GB2503320B

GB2503320B - Fluid conduit sealing and connection

Info

Publication number: GB2503320B
Application number: GB1306761.6A
Authority: GB
Inventors: Ollerhead Richard
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-04-13
Filing date: 2013-04-12
Publication date: 2019-09-18
Anticipated expiration: 2033-04-12
Also published as: GB201206498D0; EP2836754A1; WO2013153353A1; GB201306761D0; GB2503320A

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, forexample, the connection and sealing of oil or gas pipes.

Crude oil extracted from certain parts of the world contains a relatively high proportion ofsulphurous impurities and, accordingly, is known as "sour crude”. One of the most significantimpurities 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 thecorrosiveness of sour crude containing significant levels of hydrogen sulphide that evenstainless steel pipes will, within a matter of weeks, suffer corrosion of such a significant degreethat leakage of the sour crude will then result.

2, DESCRIPTION OF RELATED ART

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

While such “dual skin” conduits have been successful in transporting sour crude or sour gaswithout corrosion-related failure of the steel casings, they are, inevitably, more cumbersome anddifficult to connect than elements of a single skin pipeline.

SUMMARY OF THE INVENTION

One aspect of the present invention provides a method of joining first and second fluid conduitswherein the second fluid conduit comprises a connecting collar, each conduit having a casing and asleeve 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 voidbetween the outer casings and sleeves in the region of the abutted sleeve ends the free end of theconnecting collar extending over the free end of the casing of the first conduit; wherein the connecting collar disposed on the second conduit has an inner surface with a radiusgreater than that of the outer surface of the casing of the first conduit; wherein the step of creating a sealed void comprises the step of sealing the casing of the secondconduit to the casing of the first is performed with an annular seal connected to the connectingcollar disposed on the second casing, the annular seal having a sealing lip depending radially inwardinto the interior of the collar and away from the free end of the collar and a seal at the other end ofthe collar between the collar and the second conduit, and injecting sealant into the void, thereby toseal at the junction of the fluid conduits provided by the abutted sleeves of the first and secondconduits.

Another aspect of the present invention provides a pair of mutually connected fluid conduits, eachconduit having a casing comprising an elongate, substantially cylindrical body and connecting collarat one free end of larger diameter than the body, whereby the collar of one casing extends aroundthe body of an adjacent casing; the collar having a free end and a sealing element having a sealinglip depending radially inwardly and away from the free end of the collar and acting between theinterior of the collar and the exterior of the body; a seal at the other end of the collar between thecollar and the conduit; an inner sleeve located inside the casing for conveyance of fluid, whereinmutually adjacent ends of the inner sleeves of adjacent conduits are connected to each other tocreate a fluid conduit; the collar of one conduit and casing body of the adjacent conduitdefining, in conjunction with the sealing element a void between the mutually connected casingsand the adjacent ends of the inner sleeves of adjacent conduits, the void being filled with sealant.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the invention will now be described, by way of example, and with reference tothe accompanying drawings, in which:

Figure 1 is the section between first and second pipe ends according to an embodiment of thepresent invention;

Figure 2 is a section similar to Figure 1, 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 thepipes;

Figures 4 and 5 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 beconnected to form part of a greater fluid conduit are shown. In the present embodiment, the fluidconduit is a cylindrical pipeline and the conduit elements are provided by dual skin cylindricalpipes 10,12. The pipe 10 is already part of a larger pipeline (not shown) and is thus fixed inposition, but has a free end 14 to which the pipe 12 is to be connected. The pipe 12, which is tobe connected to the pipeline, is free to move.

