one inner product flow pipe disposed within and insulated from the carrier pipe;
The product pipe has a longer length than the carrier pipe so that thermal contraction of the product pipe due to a temperature change of the product pipe is received by an elastic geometric distortion of the product pipe And incorporated into the entire length of the carrier pipe by following a non-linear path.   The system of claim 1, wherein the product pipe is insulated by negative pressure over the entire length of the carrier pipe.   The system of claim 2, wherein the non-linear path is a substantially continuously curved path.   The system of any one of claims 1 to 3, wherein the product pipe has a sinusoidal shape before being subjected to a temperature change.   The system of any one of claims 1 to 3, wherein the product pipe has a helical shape before being subjected to a temperature change.   The system according to any one of claims 1 to 5, comprising two or more product pipes arranged inside the carrier pipe.   The system of any one of the preceding claims, wherein the carrier pipe comprises at least one spacer for supporting the product pipe.   The system of claim 7, wherein the spacer is disposed about every half wavelength of the product pipe.   The system according to claim 1, comprising a partition wall attached to each end of the carrier pipe and the product pipe.   The system according to any one of the preceding claims, further comprising at least one valve for regulating the flow through the product pipe.   11. A system according to any one of the preceding claims, further comprising a tapping through the carrier pipe to allow the creation of a negative pressure inside the carrier pipe.

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