CA1260983A - Oilwell tubing connector - Google Patents
Oilwell tubing connectorInfo
- Publication number
- CA1260983A CA1260983A CA000468610A CA468610A CA1260983A CA 1260983 A CA1260983 A CA 1260983A CA 000468610 A CA000468610 A CA 000468610A CA 468610 A CA468610 A CA 468610A CA 1260983 A CA1260983 A CA 1260983A
- Authority
- CA
- Canada
- Prior art keywords
- pipe
- thread
- connection
- strength
- coupling
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Abstract
Abstract of the Invention A connector (20) for oilwell tubing and the like is disclosed which has the same outer diameter (21) as does the tubing joints (8 & 9) that it connects. Tubing joints are formed internally with a tapered thread (6 & 7) having a loadbearing flank angle (75° or more) that negates pullout tendancy. A mating coupling (2) having external threads (3 & 4) may be provided with a bore 10 so as to clear a driftbar. Coupling (2) may be provided with bore (13) extending from (14 to 15) so as to develop substantially, a 100% joint strength.
Description
Oilwell Tubing Connector Technical Field .
The outer diameters of conventional threaded pipe couplings are substarltially ~reater than the outer diameter of the pipe joints that they connect and the same is true for most strings of casing and tubing installed within oilwells, however, several constraints are presented by oilwells that are not normally ~5 present in surface piping systems. Each consecutive string including couplings, must pass within a hole bore diameter established by a drill or by a previously set string of pipe. Additionally, there must be sufficient clcarance between that bore and the maximum diameter of the string being run so as to lower freelywithout sticking and to allow sufficient flow area through the annulus then formed lD for fluids without causing an unacceptable pressure drop caused by friction of the flowing fluid. Thirdly, oilwell strings must withstand a%ial tension and compression loads caused by the weight of miles of pipe that may be hanging within the well. Further, oilwell strings may be subject to external fluid pressures being greater than internal pressures to tllereby introduce tendency to collapse.
15 For these and other reasons, joints with upset ends and ~ligh cost "premium connections" have been introduced to work in presence of such constraints.
However, such solutions result with the outer diameters of connections being greater than the outer diameter of the pipe joints that they connect. There do exist, connections for pipe not having upset ends v,lherein Gne end of a joint 20 is threaded externally and the other end is threaded with a mating interr.al thread such that joints can be screwed together to result in a connection with ar~ outel diameter no larger than the pipe mid-section. However, suc~l joints, such as Hydril ~J Premium tubing connections enjoy only 42% axial tension strength as compared to the unthreaded pipe wall, about the same as non-upset API tubing 25 connections. Presently, due to diameter constraints, a typical oilwell pipe program may be: 5~ OD x 2 ~/8 OD x 1.6 OD. To be far more advantageous for use as disclosed in my co-pending application filed herewith and entitled "Method and Means to Pump a Well," a 2 7/8 OD x 1.6 OD x 1.05 OD can of'ten make an installation possible due to clearance or cost reasons that the typical prograrn30 above could not and in every case, a less expensive and a more efficient installation should result. Many tons of steel per oilwell may therefore be saved from waste.When a pipe having no reduced wall thickness contains fluid pressure, the axial stress within that wall caused by fluid pressure is approximately one-half of the circumferential stress within that wall caused by the same pressure and 35 therefore a like amount of mechanical axial stress may be applied by pipe weignt or the like, without exceeding the circumferential stress. Reductior, of the pipe wall thickness a~ by a thread formed on a joint o non-upset pipe, will therefore reduce still further, the magnitude of axial stress that may be dedicated to support pipe weight.
There is therefore a substantial need for a tubular connector with an outer diameter no greater than the pipe outer diameter and with an inner diameter that may be selected to be the largest inner diameter congistent with the axial strength required, all with no loss of the connector's ability to seal against fluid pressure.
Background Art A flush joint tubular connection made by the Hydrill Co., and covered by numerous patents comprise a Eirst straight thread, a second straight thread of sufficient diameter to pass within the bore of the first thread and a tapered mating seal between the two joints of tubing which i5 a premium joint of high cost and according to published data, enjoys only 42 axial strength with regard to the pipe wall.
Standard A.P.I. non-upset tubing connections comprise couplings having outer diameters considerably larger than the pipe outer diameter but still only enjoy approximately 42~
efficiency as above. A.P.I. does list a "turned down" collar outer diameter to increase clearance between strings, however, the "turned down" diameter still exceeds sub~tarltially the pipe outer diameter.