The fixed and free pipes 10, 12 each have a casing 20, 22 and an inner sleeve 30, 32respectively. In the present embodiment, the casings 20, 22 are each cylindrical and made ofstainless steel while the sleeves 30, 32 are preferably made of a material that is inert in thepresence of HZS, relatively strong, light and with some flexibility. One such material, employedin 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 amale and a female end. The male end 30M of the sleeve 30 projects out of the casing of thepipe 10 and is formed by a small axial projection 34, of narrower external diameter. The femaleend 32F of sleeve 32 also projects from the casing 22 of the pipe 12 and has a recess 36 toaccommodate the projection 34, the recess being formed by virtue of its internal diameter beingslightly larger than the remainder of the sleeve 32. The male and female 30M and 32F ends ofthe sleeve are thus adapted for mutual connection by insertion of the projection 34 into theshallow recess 36 and, when connected in this way, ensure good abutment of the sleeves in amanner 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, 32are 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 oftheir mutual engagement is bound with a binding tape 40, in this instance made of a materialwhich can be cured by the application of a suitable resin. This binding with the tape 40 isintended to ensure that a good seal between the pipe ends 30M and 32F is obtained to avoid theunwanted 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 pipes10,12. The proximal end of the casing 22 of pipe 12 has a connecting collar 50 of largerdiameter connected to the remainder of the casing 22 at location indicated by reference numeral52 in a manner providing hermetic sealing of the collar 50 to the exterior of the casing 22, in thepresent example by welding, though other connection mechanisms are possible. The diameterof the connecting collar 50 is selected to be sufficiently large to enable it to fit around the exteriorof the casing 20. The collar 50 retains an inwardly-acting resilient annular seal 60 within asuitably configured recess 62 located at open end. The seal 60 provides good sealingconnection between the casings 20 and 22 in a manner which will be described subsequently inmore detail in connection with figures 4 and 5).

Referring now additionally to Figure 3, once the binding tape 40 has been applied to theconnected, free ends of the sleeves 30, 32 the casing 22 of pipe 12 is then translated axially inthe direction of arrow A in Figure 1. Since the position of sleeve 32 is now fixed relative to thepipe 10, at least in an axial direction, as a result of its connection with the sleeve 30, this motionof the casing 32 therefore necessarily results in relative translation of the sleeve 32 and casing22 of pipe 12 and, accordingly, care is required in order to avoid damage to the sleeve 32 duringthis phase of the connecting process. Translation of the casing 22 continues firstly until theexterior of the casing 20 is located within the mouth of the collar 50 and secondly until theresilient seal 60 has engaged with the outer surface of the casing 20 of pipe 10. Excessiverelative translation of the collar 50 relative to pipe 10 is prevented by an inwardly-projecting stop54 in the interior of the sleeave. Thereafter, the casing 20 of element 12 is then fixed in positionrelative to the terrain across which the pipeline of which it now forms a part extends, thuseffectively also fixing the relative positions of the casings 20 and 22 to each other.

Referring now additionally to Figures 4 and 5, the resilient seal 60 will now be described in moredetail. The seal 60 is typically formed of a suitable elastic sealing material such as anelastomeric material. The seal 60 comprises an axially-extending support ring or root 66. Theseal 60 is retained in the inner surface of the mouth of the collar 50 by location of the root 66 in acorrespondingly shaped slot 68, which is part of the recess 62. A resilient sealing lip 70depends 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 72defining the innermost extent of the sealing lip 70. The bead 72 therefore forms a ring, the innerradius of which is an aperture whose radius is smaller than that of the external radius of thecasing 20 (and, since a further, identical or very similar pipe will subsequently be connected topipe 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 intoengagement with the casing 20 the direction of the arrow A, the entire sealing lip 70 of the seal60 is initially deflected axially in a direction opposite to arrow A. Thereafter, as the casing 20continues to project into the mouth of the collar 50, the free mouth of the casing 20 forces theaperture defined by the ring of the sealing bead 72 open against the tension arising from theelasticity of the elastomeric material of the seal 60. Once the casing 22 has been moved into itsfinal 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 deflectionshown by the arrow B in Figure 5.

Once the casing 22 has been moved into position and the sealing lip 70 has been deflected toapply a sealing force against the exterior surface of the casing 20, a substantially toroidal void80, 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 hermeticallysealed. The void 80 is additionally sealed from the annular channel defined between the interiorof the casings 20, 22 and the exterior of the sleeves 30, 32 by a pair of fibre rings 90, 92respectively which extend around the outside of the sleeves 30 and bear against the innersurface of the casings 20 at their free ends. In order to complete the sealing process a suitableresin sealant, typically one having a curing action upon the fibre binding tape 40 and the fibrerings 90, 92 is injected into the void 80 via an aperture 96. Once the suitable pressure has beengenerated 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 increasesthe pressure in the void 80. The result of this increase in pressure within the void is acorresponding increase in pressure upon the sealing lip 70, the effect of which is to apply adeflecting 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 casing20 of pipe 10 and, as a consequence, to increase the integrity of the seal between the lip 70 andthe 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 pressurewithin the void 80 is increased. A “binder” test may be used in order to establish the pressure within the void 80, thereby todetermine 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 replacingthe plug 98 with a suitable rubber bung, and then passing a pressure gauge through the centreof the rubber bung. Any drop in pressure will necessarily connote a leak further 'up' thepipeline, i.e. in the direction from which the fluid is flowing. Once a loss of pressure has beendetected, it is then possible, by moving along the pipeline (in the direction towards the fluidsource) and sequentially testing the pressure within the voids 80, to locate a leak within thepipeline to within a single length of pipe; the leak being located downstream of the first void 80 atwhich full supply pressure is detected.

