CA1112262A

CA1112262A - Pipe connectors

Info

Publication number: CA1112262A
Application number: CA338,871A
Authority: CA
Inventors: John D. Mcgugan
Original assignee: Hunting Oilfield Services UK Ltd
Current assignee: Hunting Oilfield Services UK Ltd
Priority date: 1978-11-10
Filing date: 1979-10-31
Publication date: 1981-11-10
Also published as: FR2441785A2; GB2033518A; JPS5572978A; DE2944238A1; NO793387L; NO156216B; DE7931005U1; JPS5985484U; FR2441785B2; DE2944238C2; NO156216C; GB2033518B

Abstract

ABSTRACT
IMPROVEMENTS IN AND RELATING TO PIPE CONNECTORS
The present invention relates to improvements in pipe connectors particularly but not exclusively for use in the drilling and/or completion of off-shore oil and/or gas wells and of the type described in Canadian Patent Application 294,837.
The pipe connector comprises a tubular pin member and a tubular box member telescopically engageable with the pin member, the members having corresponding fruto-conical surfaces which are provided with inter-engageable annular grooves and projections having planar root and crest surfaces lying on common frusto-conical surfaces having the same conicity as the frusto-conical surfaces of the pin and box members. In assembling the pin and box members, the end projections make metal-to-metal contact with the surfaces adjacent the corresponding grooves and the projections and grooves intermediate the end projections and grooves are of lesser axial dimensions and spacing than the end projections and grooves to produce a connector having a lesser axial extent than the connector of application 294,837.

Description

- 1 - .. -i "Improvements in and Relating to Pipe Conn~ctors"

The present invention relates to improvements in pipe connectors particularly but not exclusively designed and adapted for use in connectin~ pipes and other tubular structures for use in the drilling and/or " 5 completion of off-shore oil and/or gas wells.
In oopending C ~ dian Application No, 294,837 filed Jan. 12, 1978, by ~ s~ applieant, ~re is descr~x~ a pipe oonnector ~ris-ing a tubular pin m~ and a tubu~ bo~ m~ which are telescopicall~
engageable, the pin and box menlbers having corresponding 10 frusto-conical outer and inner peripheral surfaces which overlie each other when the members are engaged. To axially lock the pin and box members togethe~, the frusto-conical surfaces have interengageable annular projections and ~rooves. To engage the members together, the box 15 ~lember is ~orced over the pin member, the box member expanding and/or the pin member contracting to enable the projections to ride,into the groo~es. The pin and box membcrs are, irA the preferred embodiment, made of metal ¦ and ensagement is facilitated by supplying liquid under 20 pressure between the frusto-conical surfaces to expand the box member and/or contract the pin member. For the liquid to be effective, seals have to be provided betwe~n the overlapped parts of the f'rusto-conical surfaces of the members and this is simply obtained by 25 arranging the frusto-conical surfaces so that metal-to-metal contact is obtained sufficient to seal or at least restrict the flow of the l,iquid between the over-lapping parts of the surfaces.
In tne above referred to application, the 30 pl~ojections and srooves of the frusto-conical surfaces are substantially equally axially spaced apart alons the a~ial length of the frusto conical surfaces and of equal a~ial extent. The members are dimensioned so that when the n~ember~ are pllshed together each pro~jection comes into 35 n~etal-to-metal conk.-ct wit,ll tl~c part of the frll~to-conical I

