PIPE COUPLING

Abstract: The method of joining a coupling member to a pipe end is described. The method is particularly concerned with providing a coupling member (12) on the end of a pipe (10) of composite construction formed from a plurality of helically wound reinforcement strips of steel. The method comprises the steps of forming at least one generally circumferentially directed groove (20) in the outer surface of the pipe wall adjacent the end of the pipe to a depth extending into the reinforcement core, providing a coupling member adapted to fit the end of the pipe overlapping the region of the groove or groove, providing key (32) means to extend between said sleeve and said groove in said pipe, providing a curable resin (34) in the joint area between said pipe and said sleeve and curing said resin to bond said coupling member to said pipe end. The resultant coupling is of increased efficiency in providing both an adhesively bonded and mechanically coupled joint.

Description: PIPE COUPLI NG _ The present invention relates to a method of attaching a coupling member to the end of a pipe Λ particularly to the end of a composite construction pipe formed from a plurality of helically * wound reinforcement strips embedded in a resin In our co-pending international patent application number PCT/GB93/02. l+.fc3 (internal reference ROP0132) of common tiling date herewith, the contents of which are incorporated herein bv reference, we describe a pipe construction comprising a plurality of lavers of steel strip which arc helically wound to form a pipe and embedded in a resin matrix, the pipe further including inner and outer linings of filament wound fibre reinforced plastic. In order to utilise these pipes, it is necessary to be able to ιoin together separate lengths or to join pipe lengths to plant Conventional pipe joining techniques are not directlv applicable either to pipe constructed as described or to the medium to high pressure applications which are envisaged According to a first aspect of the present invention there is provided, a method of joining a coupling member to an end of a composite construction pipe comprising a core formed from a pluralitv of layers of helically wound reinforcing strip embedded in a resin matrix, the method comprising the steps of forming at least one generally circumferentially directed groove in the surface of the pipe wall adjacent the end of the pipe to a depth which penetrates the reinforcing core of the pipe; (preferably to a depth no more than half way through the core), providing a coupling member adapted to fit the end of the pipe and overlapping the region of the e: providing key means to extend between said coupling member and into said groove, providing curable resin in the joint area between the pipe and said coupling member, and curing said curable resin to bond said coupling member to said pipe end Prcferablv the pipe has an internal and/or external lining of fibre reinforced plastic i Preferably the reinforcing strip is of steel, and the coupling member and the key means are preferably also of steel or other material having similar mechanical properties. The resin may be injected into the joint area after fitting the coupling member, anαvor may De coated onto the joint mating faces prior to fitting. In one embodiment, the coupling member may be of tubular construction having a circumferentiallv directed groove or grooves formed in the inner surface thereof and which are axially coincident with the at least one groove on the pipe. The sleeve may be provided with a tangential slot extending through the wall thickness to enable a flexible key member to be inserted into the two axially coincident grooves to extend therebetween. The cooperating groove and key means may be cooperating screw threads. In another embodiment of the pipe joint ofthe present invention, the coupling member may be provided in the form of a sleeve axially split into two halves. Each half may have formed in the inner cylindrical surface thereof a groove or grooves which are axially coincident with the at least one groove in the outer surface of the pipe wall. Separate key members of circular split-ring or part circular form may be provided which extend between both grooves and mechanically lock the pipe and the sleeve together in the axial direction. Alternatively, the sleeve halves may be provided with one or more integral, upstanding, radially inwardly directed key members which extend into the groove or grooves in the pipe. In a further alternative construction, the key members may be provided by placing separate key members into the grooves in the pipe end and bonding and sealing these in place