COUPLING FOR JUNCTION OF PIPE-IN-PIPE PIPELINE

Abstract

A coupling for pipe-in-pipe pipeline tubing formed of an assembly of sections each incorporating an inner pipe and an outer pipe butt welded to the inner pipe, two successive sections being joined together by the welding of respective inner pipes delimiting a segment of inner pipe, wherein it is formed by a sleeve arranged perpendicularly to the segment and a filler material constituted by a quick-set mortar based on aluminous cement and sand, said filler material being arranged in the free space delimited by the sleeve, said segment and the outer pipes of two successive sections.

Claims

1. A coupling for pipe-in-pipe pipeline tubing formed of an assembly of sections each incorporating an inner pipe and an outer pipe butt welded to the inner pipe, two successive sections being joined together by the welding of said respective inner pipes delimiting a segment of inner pipe, wherein said coupling is formed by a sleeve arranged perpendicularly to said segment and a filler material constituted by a quick-set mortar based on aluminous cement and sand, said filler material being arranged in the free space delimited by said sleeve, said segment and said outer pipes of said two successive sections.

2. Coupling for pipe-in-pipe pipeline according to claim 1, wherein said filler material has the following composition in mass: 30 to 49% of aluminous cement 40 to 58% of diorite sand, 0.6 to 1% of super-plasticizer, 0.5 to 1% of setting accelerator, and adjustment to 100% using water.

3. Coupling for pipe-in-pipe pipeline according to claim 2, wherein said filler material has the following composition in mass: 33% of aluminous cement 55% of diorite sand, 0.7% of super-plasticizer, 0.6% of setting accelerator, and adjustment to 100% using water.

4. Coupling for pipe-in-pipe pipeline according to claim 2, wherein said filler material has the following composition in mass: 39% of aluminous cement 50% of diorite sand, 0.7% of super-plasticizer, 0.6% of setting accelerator, and adjustment to 100% using water.

5. Coupling for pipe-in-pipe pipeline according to claim 2, wherein said filler material has the following composition in mass: 44% of aluminous cement 45% of diorite sand, 0.8% of super-plasticizer, 0.6% of setting accelerator, and adjustment to 100% using water.

6. Coupling for pipe-in-pipe pipeline according to claim 2, wherein said filler material has the following composition in mass: 47% of aluminous cement 41% of diorite sand, 1% of super-plasticizer, 0.9% of setting accelerator, and adjustment to 100% using water.

7. A process to produce a coupling according to claim 1 in which said two sections of pipe-in-pipe pipeline are brought together, and then said inner pipes are welded together, wherein a sleeve is positioned perpendicularly to the segment of said inner pipes and said filler material is injected.

8. The process to produce a coupling according to claim 7, wherein said filler material has the following composition in mass: 30 to 49% of aluminous cement 40 to 58% of diorite sand, 0.6 to 1% of super-plasticizer, 0.5 to 1% of setting accelerator, and adjustment to 100% using water.

9. The process to produce a coupling according to claim 8, wherein said filler material has the following composition in mass: 33% of aluminous cement 55% of diorite sand, 0.7% of super-plasticizer, 0.6% of setting accelerator, and adjustment to 100% using water.

10. The process to produce a coupling according to claim 8, wherein said filler material has the following composition in mass: 39% of aluminous cement 50% of diorite sand, 0.7% of super-plasticizer, 0.6% of setting accelerator, and adjustment to 100% using water.

11. The process to produce a coupling according to claim 8, wherein said filler material has the following composition in mass: 44% of aluminous cement 45% of diorite sand, 0.8% of super-plasticizer, 0.6% of setting accelerator, and adjustment to 100% using water.

12. The process to produce a coupling according to claim 8, wherein said filler material has the following composition in mass: 47% of aluminous cement 41% of diorite sand, 1% of super-plasticizer, 0.9% of setting accelerator, and adjustment to 100% using water.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Other characteristics, advantages and particulars of the invention will become apparent from the additional description given hereafter with reference to the drawings, in which:

[0055] FIG. 1 show a section view of two sections of pipeline assembled together,

[0056] FIG. 2 is a longitudinal section view of the junction coupling according to the invention of a pipe-in-pipe pipeline junction,

[0057] FIG. 3 is a cross section view of the junction coupling according to the invention,

[0058] FIG. 4 is another cross section of the junction coupling according to the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

[0059] The invention will now be described in greater detail. As indicated previously a pipe-in-pipe pipeline is formed of several sections joined together so as to produce lengths of a few hundred to a few thousand metres. The issue is to couple together these different sections and to consolidate the junction between successive sections.