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surface upstream of i.ts groove so th~t a seal i~ .initially I provided by each projection and the projeetiorlllas merely i ~ to slide over the upstream pa.r-t of the frus~o-conical surface :into i.ts groove.
It has now been appreciated that it is : unnecessary to provide this metal-to-metal contact betwe~n all projec-t~.~ns and grooves, metal-to-metal se~ling contact being Inerely required at eachi end of the surfaces~
As will become apparent, th;.s enables a substanti.al lO reduetion in the axial length of the frus-to-conical : surfaces and therefore of the pin and box members ~Yith a . consequent substantial saving in material.
Aeeording to one aspeet o~ the present inventi.on there is provided a pipe connector comprising a tubul.ar 15 pin member and a tubular box member teleseopieally en~rage-~ able -with the pin member, the pin me1nber ha~ing a fr~lsto-., eonieal outer peripheral surfaee and 1he box member having t ¦ a eorresponding frusto-eonieal inner peripheral surface . ~hich overlies the frusto~eonieal surface of the pin 20 n1ember when the members are engaged, the frusto-eonical surfaces having a plurality of axially spaeed interengage-able projections and grooves extend.ing eircumferentially i thereof and interengageable to axially lock the pi.n and box members together, wherein the projections and grooves 25 are dimr-~nsioned so that i.nitial metal-to-metal contaet is made be-tween the crest surfaces of the end projections ` at each end of the one frusto-conical surfaee provided i with the projeetions and the surfaees of the other t frusto-eonical surface adjacent the end grooves, the 30 projeetions and grooves intermediate the end projeetions f and groovos bein~ of lrsser axial dimensions and spacing i ¦ than the end projections and grooves, and -the radial dimensions of the projoetions and crrooves aro such th.~t the expan.si.on of the box member ~Ind/or contrae-ti.on Or 135 the pin mcnlber rosultin$ frc)m fOl~citlg tho prO jOCtiOllS .~.~ltO
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; I the corrosponding grooves during engagement of the membcrs , does not exceed the elastic limit of the material of ., tlle members.
¦ Advantageously thc root and crest surfaces of ¦ 5 the projections and grooves lie on f~usto-conical surfaces ¦ parallel to the frusto-conical surfaces of the pin and ~ox members. The projection may be provided on the pin or the box member, with *he corresponding grooves being provided on the other member. Preferably the projections 10 and grooves and surfaces therebetween are arranged so ~ that, considering one of the frusto-conical surfaces it i can be said to ha~-e either projections or grooves~
The radially e~tending end surfaces ~t one end of the projections and grooves can be arranged to transmit 15 forces of compression through the connector and are, for this reason, arranged to extend radially or at a small ! ar.gle to the radial plane. The members may be arranged so that these end surfaces of the projections and grooves , are in positive abutment when the members are engaged.
i 20 For the input of liquid under pressure between the surfaces of the members during enga$ement, a radial inlet duct may be provided in the box member intermediate the ends of the frusto-conical surface th~reof.

Further features and advantages of the present ¦ invention will become apparcnt from the following 30 description of embodiments thereof, given by way o~ example only, with reference to the accompanying drawings, ln which: ¦
Figure 1 is a diagrammatie sectionnl view showirlg part of an emborlinlcnt of a conncctor according 35 to the invelltion;