Coberly U.S. Patent 3,005,414 is~ued October 24, 1961 requires a tubing string to convey fluid power to a downhole pump, a string to convey exhausted power fluid from the -2a-downhole pump to the surface and a third string to convey well fluid from the pump to the wellhead. He depicts three parallel strings set within a large casing and makes no mention of the use of flush joint pipe run concentrically.
Disclosure of Invention .
The present invention provides a connector for non-upset joints of oilwell tubing or the like, having a tubular coupling formed with tapered external threads thereon for mating with tapered internal threads formed within the ends of the non-upset tubing joints to be connected~
The coupling may be formed of a material having a higher strength than the material from which the tubing joints are formed so as to allow higher circumferential stresses within the small end of the male threads which is of a thinner wall than the tubing wall thereby adjacent, so as to provide a higher sealing force between the mating threads in the primary seal area~ The use of higher strength material for the coupling also provides a higher axial load capacity than would be provided should the male thread be formed on the tubing joint.
So a~ to nullify the pullout tendency inherent in a non-upset tubing thead having conventional 30 thread flanks, a thread form is provided that has a load bearing flank angle of 15 or less, the exact degree depending on such factors as the pipe diameter, the wall thickness and the material strength.
3~
As taught by my series of patents beginning with U.S. 2,766,82~ which have enjoyed worldwide commercial success for over 30 yeurs in the oilfield, the sp~ce industry and the nuclear in~ustry, the taper of the external thre~d is formed at a lesser angle than the taper of the internal thread so as to ensure a maximum 05 primary sealing tendency at the smallest possible pressure area so as to minimize the axial load imposed on the connector due to internal fluid pressure. The present invention utilizes this feature only in combination with several other features The coupling may be provided with a shoulder to abut the end of the tubing 10 joint upon full makeup, should conditions require precise makeup lengths. ~o as to preclude excessive circumferential stresses of one cooperating threaded member before full makeup of the two, the wall thickness of the two near the small end of the engaged threads may be dimensioned inversely proportional to the strengths of the materials of each. Since moduli of elasticity is 15 substantially the same for both members, both members will therefore be stressed to substantially the same percentage o~ their respective material strengths.
Should the innermost diameter of the connector be of prime importance, the coupling bore may be dimensioned slightly larger than the standard drift diameter for that size tubing, to result in a short coupling as may provide, for~ instance, a 6296 connector efficiency. However, should axial ioint strength be c~f pri~ne importance, the coupling bore may be dimensioned slightly smaller than the standard drift diameter, to result in a long coupling as may provide a connector of 95 to 100% efficiency. The internal thread within the tubing joint nl.ay be formed of sufficient dimension to receive either coupling to thereby
The outer diameters of conventional threaded pipe couplings are substarltially ~reater than the outer diameter of the pipe joints that they connect and the same is true for most strings of casing and tubing installed within oilwells, however, several constraints are presented by oilwells that are not normally ~5 present in surface piping systems. Each consecutive string including couplings, must pass within a hole bore diameter established by a drill or by a previously set string of pipe. Additionally, there must be sufficient clcarance between that bore and the maximum diameter of the string being run so as to lower freelywithout sticking and to allow sufficient flow area through the annulus then formed lD for fluids without causing an unacceptable pressure drop caused by friction of the flowing fluid. Thirdly, oilwell strings must withstand a%ial tension and compression loads caused by the weight of miles of pipe that may be hanging within the well. Further, oilwell strings may be subject to external fluid pressures being greater than internal pressures to tllereby introduce tendency to collapse.
15 For these and other reasons, joints with upset ends and ~ligh cost "premium connections" have been introduced to work in presence of such constraints.
However, such solutions result with the outer diameters of connections being greater than the outer diameter of the pipe joints that they connect. There do exist, connections for pipe not having upset ends v,lherein Gne end of a joint 20 is threaded externally and the other end is threaded with a mating interr.al thread such that joints can be screwed together to result in a connection with ar~ outel diameter no larger than the pipe mid-section. However, suc~l joints, such as Hydril ~J Premium tubing connections enjoy only 42% axial tension strength as compared to the unthreaded pipe wall, about the same as non-upset API tubing 25 connections. Presently, due to diameter constraints, a typical oilwell pipe program may be: 5~ OD x 2 ~/8 OD x 1.6 OD. To be far more advantageous for use as disclosed in my co-pending application filed herewith and entitled "Method and Means to Pump a Well," a 2 7/8 OD x 1.6 OD x 1.05 OD can of'ten make an installation possible due to clearance or cost reasons that the typical prograrn30 above could not and in every case, a less expensive and a more efficient installation should result. Many tons of steel per oilwell may therefore be saved from waste.When a pipe having no reduced wall thickness contains fluid pressure, the axial stress within that wall caused by fluid pressure is approximately one-half of the circumferential stress within that wall caused by the same pressure and 35 therefore a like amount of mechanical axial stress may be applied by pipe weignt or the like, without exceeding the circumferential stress. Reductior, of the pipe wall thickness a~ by a thread formed on a joint o non-upset pipe, will therefore reduce still further, the magnitude of axial stress that may be dedicated to support pipe weight.
