DE2348657A1 - PIPING SYSTEM FOR LOWEST TEMPERATURE LIQUIDS - Google Patents

Description

Priority; Sept. 29, 1972; V.St.Aj No. 293 343

The invention relates to pipelines for chilled liquids and, more particularly, to a pipeline system for Low-temperature fluids, such as liquefied natural gas, with the pipeline system consisting of an inner steel pipe and a concrete outer tube, which is the inner conduit at the heat contraction under the influence of the low temperatures prevents their operating conditions.

The increasingly widespread use of liquefied Natural gas for heating and industrial purposes has an increased need for cheap and safe means of transportation of the liquefied natural gas from the remote production sites to the urban areas of use evoked. Since large amounts of liquefied natural gas are transported by tankers and cargo ships, it arises a special problem with the transfer of the liquefied

409822/0706

PJRE 3195 - 2 -

Gas to and from the coast, especially if there is long distances are involved.

In the construction of pipeline systems for liquefied natural gases and other fluids which are transported at temperatures which are substantially below the ambient temperature, a number of technical problems must be solved. These problems arise from the physical forces developed in cooling to low temperature operating conditions and from shock and other loads inherent in the environment in which the piping system is installed.

A fundamental problem encountered with piping systems that operate at temperatures well below the Ambient temperature is due to the fact that the pipelines change their length when they switch from ambient to operating temperature cooled or heated from operating to ambient temperature. The degree of expansion or contraction the piping is a function of the material of the piping; Carbon steel, steel alloys, copper and aluminum each have individually different thermal expansion and coefficient of thermal contraction. Typically, pipeline systems are between fixed pumping stations or tanks arranged, and it is therefore necessary to allow the considerable expansion or contraction of the pipeline to be taken into account, which may arise, especially if a pipe run is of considerable length.

A serious problem that frequently arises is that the inner conduit and that provided on its outer side Isolation have unequal expansion coefficients, and so there is a rupture or displacement of the isolation statute. One known solution to this problem is the installation of expansion joints or pieces in a pipe section. The installation of equalizing elbows or pieces is expensive;

A09822 / 0706

PHE 3195 - 3 -

they cannot be buried in the ground and often take valuable space and result in installation problems. Expansion joints are more efficient in terms of space utilization; however, they are quite expensive and add significantly to the cost of a pipe system. Once in a while they are also not reliable in operation. A typical construction for an expansion joint is the 3-leg joint, which opens and closes under the influence of forces in the pipeline.

A major disadvantage with expansion joints is that each expansion joint can accommodate only a limited amount of expansion or contraction and therefore a significant number of expensive prefabricated units must be installed, especially when large temperature changes are involved. For example, the shortening of an approximately 305 m long piece of 9 % nickel steel pipe when cooling from ambient to the temperature of liquefied natural gas, which corresponds to a temperature change of approximately 166 ^° C., can be approximately 0.5 m. Aluminum piping would contract even further. If this significant expansion is not accommodated by a number of expansion joints, the forces at each end of the pipeline can severely damage the pumping or tank systems, or result in unsafe operating conditions.

Another in the construction of piping systems The basic problem that occurs for the absorption of cold substances is that the pipelines often come from the coast remote charging stations must be underwater. Still other piping systems have to be practically in the wild are laid in areas where there are significant temperature and / or water fluctuations, and accordingly the piping systems are subject to changing

409822/0706

PEE 3195 -A-

Environmental forces · Environmental considerations leave it desirable appear to protect the pipeline from these environmental influences by creating a safety barrier for the system provision is made for the pail of a leak. It is desirable that piping systems have one or more secondary barriers contain, which keep the cold and valuable fluid in the line and also prevent fluids from entering, which may be present in the vicinity of the line. This is related to the idea of a gas-tight system to be provided so that cleaning of the insulating space with an inert gas can be carried out in a reliable manner can.

Another that occurs in the construction of piping systems for liquefied natural gas or other cold fluids The problem consists in providing sufficient insulation to prevent heat from entering the line. For pipe systems a large number of isolations have been developed and, overall, they are relatively expensive and vary in size Dimensions difficult to install. A related problem is the creation of cheap and efficient processes for laying the pipeline with its insulation in distant or underwater locations.

