GB2162607A

GB2162607A - Threaded pipe coupling

Info

Publication number: GB2162607A
Application number: GB08520982A
Authority: GB
Inventors: Hidenori Horii; Haruo Kamimura; Hiroo Asakawa; Mitsuaki Hori; Hidenori Yasuoka
Original assignee: Nippon Kokan Ltd
Current assignee: JFE Engineering Corp
Priority date: 1982-03-23
Filing date: 1985-08-21
Publication date: 1986-02-05
Also published as: GB2117469B; GB8520982D0; NL8202098A; GB2117469A; CA1191172A; JPS58142475U; GB2162607B

Abstract

A screw coupling joint for making an end-to-end connection of mutual pipes via a sleeve, by providing a step portion (11) on an inner circumference about an interior of a female threaded member (2) of the coupling joint, so that the step portion and an end portion (13) of a male threaded member (1a) are contacted via packing material (12). Seal B is formed between the smooth portion 9 on the male threaded member and a cooperating smooth surface 10 on the female member. <IMAGE>

Description

1 GB 2 162 607 A 1

SPECIFICATION

Screw coupling joint The invention relates to a screw coupling joint.

Casing pipes or tubing pipes for an oil well or a gas well are many connected each other in the large depth of the earth. For satisfying those serv ices, the coupling portion is required to have suffi cient strength and sealing ability. For one of 75 structures of the conventional coupling joints, the pipe is defined with a male screw on one end thereof and with a female screw on the other end, and provided with a step as a stopper on an outer circumference about the terminal part of the male screw portion. The outer circumference on the front end portion of the male screw and the inner circumference of the female screw are provided with smooth tapering faces. Under a condition that the pipes of such structure are connected at the ends, the front end portion of the female screw is contacted to said step so that a sealing is formed, and the smooth face of the outer circumference at the front end portion of the male screw is con tacted with the smooth face of the inner circumfer ence of the female screw so that another sealing is formed. With respect to this structure having the stopper at the male screw, if the female screw con tacts the stopper of the male screw, the male screw cannot be further advanced. Therefore, in order to provide proper sealing between the smooth surface of the male screw and the smooth surface of the female screw, the diameters of those smooth surfaces should be determined within stringent production tolerance.

With respect to the structure of a coupling joint using a sleeve, generally a female screw is formed on the sleeve, and a male screw is formed about an end of the pipe, and a step is formed on the in terior of the sleeve to serve as a stopper. Tapered smooth faces are provided on the outer circumfer ence on the front end of the male screw and the inner circumference of the interior of the female screw. In this structure, when the front end portion of the male screw contacts said step, a seal is made between the smooth surface of the male screw and the smooth surface of the female screw.

If the male screw contacts the step of the sleeve at its end point, further screwing cannot be effected.

Therefore a very stringent condition is also re quired here as mentioned above.

When the taper of the smooth surface is 1/16 and if the diameter of the pipe changes 0.1mm, the posiiton of the end portion of the female screw or the male screw changes as much as 1.6mm in length of the pipe, and the production tolerance is so severe that it is difficult to form stable sealing.

Further, the above mentioned coupling joint has difficulties as said under.

In the structure of the former coupling joint, there is made clearance between the front end portion of the male screw and the terminal portion of the female screw, and eddy current of fluid is caused in this clearance and corrosion grows there. If the casing pipe were substituted for such structure, the tubing pipe or the drill pipe to be served within the casing pipe would be caught, due to the clearance, at the front end portion of the male screw, to cause damage there. 70 In the structure of the latter coupling joint, since the front end portion of the male screw and the step portion of the female screw contact each other within the coupling joint, there occurs such disadvantage that a corrosion resistant coating thereon comes off due to contact of metal-tometal. The present invention is to provide an improvement of this kind of the coupling joint to overcome the disadvantages mentioned above. 80 An object of this invention is to provide a coupling structure which may form the satisfied sealing without requiring the severe production tolerance. Another object of this invention is to provide a coupling structure which may prevent the corrosion within the pipe at the connection of the coupling joint which is in the form of contacting the front end portion of the female screw to the step portion on the outer circumference about the ter- minal part of the male screw.

A further object of this invention is to provide a coupling structure which may prevent the damage at the inner wall of the coupling of the same form as mentioned when the tubing pipe or the drill pipe is served therein.

Another object of this invention is to provide a coupling structure which may form the required sealing between the outer circumference of the smooth surface at the front end portion of the male screw portion and the inner circumference of the smooth surface at the inner part of the female screw portion, if or although the production tolerance is large in the coupling joint which is in the form of contacting the end portion of the male screw to the step portion at the inner part of the female screw.

Another object of this invention is to provide a coupling structure which may avoid the damage or exfoliation of the corrosion resistant coating.

For accomplishing the above mentioned objects in the screw coupling joint for the pipe to be used in the oil well, which is in the form of directly contacting end to end of the pipes or via the sleeve, the female screw is defined with the step at the in- ner part thereof for contacting to the front end por- tion of the male screw via the packing material to provide one sealing, the other seal is formed be tween the front end portion of the male screw and the packing material.