There is therefore a substantial need for a tubular connector with an outer diameter no greater than the pipe outer diameter and with an inner diameter that may be selected to be the largest inner diameter congistent with the axial strength required, all with no loss of the connector's ability to seal against fluid pressure.
Background Art A flush joint tubular connection made by the Hydrill Co., and covered by numerous patents comprise a Eirst straight thread, a second straight thread of sufficient diameter to pass within the bore of the first thread and a tapered mating seal between the two joints of tubing which i5 a premium joint of high cost and according to published data, enjoys only 42 axial strength with regard to the pipe wall.
Standard A.P.I. non-upset tubing connections comprise couplings having outer diameters considerably larger than the pipe outer diameter but still only enjoy approximately 42~
efficiency as above. A.P.I. does list a "turned down" collar outer diameter to increase clearance between strings, however, the "turned down" diameter still exceeds sub~tarltially the pipe outer diameter.
Coberly U.S. Patent 3,005,414 is~ued October 24, 1961 requires a tubing string to convey fluid power to a downhole pump, a string to convey exhausted power fluid from the -2a-downhole pump to the surface and a third string to convey well fluid from the pump to the wellhead. He depicts three parallel strings set within a large casing and makes no mention of the use of flush joint pipe run concentrically.
Disclosure of Invention .
The present invention provides a connector for non-upset joints of oilwell tubing or the like, having a tubular coupling formed with tapered external threads thereon for mating with tapered internal threads formed within the ends of the non-upset tubing joints to be connected~
The coupling may be formed of a material having a higher strength than the material from which the tubing joints are formed so as to allow higher circumferential stresses within the small end of the male threads which is of a thinner wall than the tubing wall thereby adjacent, so as to provide a higher sealing force between the mating threads in the primary seal area~ The use of higher strength material for the coupling also provides a higher axial load capacity than would be provided should the male thread be formed on the tubing joint.
So a~ to nullify the pullout tendency inherent in a non-upset tubing thead having conventional 30 thread flanks, a thread form is provided that has a load bearing flank angle of 15 or less, the exact degree depending on such factors as the pipe diameter, the wall thickness and the material strength.
3~
As taught by my series of patents beginning with U.S. 2,766,82~ which have enjoyed worldwide commercial success for over 30 yeurs in the oilfield, the sp~ce industry and the nuclear in~ustry, the taper of the external thre~d is formed at a lesser angle than the taper of the internal thread so as to ensure a maximum 05 primary sealing tendency at the smallest possible pressure area so as to minimize the axial load imposed on the connector due to internal fluid pressure. The present invention utilizes this feature only in combination with several other features The coupling may be provided with a shoulder to abut the end of the tubing 10 joint upon full makeup, should conditions require precise makeup lengths. ~o as to preclude excessive circumferential stresses of one cooperating threaded member before full makeup of the two, the wall thickness of the two near the small end of the engaged threads may be dimensioned inversely proportional to the strengths of the materials of each. Since moduli of elasticity is 15 substantially the same for both members, both members will therefore be stressed to substantially the same percentage o~ their respective material strengths.
Should the innermost diameter of the connector be of prime importance, the coupling bore may be dimensioned slightly larger than the standard drift diameter for that size tubing, to result in a short coupling as may provide, for~ instance, a 6296 connector efficiency. However, should axial ioint strength be c~f pri~ne importance, the coupling bore may be dimensioned slightly smaller than the standard drift diameter, to result in a long coupling as may provide a connector of 95 to 100% efficiency. The internal thread within the tubing joint nl.ay be formed of sufficient dimension to receive either coupling to thereby
2~ add versatility by selection of couplings at the time of use. For instance- short couplings may be used in the lower portion of a string so as to provide maximum internal clearance and thereby reduce flow resistance; long couplings may be used in the upper portion of a string so as to provide greater axial strength asrequired by higher axial loads due to weight of the string; all with use of like30 tubing joints.