prior to fitting of the coupling member which has cooperating grooves. An advantage of this construction is that a finished and protected pipe unit may be supplied by a manufacturer. The two halves of the coupling member may be positively engaged by an internally tapered collar member push fitted over the sleeve halves. The collar member may be removable or permanently connected to the sleeve member by means of injected curable resin for example. Other means of maintaining the two halves of a split coupling member together may be employed, and may comprise various forms of clamps, either permanent or temporary depending upon the application in addition to adhesive bonding. __?. Bv the method of the present ιn\ entιon the pipe and us coupling member are permanently loined together bv a combination ot mechanical and adhesive means Preferablv the at least one groove extends into but does not extend mote than lialtwav through the total thickness of the reinforcing core This will howe\ er v n, depending upon the pipe diameter and the anticipated loading The load transfer trom the pipe to the coupling member is therefore transmuted bv a combination ot the adhesive bond strength and mechanicallv transmitted load which is based on the interlaminar shear strength ot the pipe construction itself An advantage of the method of the present invention is that the efficiency ot the adhesively bonded joint is improved bv splitting it up into two or more shorter lengths bv the kev means and the grooves in the pipe end and/or coupling member thus reducing the high tensile adhesive stress concentrations at the joint ends Analysis has shown that the efficiency ot adhesively bonded |oints is improved by reducing stiffness in the joint area enabling stresses to be more evenly distributed, which in turn reduces the stress peaks In a joint formed in accordance with the present invention, a degree of additional flexibility is imparted to the pipe end and/or coupling member bv the grooves which thus help to reduce the stress concentrations on each end of the joint We have also found that the efficiency of the joint mav be further enhanced bv the use of geometrical features on the pipe end and/or coupling member Preferably the pipe end or coupling member or both mav e a tapered portion over at least a part of the axial strength of the joint The effect of such tapers is to further reduce stiffness in the joint area which further reduces the stress peaks Desirably also, where more than groove is provided, the key members are of a material, eg ductile steel, which provides some resilience in the axial shear direction whereby to permit a more even distribution ot axial mechanical loads between them The groove and kev member combination ser es not onlv to provide a mechanical locking means in the axial direction but also to div ide the total loint area into separate sections The effect ot this division of the lomt area is to reduce peak stresses reduce total stress within the loint and to provide a more even stress distribution in the loint The consequence of this is to produce a loint having a higher load capability tor a given bond length 1 lie coupling member mav have similar features at its remote end to enable uic juininy together of two pipe lengths in a substantially identical fashion, or the coupling member may be provided with other joining means at its remote end. Such other joining means may comprise, for example, boltable flanges, weldable joints, screw threads, clamping or other locking devices Where there are two or more grooves provided in the outer surface ofthe pipe, these may be provided in stepped manner by providing the grooves at the junctions between or in pipe portions having successively reduced diameters. The curable resin may be an epoxy resin or any other suitable for the application According to a second aspect of the present invention there is provided a coupling member for use in the method of the first aspect, the coupling member comprising a generally tubular body poπion having key means extending radially from the surface thereof, said key means being adapted to engage with generally circumferentiallv extending grooves formed in the cylindrical surface of a cooperating pipe end, there being space between the overlapping surfaces ofthe body portion and the said pipe when assembled together to receive a curable resin to bond said pipe and said coupling member together There may also be provided at the junction between the pipe and the coupling member sealing means to protect the exposed end of the pipe from corrosion. Such sealing means may take the form of resin seals or separate polymeric plastics material seals