A number of systems have been developed which deal with solving the aforementioned problems. One of these Solutions is disclosed in U.S. Patent No. 3,530,680; here relatively extensive mechanical means are provided for pretensioning a steel pipeline by pre-pressing; the prestressed pipe is then placed in an outer steel pipe arranged, and the inner and outer pipes are firmly attached to each other, so that the stresses in the inner line can be transferred to the outer line. When the inner pipeline is in its working condition at low temperature has, it contracts, creating its own

409822/0706

PEE 3195 - 5 -

Compressive stress relieved and the tension on the outer Pipeline is transferred. The constructions shown in said US-PS are relatively complicated and not absolutely suitable for installation in pipelines for the transport of cold fluids, such as liquefied fluids Natural gas.

The object of the invention is to create a pipeline system and a method for producing this system, that is simple, easy to lay and inexpensive and that satisfactorily designs the pipeline in such a way that that the considerable forces and movements that result from a · temperature change between ambient and operating temperatures occur, be absorbed; In particular, a pipeline system for cold liquids is to be created, where the previously used expensive and problematic expansion joints and equalizing elbows or - Pieces with their disadvantages no longer have to be used. This pipeline system should be usable under water and in uncivilized areas and is intended for the pipeline to provide considerable protection against environmental forces, the forces waves or tides, or the movement of underlying terrain. In this pipeline system should There should be barriers to the ingress of external fluids or leakage of cold fluid out of the pipeline prevent in the event of a line break; the piping system should be able to be insulated in a simple and inexpensive manner with easily procured materials.

According to the invention, this object is achieved by a pipeline system for operating temperature fluids consisting of a metallic Inner line for the cryogenic fluid consists, which is essentially free of longitudinal stresses under ambient conditions is. The metallic inner pipe is surrounded by a concrete outer pipe, which together with the inner pipe

409822/0706

PEE 3195 - 6 -

2343657

defines an annular gap. The inner line and the outer pipe are rigidly connected to each other by on the outside of the inner pipe and the concrete outer pipe fortified facilities. When the inner pipe is cooled under operating conditions, they become the inner pipe transferring contracting forces to the concrete outer tube, which results in a compressive stress in this. It is known that concrete has very good compressive strength properties Has. It has now been found that with the construction according to the invention, the degree of contraction of the inner conduit is significantly reduced, with the outer concrete pipe serving to dampen the contraction that would otherwise occur.

The concrete outer tube also provides a considerable amount of external protection for the inner conduit, and so is the combination suitable for installation under water or in uncivilized areas or in places where there is protection against the environment is required. The interspace between the inner conduit and the outer tube is well suited for insulation materials like perlite, which can be pumped into this space in a cheap and easy way.

In the preferred embodiment, ring flanges are attached to the inner conduit and these are on mating plugs assigned to the concrete outer tube. Preferably, an annular rigid spacer is made of insulating material arranged between the puddles connected to the inner line and the puddles of the concrete outer tube.

It was found that in the pipeline system according to the invention the number of required for a pipe run Expansion joints can be reduced or such joints even become superfluous. The high Tensile strength properties of the inner line, which are typically

409822/0706

PKE 3195 - 7 -

wise is an alloy steel, are used, and these stresses are transferred to the concrete outer tube, which has high compressive strength properties. This feature is in contrast to known systems which the longitudinal load limit of the steel pipes does not apply was achieved.

Palis desired, the concrete outer tube can circumferentially and / or be prestressed in the longitudinal direction so that there is greater strength for structural functions. At sections where the pipe runs on scaffolding or between widely spaced storage points, the concrete outer pipe can be biased, which provides further structural resistance. A cylindrical metal or steel shell can be embedded in the concrete pipe and act as a barrier against ingress or leakage by ITuiden. The concrete pipe itself makes a very good one Barrier.