With respect to the coupling joint in the form of contacting the front end portion of the female screw to the step defined on the outer circumfer ence about the terminal of the male screw, the packing material closes the clearance between the front end portion of the male screw and the terminal part of the female screw.

In the form of contacting the front end portion of the male screw to the step on the inner circumference at the inner part of the female screw, the pro- cluction tolerance is absorbed by compression of 2 GB 2 162 607 A 2 the packing material, and metal contact is prevented between the front end portion of the male screw and the step at the inner part of the female screw.

In the drawings:

Figure 1 is a vertical cross sectional view show ing an embodiment of a coupling for pipe in ac cordance to the present invention, Figure 2 is a vertical cross sectional view show ing a further embodiment of a coupling, Figure 3 is a cross sectional view showing an embodiment of an attaching structure of a packing material, and Figure 4 is a cross sectional view showing the further embodiment of an attaching structure of a 80 packing material.

The embodiments of the invention will be ex plained in reference to the attached drawing.

Figure 1 shows an example where the present invention is applied to the direct connection end to-end of the pipes. 1 a and 1 b are pipe ends to be coupled, one of which is defined by a male screw 3 and the other of which is defined by a female screw 4. The male screw 3 has, at its terminal a step 5 serving as a stopper of the female screw 4.

An outer circumference 6 around the step 5 is fin ished smoothly. An inner circumference 7 at the end portion of the female screw 4 is also finished smoothly. Under circumstance that the step 5 is contacted with an end portion 8 of the female screw 4, a first seal A is provided at said contact and between the outer circumference 6 and the in ner circumference 7.

The outer circumference 9 at the front end por tion of the male screw 3 is defined with a smooth 100 taper surface. This smooth surface is lengthwise structured in curved convex. The inner circumfer ence 10 than the terminal part of the female screw 4 is formed smoothly in taper corresponding to the taper on said outer circumference. Thus, a second 105 seal B is provided by contacting of the outer cir cumference 9 and the inner circumference 10.

In such a structure, a step 11 is provided at the inner part of the female screw 4, more particularly, at the terminal part of the smooth inner circumfer- 110 ence 10, and this step 11 and the front end portion 13 of the male screw 3 are contacted via the pack ing material 12 and provide a third seal C.

Figure 2 shows one example that the present in vention is applied to the coupling structure using 115 the sleeve. The numeral 2 is the sleeve, in which the female screws 4 and 4 are formed in length at the both sides of the inner surface. A center por tion thereof is defined with a convex portion 14 whose both sides serve as the stoppers 11 and 11. 120 Each of the ends la and lb of the pipes is defined with the male screw 3. The center circumference 9 on the front end part of the male screw is finished smoothly in taper. The smooth surface is length wise formed in convex curve. The inner circumfer- 125 ence 10 than the terminal of the female screw is finished smoothly in taper in correspondence to the taper of the outer circumference. The seal B is formed by contacting the outer circumference 9 and the inner circumference 10.

In such a structure, the other seal C is formed by contacting the respective steps 11 to the front ends 13 of the male screws 3 via the packing material 12.

Figures 3 and 4 each show attachment of the packing material 12. In each, a concave groove 15 is formed for holding the packing material 12 of R in cross section. The packing material 12 is fixed by means of baking, adhesive agent or the like to the concave groove 15 and the step 11 with its outer circumference and side face. In each of Figures 3 and 4, the step 11 is formed with obliquity 0, toward the male screw portion with respect to a vertical line thereof, and the packing material 12 is also formed with obliquity corresponding to said obliquity 0, In addition to such a structure, the packing material 12 in Figure 4 is formed on the other side with obliquity in correspondence to which obliquity 02 is provided at the end 13 of the male screw. Due to the step 11, the side face of the packing material 12, and the obliquity at the front end 13 of the male screw portion, the packing material 12 is prevented from protrusion or dropping toward the interior of the pipe. It is preferable that the above oblique angle is not more than 200.

For the packing material, such materials may be used as rubber, Teflon, organic substance such as synthetic resin (for example, fluorine synthetic resin), or metals whose elastic coefficient is lower than the pipe or the sleeve.

There is a coupling joint that the outer circumference of the male screw is straight in the axial direGtion, and the present invention can be of course applied to such a form.

Depending upon the coupling structure of the invention, the seal A and B are formed as shown in Figure 1 and the seal A is formed as shown in Figure 2 by screwing the male screw 3 into the female screw 4. Further, the seal C is formed between the end portion 13 and the packing material 12 compressed by pressing the end portion 13 so that the sealing effect is as a whole more increased.

Furthermore, in the structure where the stopping step is provided at the end of the pipe having the male screw, the packing material 12 closes the clearance between the front end portion of the male screw and the terminal portion of the female screw, so that corrosion to be caused at this clearance is avoided. Since the clearance is cancelled substantially and when the coupling is used for the casing pipe, the damage can be prevented which is caused in that the end portion of the female screw is caught by the drill pipe or the tubing pipe moving within the casing pipe.