[0060] FIG. 1 shows two sections 1 and 2 of pipe-in-pipe tubing fitted with a coupling 3. It goes without saying that the pipeline is constituted by a great number of sections, according to the wishes of the customer. Each section 1 or 2 comprises an inner pipe 2a, 2b and an outer pipe 4a, 4b between which the annulus thus delimited is filled with thermal insulation, not shown.

[0061] FIG. 2 shows a longitudinal section view of the coupling 3 where the inner pipes 2a, 2b and outer pipes 4a, 4b can be seen. Each outer pipe is classically butt welded onto the inner pipes after its extremities have been flanged as can be seen in the figure. The inner pipes 2a and 2b have been welded together delimiting a segment 5 with a single inner pipe.

[0062] As explained previously, this segment is reinforced by means of a coupling 6 according to the invention that is constituted by a sleeve 7 positioned perpendicularly to the segment 5 and a filler material 8. The sleeve 7 is in the form of a double-cased pipe. The filler material 8 is arranged in the free space delimited by the sleeve 7, said segment 5 and the outer pipes 4a and 4b of the two successive sections 1 and 2.

[0063] This filler material 8 is constituted by a quick-set aluminous cement and sand-based mortar whose composition will be explained after.

[0064] In FIG. 3, which is the axial section along AA in FIG. 2, the inner pipe 2a is shown, with the filler material 8 and the sleeve 7 formed by its inner pipe 9 and outer pipe 10 separated by thermal insulation 11. The filler material 8 can be seen to fully occupy the free space available between the segment 5 and the sleeve 7.

[0065] FIG. 4, which is an axial section view along BB in FIG. 2, shows the inner pipe 2b, the outer pipe 4b, the filler material 8 and the inner pipe 9 of the sleeve 7.

[0066] According to the invention, the filler material 8 is constituted by an aluminous-based cement with the following composition in mass: [0067] 30 to 49% of aluminous cement [0068] 40 to 58% of diorite sand, [0069] 0.6 to 1% of super-plasticizer, [0070] 0.5 to 1% of setting accelerator, and [0071] adjustment to 100% using water.
One skilled in the art may, depending on the technical requirements, determine the composition to be adopted by choosing the appropriate percentage.

[0072] Thus, the following compositions may be used:

Example 1

[0073] 33% of aluminous cement [0074] 55% of diorite sand, [0075] 0.7% of super-plasticizer, [0076] 0.6% of setting accelerator, and [0077] adjustment to 100% using water.

Example 2

[0078] 39% of aluminous cement [0079] 50% of diorite sand, [0080] 0.7% of super-plasticizer, [0081] 0.6% of setting accelerator, and [0082] adjustment to 100% using water.

Example 3

[0083] 44% of aluminous cement [0084] 45% of diorite sand, [0085] 0.8% of super-plasticizer, [0086] 0.6% of setting accelerator, and [0087] adjustment to 100% using water.

Example 4

[0088] 47% of aluminous cement [0089] 41% of diorite sand, [0090] 1% of super-plasticizer, [0091] 0.9% of setting accelerator, and [0092] adjustment to 100% using water.

[0093] The above mortar compositions may be produced in the following manner.

[0094] Firstly, an intimate mixture is made of aluminous cement and diorite sand, the super-plasticizer is then added followed by the water. The intimate mixture thus obtained can be kept soft so long as the setting accelerator is not added. When the coupling is to be made, the accelerator is added to the mortar and mixed in and the resulting mixture must be used very rapidly.

[0095] To make the coupling 3, the inner pipes 2a and 2b are welded together, then the sleeve is placed perpendicularly to the segment 5 covering the outer pipes, respectively 4a and 4b, then the mortar is quickly poured or injected into the free space delimited by the sleeve 7, the segment 5 and the outer pipes 4a and 4b.

[0096] For a filler material intended for temperatures of up to 180 C., the properties of this mortar are excellent, namely: [0097] Setting time: <10 min; the shorter this time the more economically competitive the solution. With a long pre-mixing time, the setting time may be between 3 and 5 mins, after the accelerator has been added. [0098] Compressive strength: [0099] >10 MPa when fresh, [0100] >60 MPa when mature; [0101] Maniability: The mortar can be poured or injected between two concentric pipes with annular space of between 5 and 10 mm at the radius or more, typically up to 80 mm; [0102] No shrinkage upon setting [0103] Resistance to ageing in a marine environment under a pressure of 100 bars, or even up to 220.10.sup.5 Pa, at a temperature of 140 C. or even up to 180 C. [0104] Modulus of elasticity in compression: between 20,000 MPa and 35,000 MPa; [0105] Flexural modulus of elasticity: between 6,000 and 15,000 MPa; [0106] Resistance to cyclic mechanical stress: no deterioration of the mortar between 2 pipes when the pipes and cyclically stressed over a large number of cycles, by flexion for example.