In the preferred embodiment, a long section of pipeline can be used are formed from a number of steel pipe pieces which are welded together end by end by butt welding are. Each of these pipe sections is essentially free of longitudinal stresses under ambient conditions. Each of these pieces of steel pipe is surrounded by a section of concrete pipe with end flanges, and the pipes are from the Inner steel pipe held at a distance by rigid insulating spacers, the insulating spacers being made of polyvinyl chloride or another suitable insulation and. Holding material can exist. A steel ring flange is rigidly connected to the outside of each of the pipe sections, and these ring flanges are sandwiched between the z-q / connecting end flanges of two adjacent ones Concrete pipes. A long piping system of this configuration can be effectively constructed by dismantling

Λ09822 / 0706

PEE 3195 - 8 -

alternating arrangement of inner lines and outer concrete pipes. When the steel inner pipe is cooled down, it contracts, and the steel flanges attached to it compress the outer concrete tubes. The amount the contraction is a puncture of the cross-sectional area of steel and concrete pipes and the modulus of elasticity of concrete and steel. The net amount the contraction is considerably reduced compared to that of the unrestrained steel. The following calculations show the decrease in contraction of the composite system, with

As β thermal contraction per unit length of the steel pipe,

Δ-c = load on the concrete pipe,

A-A = cross-sectional areas of the steel pipe and the concrete pipe,

E_, E = modulus of elasticity of steel and concrete, o (s, Xc = stresses in steel and concrete, 6s, 6c «

O _n α (As - Ac) E ₀ = ((XsAT - Ac) E _o

So ο

In the state of equilibrium, the force in the concrete pipe n is the Sta

((XsAT -

Force in the steel tube (P _n = P ₀ )

- A, cE _ß A _s

Vc ⁺ Vs

The shortening due to thermal contraction of a 1000 barrel section of a 9% nickel steel pipe would be:

409822/0706

PRE 3195 - 9 -

= αΔί L = 51Ο " ⁶ · 330. 1000. 12 = 19.8% about = 50.8 cm.

The shortening of a combined system (assuming a stress i ²

would be so;

Stress in the concrete due to the clamping force = 122 kg / cm ² )

. 1000. 12 = - x x 1000 x 12 = 4.5 "" c
(about 10.1 cm).

To eliminate the shortening of the un-stretched nickel steel pipe ten expansion joints would be required, while in the combined system only two expansion joints would be required to be needed.'

It is possible, under ambient conditions, between the ring flange connected to the inner pipe and that of the concrete pipe associated flange to leave a small gap so that a certain contraction of the line takes place before on the outer tube of voltage is transmitted. The size of the gap depends on the geometry of the system and the operating temperature range eh.

The invention is explained in more detail below with reference to the drawing. Show it:

1 shows a schematic representation of a section

of a piping system for operation at low Temperature between two fixed connection points;

2 shows a detailed side plan view in section a section of the pipeline system along line 2-2 of FIG. 1;

Fig. 3 is an end elevational sectional view of the piping system of Figs. 1 and 2 along the line. 3-3 of Figure 2;

Fig. 4 is a second sectional end elevational view of the piping system of Figs. 1 and 2 along the line Line 4-4 of Figure 2; -

409822/0706

PRS 3195 - 10 -

23A8657

Pig. 5 shows, in section, a side plan view of a pipeline system according to the invention with a Expansion joint; and

Pig. Figure 6 is an end elevational sectional view of Pig's piping system. 5 along line 6-6 by Pig. 5.

In Pig. 1 shows two stationary stations 10 and 12, which can be pumping stations, tanks or other devices, that are assigned to a facility for liquefied natural gas or other cold pluids. A pipeline system 14 is made of a number of 'end-to-end sections, some of which are designated 16, 18 and 20.