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Fisure 2 is a par-t sectional, part side view of ¦ the box member o the connector of Flgure 1;
Figure 3 is an enlarsed view of part of one end of the connector of l'igure 1 during enga~ement of the pin 5 and box membe~s; aI~d Figure ~ is a view corresponding to that of Figure 3 showing the pi~ and box members when engagedO
As shown in *he drawings, the pipe connector comprises a tubular pin member l, for connection, e.g. by 10 ~elding, to the end of a pipe 2, and a tubular box member 3 for connection, e~g. by welding, to the end of a pipe 4 to be conn~cted to pipe 2. The pin and box members are teloscopically engageable and have correspondins frusto-conical outer and inner peripheral surfaces 5, 6 15 respectively which overlie one another when the pin member 1 is fully telescoped into the bo~ member 2.
To a~ially loc~ the pin member to the box member, the bo~ member is provided with a plurality of circumferentially e~tending annular grooves 7a, 7b .... 7J, 20 each groove extending in a radial plane and having radially extending end surfaces o, 9 separated by root surface 10.
l The grooves are axially spaced apart by surfaces lla, llb ! ... lli forming the frusto~conical surface 6. The pin , member has a plurality of axially spaced circurnferentially 1 25 extending annular projections 12a~ 12b ~.... 12j correspon-ding to the grooves 7a .~.. 7~, each projection having radiall~ extendin~ surfaces 13, 14 separated by crest surface 15, the grooves being spaced by surfaces 16a, 16 ... 16i formins the frusto conical surface 5.
~, 30 As shown, the root and crest sur-faces 10, 15 lie on frusto-conical surfaces parallel to the surfaces 11, 16 1 -so that all the ~rojections and the groGves are of equal depth. The ~rojections and grooves rnay, .IA~ showrl, e~t~nd over subst~ntially the entire extl?rlt of tlle s~lrfaces 5, 6 35 but m~y extend over a lesser part o:f tlle ~urfnce.
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: The `box member i.s provided with a rad.ial passage 17 communicating with an etx.ially extending recess 1.8 intersecti.ns some of the grooves centrally of the grooved region. The passage is adapted for connection to 5 a source of liquid, e.g. oil, und~r pressure, eOg. at about 175.7 to Zl~.9 Kg/m2 where the pin and bo~ members are made of high tensile steel.
As shown, the connector is intended to transmit compressive forces, eOg. pi.le driving forces, between the 10 pipes to which it is connected an.d to this end the surfaces ~, 13 at one end of each projection and groove are radially extending, or ext~nd at a small angle to the radial plane.
Additionally the connector is arransed so that, when the members are enga~ed, these surfaces 8, 13 are in abutment.
15 As shown this is obtairled by arranging the projections and grooves so that a radial end surface 20 on the box member coutes into abutment wi.th a corresponding radial surface 19 on the pin member to create a force fit between these surface 19, 20 and the surfaces 8, 13. As shown, the 20 projections and grooves are dimonsioned so that there is a slight radial clearance between the othor o~erlying surfaces 15, 16, 10, 11 and radial and axial clearance between surfaces 9, 14. In modifications, the radial clearances between the surfaces I5, 16 and 10, 11 may be 25 omitted so that the pin mcmber is a force fit in the box member.
The frusto conical surfaces 5, 6 and end srooves . 7a, 7i and projections l~a, 12i are arranged and dimensioned so that, when the pin and box members are . 30 pushed together, initial mot.ll-to-metal contact i.s obtained, as shown in Figure 3, between the crest surfaces 15 of the end projections 12a, 12~ of the pin me~nber and the surfaces lla~ of the box mcmber ~djac~nt tho ond grooves 7a, 7j Tho projoction.s and ~s~roo~os intermodi.ate 35 tltese end projoctions and ~roov~s necd n-Jt prov~de mctal-, . , . . d ~__ __.. ... ___ _. __ __ __ _,.. _~.. _ __ .,_,, _, ".__ .. _ __ ~_ ~ ,_,, ,,,__,,_, , _ _,,__,_ ,_,_,_ .__,,_.. _,, .,___,_.~ ,. ~_,, .. _ _~.
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to-meta] conte~ct.
¦ The connector is assembled by tolescoping the ~ members tosether until metal-to-metal contact is obtained ; as shol~n in ~igure 3. At this point liquid under pressure 5 is supplied to the duct 17 and flows along recess 18 between the melllbers up to the regions of mctal to metal l contact. The pressure oP the liquid is set at a level I; sufficient to produce expansion o the box member and/or contraction of the pin member sufficient to permit the lO mombers to be pushed tosether on application of further axial orce. It is found that in effect the liquid no~
only expands the box member and/or contracts the pin member but also lubrioates the contacting surfaces of the members which then form a hydrostatic bearing so that contact is 15 lost. While there is a consequent slight leakage o~ the liquid at the ellds of overlap of the members, the leakage is not sufficient to render the application of the liquid ineffective. It will be appreciated that the frusto-conical surfaces with their projections and grooves are arrcnged 20 so that, in expanding the box member andJor contracting the pin member, the elastic limit of the material of ¦ the pin and box members is not exceeded~
When the members are assembled, it is essential to ensure that no liquid is trapped in any of the groovesO
25 Should liquid be trapped, the corresponding projection I will be unable to ensase fully in thc groove and there will ; therefore be a risk of the connector coming apart. To avoid this possibility, the rocess 18 connected to the liquid inlet duct 17 is extonded axially 50 that liquid 30 in the intermediate srooves can be drained through the recess and duct 17. Any liquid in the end grooves can ¦ cscape round the end o the pin membor and box momber ¦ respectively.
¦ Seals 2l, 22 may be provided irl t~c ~urfacc of ¦35 the pin adjacetlt the ends tllc~oof, son;L Z2 is provLdcd j .: , ..
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primarily to render the interior of the eonneetor fluid ¦ tight. Seal 21 is provided in eonjunetion with seal 22 I to trap oil, not under pressure, between the surfaces to reduce corrosion of the surfaces 5, 6. Under these eircum-5 stanees the duet 17 is also closed.
As has been mentioned above, it has now been appreciated that the intermediate projections and grooves do not have to be arranged to provide initial metal-to metal eontact between a crest o~ a projection and the surfaee up- ¦
10 stream of the corresponding groove. They ean therefore have a lesser axial extent and spacing than the end projections and grooves. In the embodiment described above, the mini-mum a~ial extent and spacing of the projection~ and grooves must merely be such that there is sufficient metal behind 15 each of the force transmitting surfaces 8, 13 that the sur-faees ean withstand the force to be applied thereto. It is found that this requirement produces intermediate protection and grooves which have substantially smaller a~ial extent of spacing so that the overall length of the frusto-conical ¦
¦20 surfaces can be substantially reduced with a substantial ¦ reduciion in the material in the pin and box member~ and therefore a substantial cost saving. As shown, the inter-mediate projections and grooves have approximately half the ~
axial extent and spacing o~ the end prsjections and srooves ¦
~5 whieh produees a conneetor which is less than half the length of connectors in accordance with ~dianappliea~on No.
294,837, when eonsidering eonnectors for transmitting the same axial force and therefore requiring the same nwnber of foree transmitting surfaces 8, 13 of the same radial extent As a consequence o~ this reduetion in axial extentl of the intermediate projections and grooves, during assembly, of the members and after initial metal-to-metal eontact has been made, an intormedia-te projection may, ag shown, have~
to be moved past one or more groove~ upstream of it.q ; 35 eorresponding groove. rO assi~t movemerlt of a projeetion ! _.~, . ~
,, . - 8 -'.`' out of the groove and onto the downstream surface separating the grooves, the end surfaces 14 of the grooves l, and the correspondin~ end surfaces 9 of the projections are .~ inclined At a relatively small angle to the axis.
- l.`. 5 In a pre~erred embodiment, the pin and box members are ~¦ made of high tensile steel and have external and internal diameters of approximately 71cm. The conicity of the , 9` W ~ ',e~