as an additional member in the pipe joint construction The radially inwardlv extending key means may be formed integrally with the bore ofthe coupling member or may be separate key members adapted to fit into grooves formed in the bore of the coupling member In order that the present invention may be more fully understood, examples will now be described bv way of illustration only with reference to the accompanying drawings, of which. Figure i shows an axial cross section througn the end ol a pipe loined to a coupling member. Figure 2 shows an enlarged axial cross section through part of the joint shown in Fig 1 , Figure 3 shows a perspective view of a pipe end and a second embodiment of a coupling member prior to joining. Figure 4 shows a radial cross section through the loined pipe and coupling member indicated Figure 5 shows a perspective view of a third embodiment of a coupling member; Figure o shows a partial axial cross section through a fourth embodiment of a joint between a pipe and a coupling member. Figure 7 shows a further embodiment of a pipe coupling according to the present invention, and Figures 8 to 10 which show sections through pipes joined together in various ways having sealing means disposed between the exposed ends of the pipe portions. Referring now to the drawings and where the same features are denoted by common reference numerals Figures 1 and 2 show an end of a pipe 10 having a coupling member 12 bonded thereto The pipe 10 comprises an outer layer 14 of a filament wound, fibre reinforced resin material, a core laver 10 of a plurality of helically wound steel strips embedded in a resin matrix and an inner laver 1 8 of a filament wound, fibre reinforced resin material The pipe 10 has the outer layer 14 removed to substantially the same axial extent as that of the coupling member 12 Three circumferential grooves 20 are cut in the outer surface o the pipe and extend into the core layer 16 The coupling member 12 is axiallv split into two halves 22, 24 and each half has szrooves 26 formed in the bore thereof which are axially coincident with the grooves 20 in the pipe The coupling member 12 is also provided with a tlange member 28 having bolt holes 30 tor loining to other pipe sections (not shown) or to plant (not shown) Semi-circular key members 32 are inserted into and extend bevond the grooves 20 and 26 to mechanically lock the pipe and coupling member together in the axial direction A curable resm 34 is injected into the gap between the pipe end surface and the bore ofthe coupling member The resm is cured and adhesively bonds the pipe and coupling member together and also surrounds the key members 32 In effect, the adhesive joint between the two cylindrical surfaces ofthe pipe outer diameter and the couphng member bore is divided into four distinct bands which improves the efficiencv of the bonded joint by reducing stress concentrations at the remote ends ot the joint Figures 3 and 4 show a second embodiment of a joint between a pipe 10 and a coupling member 40 The pipe has a similar construction to that descπbed with reference to Figures 1 and 2 and has three grooves 20 cut in the end The coupling member 40 has three axially coincident grooves 42 cut into the bore 44, each groove 42 having a tangential entry slot 46 cut through the tubular wall 48 of the coupling member The pipe 10 is inserted into the coupling member 40 so that the grooves 20 and 42 are coincident and flexible key members 50 are inserted into the slots 46 to extend around and between the grooves 20, 42 With the pipe and coupling member axially locked together by the key members 50, a resin 52 is injected into the joint gap and is cured to adhesively bond the pipe, couphng member and key members together The coupling member may be provided with any suitable means at its remote end for joining the pipe section to another pipe section or to plant Figure 5 shows a perspective view of a third embodiment of a couphng member 60 and pipe 10 As before with reference to Figures 1 and 2, the couphng member 60 compπses two halves 62, 64 and has grooves 66 to cooperate with grooves 20 in the pipe 10 However, in this embodiment, the couphng member 60 further includes a collar member 68 to lock the two halves 62, 64 together The outer surfaces 70, 72 of the coupling member halves and the bore 74 of the collar member 68 have cooperating tapers Semi-circular key members (not shown) extend between the grooves 20 and 66 As in the previous embodiments, a curable resin is injected into the gap between the pipe and coupling member to adhesively bond them together The coupling halves 62, 64 and bore 74 ofthe collar member may be provided