GB2503320A

GB2503320A - Coupler for abutting dual-skin pipes

Info

Publication number: GB2503320A
Application number: GB1306761.6A
Authority: GB
Inventors: Richard Ollerhead
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-04-13
Filing date: 2013-04-12
Publication date: 2013-12-25
Anticipated expiration: 2033-04-12
Also published as: GB201206498D0; EP2836754A1; WO2013153353A1; GB2503320B; GB201306761D0

Abstract

A pair of dual-skin pipes 10, 12, each pipe comprising a casing 20, 22 and a sleeve 30, 32, are coupled by abutting free ends 34, 36 of sleeves 30, 32, connecting casings 20, 22 to form a sealed void (80, Figure 3) and injecting sealant, for example a resin, into the void, which may be plugged using a plug (98, Figure 4). End 36 of sleeve 32 preferably projects from casing 22. Preferably, casing 22 ends in a collar 50, which is sealed to casing 20 using a sealing ring 62. Collar 50 may comprise a sealing lip 56 that deflects axially to bear against casing 20. Sleeves 30, 32 may be comprised of a material inert to hydrogen sulphide, preferably glass reinforced plastic or carbon fibre, while casings 20, 22 may be comprised of stainless steel.

Description

FLUID CONDUiT SEALING AND CONNECTION

BACKGROUND OF THE INVENTION

1. FIELD OF THE INVENTION

The present invention relates to the sealing and connection of fluid conduits such as, for example, the connection and sealing of oil or gas pipes.

Crude oil extracted from certain parts of the world contains a relatively high proportion of sulphurous impurities and, accordingly, is known as "sour crude". One of the most significant impurilies in sour crude is hydrogen sulphide, which is a powerful reducing agent and, accordingly, extremely corrosive in the presence of metals. Such is the extent of the corrosiveness of sour crude containing significant levels of hydrogen sulphide that even stainless steel pipes will, within a matter of weeks, suffer corrosion of such a significant degree that leakage of the sour crude will then result.

2. DESCRIPTION OF RELATED ART

C') Accordingly, it has been necessary to provide pipes for the transportation of sour crude oil and natural gas which comprise a structural casing, typically of stainless steel, and an inner sleeve within the casing made of a material which does not react with hydrogen sulphide such as glass r fibre or carbon fibre, for example. The structural casing acts to support the inner sleeve against the outward pressure of the fluid flowing through it and additionally protects the sleeve from external, mechanical damage (for example, as a result of external influences such as weather).

While such "dual skin1' conduits have been successful in transporting sour crude or sour gas without corrosion-related fai]ure of the steel casings, they are, inevitably, more cumbersome and difficult to connect than elements of a single skin pipeline.

SUMMARY OF THE INVENTION

One embodiment of the present invention provides a method of joining first and second fluid conduits each having a casing and a sleeve located inside the casing, the method comprising the steps of: abutting free ends of the sleeves of the first and second conduits; connecting free ends of the casings, adjacent the abutted sleeves, in a manner creating a sealed void between the outer casings and sleeves in the region of the abutted sleeve ends; and injecting sealant into the void, thereby to seal the fluid conduit provided by the abutted sleeves of the first and second conduits.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the invention will now be described, by way of example, and with reference to the accompanying drawings, in which: Figure 1 is the section between first and second pipe ends according to an embodiment of the present invention; Figure 2 is a section similar to Figure l, showing abutment of the inner sleeves of the pipes; Figure 3 is a section similar to Figure 2 showing connection and sealing of the casings of the pipes: Figures 4 and S are sections through a detail of Figures 1, 2 and 3; and Figure 6 is a detail of a part of a fluid conduit illustrated in Figure 1;

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to Figure 1, adjacent ends of two separate fluid conduit elements which are to be connected to form part of a greater fluid conduit are shown. In the present embodiment, the fluid conduit is a cylindrical pipeline and the conduit elements are provided by dual skin cylindrical pipes 10,12. The pipe 10 is already part of a larger pipeline (not shown) and is thus fixed in position, but has a free end 14 to which the pipe 12 is to be connected. The pipe ?12, which is to be connected to the pipeline, is free to move. r

The fixed and free pipes 10, 12 each have a casing 20, 22 and an inner sleeve 30, 32 respectively. In the present embodiment, the casings 20, 22 are each cylindrical and made of stainless steel while the sleeves 30. 32 are preferably made of a material that is inert in the presence of H2S, relatively strong, light and with some flexibility. One such material, employed in the present embodiment, is glass reinforced plastic also known colloquially as fibre glass, though other materials such as carbon fibre may also be used. The sleeves 30, 32 each have a male and a female end. The male end 30M of the sleeve 30 projects out of the casing of the pipe 10 and is formed by a small axial projection 34, of narrower external diameter. The female end 32F of sleeve 32 also projects from the casing 22 of the pipe 12 and has a recess 36 to accommodate the projection 34, the recess being formed by virtue of its internal diameter being slightly larger than the remainder of the sleeve 32. The male and female 30M and 32F ends of the sleeve are thus adapted for mutual connection by insertion of the projection 34 into the shallow recess 36 and, when connected in this way, ensure good abutment of the sleeves in a manner which also prevents relative radial motion of the ends 30M and 32F.