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roots and cr~sts of the groo~es and projections is 2.
¦ Each projection has a height of 0.122cm and each groove has a depth of 0.112cm. The end grooves have a length at the surface of 2.133 cm and the end projections have a 5 length at theïr base of 2.032cm. The surfaces upstream of the end projections and grooves are correspondingly dimensioned. The intermediate grooves and projections may have, for example, half the dimensions of the end grooves and pro~jection so that the overall length of the 10 frusto conical surfaces of the members is 12.70cm with an overall connector length of 24.13cm. This compares with a corresponding connector as described in C~dian Appln. No. I
294,837 which ~ould have a frusto conical surface length of about 42cm and an overall length of-about 53cm.
The rorce transmitting surfaces 8, 13 of the projections and groo~es preferably are inclined at 12 to the radial plane and the other end faces 9, l4 may be inclined at an angle of 75 to the ra~ial plane.
It will ~e appreciated that by using a different 20 angle for the conicity of the frusto conical surfaces of f~ the members and different materials for the members, the foregoing dimensions and numbers of the projections and grooves may be varied.
It will also be appreciated tha-t, while *he 25 above described connector has been described in terms o~
projections pro~ided on the pin member and grooves provided in the box member, this is exactly equivalent to the provision of grooves in the pin member and projections in the bo~ member. Indeed, while the surfaces 131 14 and 15 30 have been described as defining a projection on the pin member, the surfaces 13, 14 and 16 could equally be described as providing a groo~e on the pin member with the corresponding surfaces on the box member providins a projection~ I
There is thu~ providod a pipo connoctor which .

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has a simple construction, is easy to assemble and does ¦ not rcly on moving par-ts to ensure intereng~gcment between I the pin and box members.
It will be appreciated that many different 5 devices may be provided to apply the axial force to the members to bring them into metal-to met~l contact and during application of liquid under pressure between -the frusto-conical surfaces. One such device is described in the said C~an Appln. No. 294,837 and comprises two 10 plates which are split diametrically and arranged to be engaged around a respective one of the members, for example in abutment with surfaces 23, 24. A plurality of hydraulic jacks are arranged to act between the plates, the jacks being angularly spaced apart around the~ axis 15 of the members.
Should the above described connector be required to transmit torque, as well as compressive forces, an inwardly projecting pin may be provided at the inner end of the frusto conical surface of the bGx member for 20 engagement in a recess provided in the leading edge of ,/ tne pin member.