with suitable channels and recesses ( not shown ) such that the iniecteα resin also bonds tne conar to tne outside ot the coupling member halves Figure 6 shows a cross section through a tourth emoouiment ot a ιoιnt according to the present invention In this embodiment howev er the end ot the pipe 10 is formed with three different diameter ponions 80 82 S4 there being circumterential grooves 86, 88, 90 provided at the lunctions between each diameter and extending into the core poπion of the pipe The coupling member 92 (shown in part onlv ) is in two halv es ( only 94 shown in pan), and, instead of grooves to receive separate kev members, has three upstanding, radiallv directed key members 96, 98, 100 formed integrally in the bore Λs before a curable resin 102 is injected into the gap between the pipe and coupling member to adhesively bond them together The iniected resin 102 also forms a seal 104 on the exposed end of the pipe 16 The coupling member 92 is also provided with a tapered poπion 106 In a modification of the embodiment shown in Fig υ the grooves 86, 88 and 90 may be formed within the area of each reduced diameter poπion as shown bv dashed lines 1 10, 1 12 and 1 14 These alternative groove positions have corresponding groove positions m the couphng member 92 Figure 7 shows an embodiment where the cooperating grooves and key members are constituted by helically formed screw threads 120, 122 The pipe end has a helical groove 120 formed in the end whilst the coupling member 124 has an upstanding helical screw thread 122 formed in the bore thereof The mechanical coupling between the pipes is augmented by a resin iniected into the joint area between the components to provide an adhesive bond Figures 8 to 10 show embodiments having different means ot sealing the exposed ends of the pipe Figure 8 shows a couphng member 130 having a tlange feature 132 mating with a similar feature of another couphng shown onlv in dashed lines Prior to fitting ofthe coupling member 130 to the pipe end 134 a sott polvmenc plastics material seal member 136 is bonded to the end of the pipe The seal member 136 has an axial ring portion 138 which is bonded to the pipe bore 140, and a radial ring portion 142 which is bonded to the pipe end 144 Pulling the flanges 132 together on tightening ot two complementary coupling members causes the seal members to engage and seal together and also prevent access to the exposeα pipe ana tace 144. As in previous embodiments, there is a resin adhesive 146 injected into the joint area between the coupling member and the pipe end. Figure 9 shows a joint between two pipe ends 150, 152 connected by a single coupling member 154 comprising two axially split halves (not shown). Prior to fitting the coupling member, the pipe ends are provided with rebates 156 into which is fitted a GRP ring member 15S which is bonded thereto. A compressible polymeric seal 160 is positioned between the pipe ends to protect the exposed end faces 162 ofthe pipe ends. After fitting ofthe coupling member 154, a resin 164 is injected into the joint area to seal the assembly and to adhesively bond the components together. Figure 10 shows an assembly similar to that of Fig. 9, but where the seal means comprises three separate members. Two mating pipe ends 170, 172 are each provided with seal member portions 174, 176. Seal member portion 174 has an axially directed flange portion 178 which is bonded to the bore 180 ofthe pipe end 170, and a radially directed portion 182 having a tlange 184. The seal member portion 176 has an axially directed portion 186 bonded to the bore of the pipe end 172, and a radially directed portion 188 having a flange 190 which has a circumferential groove 192 in the inner diameter thereof The flanges 184 and 190 cooperate to form a seal with the aid of an "O" ring 194 in the groove 192. A resin 196 is injected into the joint area to adhesively bond the coupling member 198 to the pipe ends 170, 172. It will be appreciated that the integrally formed key members of Figure 6 may be replaced with separate key members as shown in other embodiments, and similarly for example, the separate key members shown in Figures 1 and 5 could be replaced with key members formed integrally with the coupling member halves. It is pointed out that although the invention has been described with reference to the bonding of a coupling member to a particular form of composite construction pipe, the method is equally applicable to other similar forms of pipe construction. For example, the inner and outer layers of filament wound fibre reinforced material may either be absent or may comprise lavers of woven fibre or chopped strand mat.