Pig. Figures 2, 3 and 4 show in detail parts of each of two pipe sections which are shown schematically! in Pig. I are shown. These two pipe sections are denoted by 22 and 24. The line section 24 consists of a steel inner line 26, which can be carbon steel or alloy steel, for example, depending on the operating conditions, and a concrete outer tube 28. The inner line 26 is essentially free of longitudinal stresses under ambient conditions. The conduit 26 and tube 28 are held in a substantially annular orientation by a rigid spacer 30. The rigid spacer 30 can be made of a hard insulating material such as polyvinyl chloride or balsa wood, and it can be continuous as shown or one or more separate ones There are sections that support the underside of the pipe. When the rigid spacer body is continuously 30, it is desirable to provide it with holes 32 and 34 so that the ring can be filled space 36 between the inner conduit and the outer tube 'with einem- insulation material such as perlite. The insulation material is designated by 38.

409822/0706

PEE 3195 - 11 -

A ring flange. 40 is "for example by welding around the Perimeter of the steel inner line 26 attached around. The splash 40 is reinforced by a series of reinforcement plates 42 also positioned around the circumference of the inner conduit are. Rigid isolation rings 44 and 46 are disposed on each side of the flange 40. These rings are in turn to flanges 48 and 50 of the concrete pipe 28 and the adjacent concrete pipe 78. This is how it works in the configuration shown the annular flange 40 against the flanges 48 and 50 by rigid isolation rings 44 and 46. When the pipeline 26 cools and contracts, the flange shifts. 40 in the longitudinal direction and causes compression of the concrete pipe 28 or 78. The total contraction of the combined system consisting of the metal inner pipe and the concrete outer pipe exists but is considerably less than that of a line that is not constrained in any way.

The left half of Fig. 2 shows an adjacent pipe section 22, which is connected to section 24 previously described. The line section 22 consists of a Steel inner pipe 76 and a concrete outer pipe 78. The inner pipe and the concrete outer pipe are separated from one another by a rigid annular spacer 80 with holes 82 and 84. The inner line 76 is connected to the inner line 26 joined at 85 by butt welding to form a continuous pipeline which under ambient conditions im is essentially free of longitudinal stresses, which however at Contraction is placed under tension under operating temperature conditions.

Successive line sections have ring flanges (not shown), which against corresponding flanges of Concrete outer tubes work. During operation, the entire pipeline system contracts, creating a tightly closed System is formed. By connecting pipe sections

409822/0706

PEE 3195 - 12 τ

22 and 24 together it is possible to have a long pipe section that contracts only a fraction of the length of an unconstrained steel tube. Insulation can be introduced into the annular space after adding each additional line section and Concrete pipe section. Palis desired, can between the plan 40 and the adjacent surface of the isolation ring 44 a small gap can be left in order to allow a slight contraction of the inner conduit by cooling it down, before compressive stress is transferred to the concrete outer tube. By doing this, the inside line internal tensile stress developed under operating conditions can be reduced. Palis such a thing at all Gap is provided, its size depends on the geometry and materials of the system and the operating conditions.

Pig. 5 and 6 show two pipeline sections which are adjacent to one another 100 and 102. Sections 100 and 102 are connected by a conventional expansion joint 104 having a plurality connected by columns 106. The construction of such expansion joints 104 is well known. The line section 102 consists of an inner steel line 108 and a concrete outer tube 110. A continuous cylindrical steel jacket 112 is provided inside the concrete outer tube as a barrier against penetration or leakage of pluids through the concrete wall. The cylindrical wall 112 may be formed from a number of sections of steel jackets 112 and 114. Different configurations are available possible. However, it is desirable to embed a cylindrical steel jacket in the concrete of the tube 110, so that a Barrier function is given. Pig. 5 also shows circumferentially disposed prestressing wires 118 made by known methods are wrapped around the concrete wall. Longitudinally oriented prestressing elements can also be embedded in the tube 110 be.

409822/0706

£ BE3 195 - 13 -

The line section 102 has an annular flange 120 which is welded to the inner line 108, as well as reinforcing plates 122 to accommodate the bending moment developed on the surface of the flange 120 when the system is on Operating temperatures is cooled. The splash 120 rests on a rigid sealing ring 124, which in turn is attached to a Steel jacket 116 rests on one shoulder flange of the concrete pipe 110 dressed. The configuration of Fig. 5 differs from that of Pig. 2-4 in that the adjacent line section 100 does not bear directly on it. The net contraction or expansion forces between the sections 100 and 102 are received in expansion joint 104. This is in a cylindrical steel jacket 130 encapsulated with the extended sections of the steel jacket 116 assigned to the line section 102 and the corresponding elongated sections of the steel jacket associated with the line section 100 is connected. The from the cylindrical steel jacket 130 area enclosed can be filled with insulation to prevent heat from entering through the expansion joint.