With respect to the coupling joint having the structure provided with the step in the female screw as shown in Figure 2, since the male screw 3 is screwed into while compressing the packing material 12 until the outer circumference 9 at the front end part of the male screw 3 closely contacts to the inner circumference 10 of the female screw, the proper seal B may be provided even if the sizing tolerance were large.

Thus, the present invention may be also applied 130 to the coupling structure which directly makes the 3 GB 2 162 607 A 3 end-to-end connection of the pipes and forms the stopping step at the inner part of the female screw, or to the coupling structure which uses the sleeve and forms the stopping step on the outer circumference in the vicinity of the terminal part of the male screw, and to the other forms of the couplings.

Claims

1. Screw coupling joint for an oil well for making directly an end-to-end connection of mutual pipes, or making an end-to-end connection of mutual pipes via a sleeve, wherein a step is provided on an inner circumference at an inner part of a female screw, and the step and a front end of a male screw are contacted via packing material.

2. Screw coupling joint as claimed in Claim 1, wherein the step serves as a stopper at the front end of the male screw, and sealing is provided between an outer circumference of a smooth surface at the front end of the male screw and an inner circumference of a smooth surface at the inner portion of the female screw.

3. Screw coupling joint as claimed in Claim 1, where the step is provided in the vicinity of a ter minal of the male screw to serve as a stopper at the front end of the female screw, and the sealing is provided between the outer circumference of a smooth surface at the front end of the male screw and the inner circumference of a smooth surface at the inner part of the female screw.

4. Screw coupling joint as claimed in Claim 1, wherein the step has a side oblique with respect to vertical line toward the male screw, and the pack100 ing material has an oblique side to fit said oblique side.

5. Screw coupling joint as claimed in Claim 4, wherein the step has a concave groove at an inner circumference thereof for securing the packing ma- 105 terial with its outer circumference.

6. Screw coupling joint as claimed in Claim 4, wherein the male screw has the front end portion oblique toward the outside, and the packing mate rial has an oblique side in opposition to said 110 oblique portion.

7. Screw coupling joint as claimed in Claim 4, wherein the front end of the male screw and the side of the packing material are vertical.

8. A screw coupling joint substantially as her- einbefore described with reference to, and as illustrated in, Figures 2 and 3, or Figures 2 and 3 when modified as in Figure 4, of the accompanying drawings.

Printed in the UK for HMSO, D8818935, 12,85, 7102. Published by The Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.

8. Screw coupling joint as claimed in Claim 4, wherein the packing material is organic substance.

9. Screw coupling joint as claimed in Claim 1, wherein the packing material is metal whose elastic coefficient is not more than the composing ma- terial of the sleeve body.

10. A screw coupling joint substantially as hereinbefore described with reference to, and as illustrated in, Figures 1 and 3, or Figures 2 and 4 of the accompanying drawings.

New claims or amendments to claims filed on Superseded claims 1-10 New or amended claims:- 1. A screw coupling joint for end-to-end con- nections between pipes for oil or gas wells, wherein male screw threads are provided at opposing ends of a first and a second pipe and female screw threads are provided in a sleeve and are adapted to engage the male screw threads of said opposed pipe ends, respectively, and wherein for each of said pairs of cooperating female screw threads in the sleeve and male screw threads at said opposed pipe ends, a step is defined in the in- ner circumference of the sleeve at an inner part of the female screw threads, a front end portion of the cooperating threaded pipe end is contacted with the step via packing material, and a first seal is produced between a smooth surface positioned at an end of the male screw threads and axially tapered in convex form, and the inner circumferential surface of the cooperating female screw threads, and wherein a second seal is effected between each of said steps and the front end portion of the cooperating threaded pipe and by means of the packing material disposed therebetween and engaged therewith.

2. A screw coupling joint as claimed in Claim 1 wherein each step has a side wall which is, in cross-section, oblique with respect to a plane normal to the axis of the pipe, and the packing material has a corresponding oblique side wall to engage against said oblique side wall of the step.

3. A screw coupling joint as claimed in claim 2, wherein each step has a concave groove at an inner circumference thereof for securing the packing material at its outer circumference.

4. A screw coupling joint as claimed in Claim 2 or Claim 3, wherein the front end portion of each threaded pipe is, in cross-section, oblique with respect to a plane normal to the axis of the pipe to define an end surface which converges in the direction towards the opposed step, and the packing material has a corresponding oblique side wall opposed to said oblique front end portion of the pipe 5. A screw coupling joint as claimed in Claim 2 or Claim 3, wherein the front end portion of each threaded pipe and the cooperating side wall of the packing material lie in planes normal to the axis of the pipe.

6. A screw coupling joint as claimed in any preceding Claim, wherein the packing material is an organic substance.

7. A screw coupling joint as claimed in any of Claims 1 to 5, wherein the packing material is metal whose elastic coefficient is not more than the composing material of the engaging parts of the joint.