Claims: CLAIMS 1 A method of loining a coupling member to the end of a pipe, the method comprising the steps of forming at least one generallv circumferentiallv directed groove in the surface of the pipe wall adiacent the end ot the pipe providing a couphng member adapted to fit the end of the pipe and ov erlapping the region ofthe groove, providing kev means to extend between said coupling member and into said groove, providing curable resin in the joint area between the pipe and said couphng member, and cuπng said curable resin to bond said coupling member to said pipe end, wherein the pipe is of composite construction comprising a core formed from a plurality of layers of hclicallv wound reinforcing stπp embedded in a resin matrix, and the depth of the said groove penetrates the reinforcing core of the pipe 2 A. method according to Claim 1 wherein the pipe has an internal and/or external lining of fibre reinforced plastic 3 A method according to Claim 1 or Claim 2 wherein the reinforcing strip is steel and the key means and coupling member are of the same material or other material having similar mechanical properties 4 Λ method according to anv one preceding claims wherein said resin may be injected into the joint area between the pipe and the coupling member after fitting of said coupling member to said pipe end 5 A method according to anv one preceding claim wherein the mating faces between said coupling member and said pipe end mav be coated with resin prior to fitting 6 Λ. method according to anv one preceding claim wherein said coupling member is of generallv tubular construction 7 Λ method according to claim o wherein said generallv tubular coupling member surrounds the end ot the pipe and is provided with a tangential slot through the wall thickness, said slot co-operating with a circumferentially extending groove in the coupling member and which groove accepts a key member inserted through said slot to engage with two axially coincident grooves in said coupling member and said pipe. 8 A method according to claim 6 wherein said cooperating groove and key means are cooperating screw threads. 9. A method according to any one of preceding claims 1 to 5 wherein said coupling member is in the form of a sleeve axially split into two halves. 10 A method according to claim 9 wherein said two halves have one or more grooves axially coincident with one or more grooves in said pipe end. 1 1 . A method according to either claim 9 or claim 10 wherein there are separate key members adapted to extend between the groove or grooves in said coupling member and said pipe. 12. A method according to claim 9 wherein said axially split halves have upstanding, radially inwardly directed key members. 13. A method according to claim 9 wherein said pipe end is provided with separate upstanding key members which are bonded and sealed into one or more groove in said pipe end prior to fitting of said coupling member. 14 A method according to any one of preceding claims 9 to 13 wherein said coupling member halves are positively engaged by an outer collar member fitted over the halves. 15 A method according to any one presenting claim wherein said coupling member has at least a portion having a cross section which is tapered away from said pipe end. 16. A method according to any one preceding claim wherein at least a portion of said pipe end is tapered towards its open end. A method according to claim 16 wherein said taper is in the form of progressively stepped portions having different diameters A method according to anv one preceding claim wherein said coupling member is provided with features to enable it to be connected to other coupling members or other pipes or to plant A method according to anv one preceding claim further including the fitting of sealing means adjacent the axial free end of said pipe end A couphng member for use in the method of according to Claim 1, the coupling member comprising a generallv tubular body poπion having key means extending radially from the surface thereof, said kev means being adapted to engage with generally circumferentiallv extending grooves formed in the cylindrical surface of a co-operating pipe end, there being space between the overlapping surfaces of the body portion and of said pipe when assembled together to receive a curable resm to bond said pipe and said coupling member together A couphng member as claimed in Claim 20 wherein the key means extend radially inwards from the bore of the tubular bodv portion and are adapted to engage the generallv circumferentiallv extending groove in the outer cylindrical surface of the pipe end A coupling member according to claim 20 or 1 wherein said generally tubular body portion is axially split into two halves A couphng member according to anv one of claims 20. 21 or 22 wherein said key means are formed integrally with the surface of the generally tubular body portion A couphng member according to anv one of claims 20. 21 or 22 wherein said key means are formed separately from said bodv portion A method of joining a coupling member to an end of a pipe substantially as hereinbefore described with reference to the accompanying description and, Figure 1 and 2; or Figures 3 and 4; or Figure 5; or Figure 6; or Figure 7; or Figure 8; or Figure 9; or Figure 10 of the drawings. A coupling member substantially as hereinbefore described with reference to the accompanying description and Figures 1 and 2; or Figure 3; or Figure 5; or Figure 6; or Figure 7; or Figure 8; or Figure 9; or Figure 10 of the drawings.

Inventors: BOND ALEXANDER EDWIN, ECKOLD GEOFFREY CHARLES, MARSH STUART DAVID, MILLWARD WILIAM ANTHONY, BOND, ALEXANDER, EDWIN, ECKOLD, GEOFFREY, CHARLES, MARSH, STUART, DAVID, MILLWARD, WILIAM, ANTHONY
Applicants: BOND ALEXANDER EDWIN, ECKOLD GEOFFREY CHARLES, MARSH STUART DAVID, MILLWARD WILIAM ANTHONY, ROYAL ORDNANCE PLC, BOND, ALEXANDER, EDWIN, ECKOLD, GEOFFREY, CHARLES, MARSH, STUART, DAVID, MILLWARD, WILIAM, ANTHONY
Application year: 1993
Main classification: F16L23
IPC codes: F16L21, F16L23, F16L37