Referring now additionally to Figure 2, the male and female ends 30M, 32F of the sleeves 30,32 are brought into mutual engagement by translation of the entire pipe 12 in the axial direction indicated by arrow A in Figure 1. Thereafter, the exterior of the sleeves 30, 32 at the location of their mutual engagement is bound with a binding tape 40, in this instance made of a material which can be cured by the application of a suitable resin. This binding with the tape 40 is intended to ensure that a good seal between the pipe ends 30M and 32F is obtained to avoid the unwanted egress of sour crude oil under pressures as high as 300 bar.

The next stage in the sealing process involves interconnection of the casings 20. 22 of the pipes 10,12. The proximal end of the casing 22 of pipe 12 has a connecting collar 50 of larger diameter connected to the remainder of the casing 22 at location indicated by reference numeral 52 in a manner providing hermetic sealing of the collar 50 to the exterior of the casing 22, in the present example by welding, though other connection mechanisms are possible. The diameter of the connecting collar 50 is selected to be sufficiently large to enable it to fit around the exterior of the casing 20. The collar 50 retains an inwardly-acting resilient annular seal 60 within a suitably configured recess 62 located at open end. The seal 60 provides good sealing connection between the casings 20 and 22 in a manner which will be described subsequently in more detail in connection with figures 4 and 5) Referring now additionally to Figure 3, once the binding tape 40 has been applied to the connected, free ends of the sleeves 30, 32 the casing 22 of pipe 12 is then translated axially in r the direction of arrow A in Figure 1. Since the position of sleeve 32 is now fixed relative to the pipe 10, at least in an axial direction, as a result of its connection with the sleeve 30, this motion of the casing 32 therefore necessarily results in relative translation of the sleeve 32 and casing 22 of pipe 12 and, accordingly, care is required in order to avoid damage to the sleeve 32 during this phase of the connecting process. Translation of the casing 22 continues firstly until the exterior of the casing 20 is located within the mouth of the collar 50 and secondly until the resilient seal 60 has engaged with the outer surface of the casing 20 of pipe 10. Excessive relative translation of the collar 50 relative to pipe 10 is prevented by an inwardly-projecting stop 54 in the interior of the sleeave. Thereafter, the casing 20 of element 12 is then fixed in position relative to the terrain across which the pipeline of which it now forms a part extends, thus effectively also fixing the relative positions of the casings 20 and 22 to each other.

Referring now additionally to Figures 4 and 5, the resUient seal 60 will now be described in more detail. The seal 60 is typically formed of a suitable elastic sealing material such as an elastonieric material. The seal 60 comprises an axially-extending support ring or root 66. The seal 60 is retained in the inner surface of the mouth of the collar 50 by location of the root 66 in a correspondingly shaped slot 68, which is part of the recess 62. A resilient sealing lip 70 depends radially inward into the interior of the collar 50 from the root 66 and, in so doing, projects out of the slot 62. The sealing lip 70 terminates in a substantially circular bead 72 defining the innermost extent of the sealing lip 70. The bead 72 therefore forms a ring, the inner radius of which is an aperture whose radius is smaller than that of the external radius of the casing 20 (and, since a further, identical or very similar pipe will subsequently be conneéted to pipe 12, the external radius of the other, free end of casing 22).

When the casing 22 (which includes the sealing collar 50) of the pipe 12 is moved axially into F engagement with the casing 20 the direction of the arrow A, the entire sealing lip 70 of the seal is initially deflected axially in a direction opposite to arrow A. Thereafter, as the casing 20 continues to project into the mouth of the collar 50, the free moulh of the casing 20 forces the aperture defined by the ring of the sealing bead 72 open against the tension arising from the elasticity of the elastomeric material of the seal 60. Once the casing 22 has been moved into its final position, the sealing lip 70 of the seal 60 has been deflected both axially and forced open (i.e. each point has been moved radially outward). The result is a net deflection akin to that of a "hinging" action around the entire extent of the sealing lip 70, which results in the deflection shown by the arrow B in Figure 5.

Once the casing 22 has been moved into position and the sealing lip 70 has been deflected to apply a sealing force against the exterior surface of the casing 20, a substantially toroidal void 80, defined by the external surface of the connected sleeves 30, 32, the ends of the casings 20, 22 and interior surface of the sealing collar 50 is hermetically sealed or substantially hermetically sealed. The void 80 is additionally sealed from the annular channel defined between the interior of the casings 20, 22 and the exterior of the sleeves 30, 32 by a pair of fibre rings 90, 92 respectively which extend around the outside of the sleeves 30 and bear against the inner surface of the casings 20 at their free ends. In order to complete the sealing process a suitable resin sealant, typically one having a curing action upon the fibre binding tape 40 and the fibre rings 90, 92 is injected into the void 80 via an aperture 96. Once the suitable pressure has been generated inside the void 80, that aperture 96 is then sealed with a plug 98.