Although all elements in a pipeline are, ideally, securely retained upon the substrate over whichthe fluid is transported and the sleeves within the casings are likewise securely retained, it isinevitably 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 thesleeves. Referring now to Figure 6, each of these stabilising collars has a pair of axially spacedretaining rings 102, interconnected by 4 longitudinal stabilising spring elements 106 radiallyspaced at 90° The spring elements 106 bear against the interior of the casing 20 and flexion ofthose elements accommodates relative motion between the casings and sleeves (for example inthe case of thermal expansion and contraction of the stainless steel casings) whilesimultaneously retaining relative position of the sleeve and casing.

Claims

1. A method of joining first and second fluid conduits wherein the second fluid conduit comprises aconnecting collar, each conduit having a casing and a sleeve located inside the casing, the methodcomprising 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 sealedvoid between the outer casings and sleeves in the region of the abutted sleeve ends the free endof the connecting collar extending over the free end of the casing of the first conduit; wherein the connecting collar disposed on the second conduit has an inner surface with a radiusgreater than that of the outer surface of the casing of the first conduit; wherein the step of creating a sealed void comprises the step of sealing the casing of the secondconduit to the casing of the first is performed with an annular seal connected to the connectingcollar disposed on the second casing, the annular seal having a sealing lip depending radiallyinward into the interior of the collar and away from the free end of the collar and a seal at theother end of the collar between the collar and the second conduit, and injecting sealant into thevoid, thereby to seal at the junction of the fluid conduits provided by the abutted sleeves of thefirst and second conduits.

2. A method according to Claim 1 wherein, prior to connection, the sleeve projects from the casingof the second conduit and the method comprising the step, subsequent to abutting the free endsof the sleeves, of translating the sleeve and casing of the second conduit relative to each other.

3. A method according to Claim 1 or 2 wherein 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.

4. A method according to Claim 3 where each conduit has fiber rings at its free end extendingaround the outside of the sleeves and bearing against the inner surface of the casing and whereinan injection of sealant applies pressure to the sealing lip thereby to urge the lip to bear against theouter surface of the first conduit.

5. A pair of mutually connected fluid conduits, each conduit having a casing comprising an elongate,substantially cylindrical body and connecting collar at one free end of larger diameter than thebody, whereby the collar of one casing extends around the body of an adjacent casing; the collarhaving a free end and a sealing element having a sealing lip depending radially inwardly and away from the free end of the collar and acting between the interior of the collar and the exterior ofthe body; a seal at the other end of the collar between the collar and the conduit; an inner sleevelocated inside the casing for conveyance of fluid, wherein mutually adjacent ends of the innersleeves of adjacent conduits are connected to each other to create a fluid conduit; the collar ofone conduit and casing body of the adjacent conduit defining, in conjunction with the sealingelement a void between the mutually connected casings and the adjacent ends of the innersleeves of adjacent conduits, the void being filled with sealant.

6. A pair of conduits according to claim 5 further comprising a binding element, wound around theexterior of mutually abutting ends of the inner sleeves.

7. A pair of conduits according to claim 5 or claim 6, further comprising a pair of sealing ringsdisposed between respective casing bodies and inner sleeves.

8. A pair of conduits according to any one of claims 5 to 7 further comprising an aperture in the collarvia which the sealant is injectable into the void and a stop to close the aperture.

9. A pair of conduits according to any one of claims 5 to 7 wherein the inner sleeves are made ofglass reinforced plastics material.

10. A pair of conduits according to claim 9 comprising the binding element of claim 6 and thesealing rings of claim 7, wherein the binding element and sealing rings are made of a materialcurable by a resin.

11. A pipeline comprising a plurality of pairs of conduits according to any one of claims 5 to 10.