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Claims

CLAIMS:

1. A pipe connector comprising a tubular pin member and a tubular box member telescopically engageable with the pin member, the pin member having a frusto-conical outer peripheral surface and the box member having a corresponding frusto-conical inner peripheral surface which overlies the frusto-conical surface of the pin member when the members are engaged, the frusto-conical surfaces having a plurality of axially spaced interengage-able projections and grooves extending circumferentially thereof and interengageable to axially lock the pin and box members together, wherein the projections and grooves are dimensioned so that initial metal-to-metal contact is made between the crest surfaces of the end projections at each end of the one frusto-conical surface provided with the projections and the surfaces of the other frusto-conical surface adjacent the end grooves, the projections and grooves intermediate the end projections and grooves being of lesser axial dimensions and spacing than the end projections and grooves, and the radial dimensions of the projections and grooves are such that the expansion of the box member and/or contraction of the pin member resulting from forcing the projections into the corresponding grooves during engagements of the members does not exceed the elastic limit of the material of the members.

2. A pipe connector as claimed in claim 1, wherein the projections have planar crest surfaces and the grooves have corresponding planar root surfaces.

3. A pipe connector as claimed in claim 2, wherein the crest and root surfaces of the projections and grooves respectively lie on common frusto-conical surfaces.

4. A pipe connector as claimed in claim 3, wherein the frusto-conical surfaces of the crest and root surfaces of the projections and grooves respectively are parallel to the frusto-conical surfaces of the pin and box members.

5. A pipe connector as claimed in claim 1, claim 2 or claim 3, wherein the angle of conicity of the frusto-conical surfaces of the members is of the order of 2°.

6. A pipe connector as claimed in claim 1, claim 2 or claim 3, wherein the projections and grooves intermediate the end projections and grooves are equally spaced apart along the length of the frusto-conical surfaces.

7. A pipe connector as claimed in claim 1, claim 2 or claim 3, wherein the pin member is a force fit in the box member when fully engaged therewith.

8. A pipe connector as claimed in claim 1, wherein the box member is provided with a radial passage for connection to a supply of fluid under pressure, the passage communicating with an axially extending groove in the frusto-conical surface of the box member and extending centrally of the region provided with the projections and grooves of the assembled pin and box members, for communicating fluid under pressure to the projections and grooves for causing expansion of the box member and/or contraction of the pin member for assisting in the assembly of the connector.

9. A pipe connector as claimed in claim 8, wherein the box member is provided with the annular grooves and the axially extending groove extends axially to communicate with that annular groove adjacent the endgroove at each end of the box member.

10. A pipe connector as claimed in claim 1, claim 2 or claim 3, wherein the pin and box members are adapted for connection to means external thereto for applying an axial force thereto for assisting in assembly of the connector.

11. A pipe connector as claimed in claim 1, wherein each groove in one of the frusto-conical surfaces is defined by a pair of spaced radially extending end surfaces interconnected by a root surface extending parallel to the one frusto-conical surface, and each projection in the other frusto-conical surface is defined by a pair of spaced radially extending end surfaces corresponding to the end surfaces of the corresponding groove and inter-connected by a crest surface extending parallel to the other frusto-conical surface.

12. A pipe connector as claimed in claim 11, wherein the radially extending end surfaces of the grooves and projections respectively intermediate the end grooves and projections are equally spaced apart.

13. A pipe connector as claimed in claim 12, comprising a pair of radially extending faces provided one on the pin member and one on the box member for abutment when the members are engaged and arranged relative to the projections and grooves such that one of the end surfaces of each projection is maintained in metal-to-metal contact with the corresponding end surface of the corresponding groove by abutment between said radially extending faces for transmission of axial forces between the members when engaged.

14. A pipe connector as claimed in claim 13, wherein a clearance is provided between the other end surfaces of the projections and grooves when inter-engaged.

15. A pipe connector as claimed in claim 13, wherein the one radially extending end surface of each projection and the corresponding end surface of each groove is inclined at an angle of the order of 12° to a plane perpendicular to the axis of the connector.

16. A pipe connector as claimed in claim 13, claim 14 or claim 15, wherein the other end surfaces of the projections and grooves are inclined at an angle of the order of 75° to said plane.