[0107] Typical diameters of pipe-in-pipe tubing are 170 mm and 220 mm, respectively for the inner pipe 2a or 2b and the outer pipe 4a or 4b for the smallest, and can reach 400 mm and 500 mm, respectively for the inner pipe 2a and 2b and the outer pipe 4a and 4b, for the largest sizes installed. The diameters of the pipes of the double-cased sleeve 7 are greater than the diameter of the outer pipe 4a and 4b of the tubing to enable the sleeve to be positioned over the weld.

[0108] Typical clearance between the outer pipe of the tubing and the inner pipe of the sleeve is between 5 mm and 15 mm in the thin parts and the typical clearance between the inner pipe of the tubing and the inner pipe of the sleeve is between 25 mm to 80 mm in the central part. It is this space which is filled with mortar according to the invention.

[0109] The advantage of this mortar is its resistance to ageing at temperatures of up to 180 C. and its setting time of less than 10 mn which makes it able to be used as a filler material for the coupling 7 of offshore pipelines during the laying of such pipelines by offshore barges and for operating temperatures of up to 180 C.

[0110] Another advantage of this mortar is that it can be used for S-lay or J-lay modes of installation as it requires a single pouring or injecting operation to fill the space between the sleeve and the pipeline at the junction and once the sleeve is in position over the weld joining the two sections of pipeline.

[0111] Another advantage of this mortar is that it does not shrink when setting between 2 concentric pipes and with play in the range of 5 mm to 15 mm in the fins or 25 mm to 80 mm in the central part of the junction.

[0112] Another advantage of this junction configuration is the improved mechanical efficiency of the junction of these two pipe-in-pipe sections with the sleeve. In fact, the mechanical properties of such a mortar are greater than those of other hardenable materials such as polyurethane resin or di-polycyclopentadiene (DPCD). The modulus of elasticity in compression of this mortar is in the range of 28,000 MPa whereas it is in the range of 2,000 MPa for a polyurethane resin or DPCD at ambient temperature. The high modulus of elasticity of the mortar enables better transmissions of the mechanical stresses between the pipeline and the sleeve at the junction.

[0113] With identical dimensions, the junction using this mortar as a filler material 8 will have better flexural rigidity than the same junction using a resin or DPCD by way of a filler material. In this configuration, this improved transmission of the mechanical stresses between the pipeline and the sleeve enables a reduction in the mechanical constraints in the single-walled section of the pipeline thereby improving its flexural resistance and its fatigue life.

[0114] Another advantage of this configuration is that the modulus of elasticity in compression of the mortar remains relatively constant over the temperature range of this application whereas this modulus reduces when the temperature increases in a polyurethane resin or DPCD. The mechanical efficiency of the junction is thus relatively constant over the operating temperature range of this application.

[0115] Another advantage of this configuration is that, thanks to the superior modulus of elasticity in compression of this mortar with respect to PU resin, for example, the geometry of the double-cased sleeve (diameter and thickness of pipes, length) can be optimized. In fact, the flexural rigidity of the coupling mainly depends on the length of the sleeve 7, the flexural rigidity of the sleeve 7 and the modulus of elasticity in compression of the filler material 8. Given that the mortar has a modulus of elasticity in compression more than 10 times greater than that of a PU resin or a DPCD, the sleeve 7 may be selected shorter and/or with a lower flexural rigidity (=thinner pipe thicknesses) whilst ensuring the same flexural rigidity of the junction.

[0116] As the doubled-cased thermally-insulated sleeve 7 also plays a role in reducing the thermal losses from the single-cased section of the pipeline, a balance will have to be found for the sleeve geometry that both ensures a flexural rigidity and thermal performance of the junction in line with the pipeline specifications.

[0117] Another advantage of this filler material 8 is that this mortar is a material with a thermal dilatation coefficient in the range of 12.Math.10.sup.6 m/(m.Math.K). This thermal dilatation coefficient is similar to the thermal dilatation coefficient of the steels used for the pipelines and the double-cased sleeve. This enables the thermal constraints operating between the steel pipes and the filler material of the junction to be limited. Indeed, in operation, the inner pipe of the pipeline will be at a temperature of 100 C. or even up to 180 C., the mean temperature of the junction will increase and thermal constraints may appear due to the differences in thermal dilatation between the steels of the pipeline and the filler material. This will not be the case for this configuration using this mortar.

[0118] Another advantage of this configuration is that the inner pipe of the sleeve may be deformed by a few millimetres (from 2 to 10 mm for example) inwards at one or several places along its length to improve the sliding resistance of the sleeve by geometrical impediment.