Patent claims:

A09822 / 0706

Claims (12)

Patent claims ü che •1. Piping system for cryogenic liquids, characterized "by a metal inner line (26; 108) for the cryogenic fluid, which is essentially free of longitudinal stresses under ambient conditions; a concrete outer tube (28; 110) which surrounds the inner conduit (26; 108) and with this an annular gap (36) defined; and means (40; 120) for rigidly connecting the outside of the inner conduit (26; 108) to the concrete outer tube (28; 110), whereby in the event of thermal contraction of the inner line (26; 108), compressive loads are transferred to the concrete outer tube (28; 110) will. 2. Pipeline system according to claim 1, characterized in that on the inner line (26; 108) ring flanges (40; 120) are attached, the matching paddles (48; 124) are present. 3. Pipeline system according to claim 1, characterized by rigid spacers (30) between the inner line (26) and the concrete outer tube (28). 4. Pipeline system according to claim 1, characterized by insulation material (38) in the Annular space (36) between the inner line (26) and the concrete outer tube (28). 5. Piping system for operating temperature pluide, characterized by 409822/0706 a number of sections of steel inner pipes (26) for the ultra-low temperature fluid, the pipe sections are connected end-to-end by butt welding to form a continuous inner conduit, which under ambient conditions is essentially free of longitudinal stresses; having a number of sections of end flanges (48) Concrete outer tubes (28), each of which surrounds a steel inner line section (26) at a distance and with this defines an annulus (36); an annular steel flange (40) rigidly connected to the outside of each of the inner conduit sections (26), the rests against the end flanges (48, 50) belonging to one another of two adjacent sections of outer concrete tubes (28, 78), whereby during thermal "contraction of the inner line (26) compressive stresses are transferred to the concrete pipe (28, 78) will. 6. Pipeline system according to claim 5, characterized in that on the sides of each annular flange (40) are provided as fitting pieces of insulation rings (44, 46). 7. Pipeline system according to claim 5, characterized in that the concrete pipe circumferentially is biased. 8. Pipeline system according to claim 1, characterized in that g e that in the concrete pipe (110) a continuous steel jacket (112) is embedded as Barrier against leakage. 9. Pipeline system according to claim 1 or 5, characterized in that the annular space (36) with Perlite is filled. 409822/0706 10. Method of forming a piping system for operating temperature fluids, labeled by the following steps: Positioning a first portion of an inner metal conduit (26) that is substantially free under ambient conditions of longitudinal stresses; Positioning a concrete outer tube (28) having a slab (48) around the metallic inner pipe section (26) around at a distance from this so that an annular space (36) is defined? Attaching an annular flange (40) to the outside of the inner line section (26), wherein the flange (40) on the Splash (48) of the concrete pipe (28) rests; Fastening a second section of a metallic inner line (76) on the first section (26), the second line section (76) under ambient conditions essentially is free from longitudinal stresses; Positioning a second concrete outer tube (78) with splash (50) around the second metal inner line section (76) at a distance therefrom to delimit an annular space, wherein a splash (50) of the second concrete outer tube (78) attached to the one on the first inner conduit section (26) Ring flange (40) rests; Repeating the process steps mentioned to form a continuous pipeline system. 11. The method according to claim 10, characterized in that that between the annular flanges (40) and the adjacent paddles (48, 50) of the concrete pipes (28, 78) rigid annular insulating blocks (44, 46) are positioned. 12. The method according to claim 10, marked + by Leaving a gap between the annular flanges (40) of the 409822/0706 Inner line (26) and the splash (48) of the concrete outer tube (28); and cooling the inner conduit (26) causing it to contract and "causes its puddles (40) to rest against the puddles (48) of the concrete outer tube (28). A09822 / 0706 Blank page