Referring now additionally to Figure 5, the injection of sealant into the void 80 further increases the pressure in the void 80. The result of this increase in pressure within the void is a corresponding increase in pressure upon the sealing lip 70, the effect of which is to apply a deflecting force to the sealing lip 70 in the direction generally specified by arrow,C in Figure 5.

this deflecting force causes the lip 70 increasingly to bear against the outer surface of the casing of pipe 10 and, as a consequence, to increase the integrity of the seal between the lip 70 and the outer surface of casing 20. Accordingly, and to within limits, this seal is to a degree self-sustaining because the configuration of the seal 60 is such as to cause an increasingly high sealing force to be applied by the lip 70 on the exterior of casing 20 as the sealant pressure within the void 80 is increased.

A binder' test may be used in order to establish the pressure within the void 80, thereby to determine the integrity of the sealed connection between the mating free ends of the sleeves 30, 32. i.e. to determine whether any sour crude is leaking. Such a test is performed by replacing the plug 98 with a suitable rubber bung, and then passing a pressure gauge through the centre of the rubber bung. Any drop in pressure wil] necessarily connote a leak further up' the pipeline, i.e. in the direction from which the fluid is flowing. Once a loss of pressure has been detected, it is then possible, by moving along the pipeline (in the direction towards the fluid source) and sequentially testing the pressure within the voids 80, to locale a leak within the pipeline to within a single length of pipe; the leak being located downstream of the first void 80 at which full supply pressure is detected.

Although all elements in a pipeline are, ideally, securely retained upon the substrate over which the fluid is transported and the sleeves within the casings are likewise securely retained, it is C') inevitably the case that there will be some relative motion between the casings and the sleeves.

Such motion is stabilised by means of stabilising collars located around the exterior of the 0 sleeves. Referring now to Figure 6, each of these stabilising collars has a pair of axially spaced retaining rings 102, interconnected by 4 longitudinal stabilising spring elements 106 radially spaced at g0 The spring elements 106 bear against the interior of the casing 20 and flexion of C'J those elements accommodates relative motion between the casings and sleeves (for example in the case of thermal expansion and contraction of the stainless steel casings) while simultaneously retaining relative position of the sleeve and casing.

Claims

CLAIMSA method of joining first and second fluid conduits each having a casing and a sleeve located inside the casing, the method comprising the steps of: abutting free ends of the sleeves of the first and second conduits; connecting free ends of the casings, adjacent the abutted sleeves, in a manner creating a sealed void between the outer casings and sleeves in the region of the abutted sleeve ends; and injecting sealant into the void, thereby to seal the fluid conduit provided by the abutted sleeves of the first and second conduits.
2. A method according to Claim 1 wherein, prior to connection, the sleeve projects from the casing of the second conduit and the method comprising the step, subsequent to abutting the free ends of the sleeves, of translating the sleeve and casing of the second conduit ielative to each other.

C')
3. A method according to any one of the preceding claims wherein the step of creating a sealed void comprises the step of sealing the casing of the second conduit to the casing of 0 the first is performed with an annular seal connected to the second casing and having a sealing lip depending radially inward.

C'J
4. A method according to Claim 3 wherein the free end of the second conduit has the casing whose inner surface has a radius greater than that of the outer surface of the free end of the casing of the first conduit, the sealing lip is retained on the inner surface of the free end of the casing of the second conduit and, upon connection of the free ends of the casings, the sealing lip is deflected axially by the outer surface free end of the first conduit.
5. A method according to Claim 4 where an injection of sealant applies pressure to the sealing lip thereby to urge the lid to bear against the outer surface of the first conduit.
6. A pair of mutually connected fluid conduits, each conduit having a casing comprising an elongate, substantially cylindrical body and connecting collar at one end of larger diameter than the body, whereby the collar of one casing extends around the body of an adjacent casing; a sealing element acting between the interior of the collar and the exterior of the body; an inner sleeve located inside the casing for conveyance of fluid, wherein mutually adjacent ends of the inner sleeves of adjacent pipes are connected to each other to create a fluid conduit; the collar of one pipe and casing body of the adjacent pipe defining, in conjunction with the sealing element a void between the mutually connected casings and the adjacent ends of the inner sleeves of adjacent pipes, the void being filled with sealant.
7. A pair of conduits according to claim 6 further comprising a binding element, wound around the exterior of mutually abutting ends of the inner sleeves.
8. A pair of conduits according to claim 6 or claim 7, further comprising a pair of seahng rings disposed between respective casing bodies and inner sleeves.
9. A pair of conduits according to any one of claims 6 to 8 further comprising an aperture in the collar via which the sealant is injectable into the void and a stop to close the aperture.
10. A pair of conduits according to any one of claims 6 to 8 wherein the inner sleeves are made of glass reinforced plastics material.
11. A pair of conduits according to claim 10 wherein the sealant is a resin and the binding C') element and seating rings are made of material curable by the resin.0
12. A pipeline comprising a plurality of pairs Df conduits according to any one of claims 6 to 11. r