Brief Description of the Drawin~
Figure 1. depicts a vertical section of a connector in accord with the present invention.
Figure 2. illustrates a thread form in accord with the present invention.
Brief Description of the Drawin~
Figure 1. depicts a vertical section of a connector in accord with the present invention.
Figure 2. illustrates a thread form in accord with the present invention.
3~ Figure 3. illustrates a thread form in accord with conventional tubing joint threads.
_ Detailed Description of the InYention Figure 1 depicts tubular connection shown generally at 20 comprisirlg coupling 2 with tapered external threads 3 formed on an upper portion and having~ like .hreads 4 formed on a lower portion, so as to mate in sealing engagement ~i ith tapered in.ernal threads 6 and 7 formed within joints of tubing ~ ~ 9, respecth~ely, 05 to be connected.
Coupling 2 may comprise inner diameter 10, upper end surface 11 and lower end surface 12, said end surfaces not extending for the full length of internal threads 6 and 7, when it is desired to have a connector with an inner diameter that will pass the industry standard "drift bar" for that size tubing. Such a 10 connector, as limited by the tension area resulting between the root diameterof the last engaged thread as at 12, and the tubing outer diameter, may provide an axial tension strength of approximately two-thirds that of the pipe wall strength.
Should a connector having a higher axial strength be required, coupling 2 1~ may be formed with inner diameter as at 13, upper end surface as at 14 and lower end surface as at 15. The coupling thereby extending for substantially the full ~ffective length of the internal threads so as to provide a connector having an axial strength substantially equal to the pipe wall strength.
Since typical tubing joints have lengths of sixty times or more the lengths 20 of couplings that connect them, the couplings may be formed of material much stronger than the material the joints are formed of without causing significant increase of cost for the entire string. The use of higher strength rnaterial forthe coupling makes possible a higher axial strength for the connector 20 because, the strength of the coupling at neck section 1~ is increased and because, collapse ~5 resistance of the pipe end as at 12 is increased to thereby increase the pullout strength also. To further increase the pullout strength of the connector, a thread form as depicted in Figure 2 may be used for the mating threads as opposed to the most common thread form used on oilwell tubulars, depicted in Figure 3.
The form of Figure 3 has a loadbearing flank angle of 30 which effects ~?n angle 30 of 30~ between the vertical and a line drawn normal to the flank. Assuming an angle of friction of 5, elementary vector analysis will show that the form depicted in Figure 2 results in a pullout strength of 2~ tirne that of Figure 3.Reduction of the flank angle still further, can virtually eliminate tendancy to pullout. The thinner the tubular walls of the threaded members, the weaker 35 the pullout strength when the 30 flank angle is used, however, by use of a smaller ~oadbearing flank angles, the pullout tendancy of a thinwalled connection can be reduced to a level of no concern.
So as to ensure a seal diameter for the connector of least diameter anà
therefore the least axial fluid load" the taper of the external thread may be 40 made slightly less than the taper of the internal thread. Such a condition also allows maximum radial compression of the connector so at end surface 12 adjaccrlt pipe joint wall as at 17 which mav be formed thicker than the adjacent coupling wall. Thus, upon makeup, end 12 will compr ess rnore than wall 17 cxparlds due to the difference in thicknesses, the moduli of elasticity being considered sub-05 stantially the same. Since coupling 2 may be made of higher strength matelialthan tubing joints 8 or 9, the thickness may be dimensioned such that stresscs in walls at 12 and 17 are substantially at the same percentage of the yield strength of which the members are formed.
Connector 20 mav comprise shoulder 18 formed on the end of joint 9 and 10 shoulder 19 formed on coupling 2 intermediate thread 4 and the outer diame.er~1 of coupling 2. The mating threads may be dimensioned so as to makeup as shown in Figure 1 or should greater bending strength or greater tortional strength be desired, the mating threads may be dimensioned and given closer tolerances so as to allow shoulders 18 and 19 to abut upon makeup.
_ Detailed Description of the InYention Figure 1 depicts tubular connection shown generally at 20 comprisirlg coupling 2 with tapered external threads 3 formed on an upper portion and having~ like .hreads 4 formed on a lower portion, so as to mate in sealing engagement ~i ith tapered in.ernal threads 6 and 7 formed within joints of tubing ~ ~ 9, respecth~ely, 05 to be connected.
Coupling 2 may comprise inner diameter 10, upper end surface 11 and lower end surface 12, said end surfaces not extending for the full length of internal threads 6 and 7, when it is desired to have a connector with an inner diameter that will pass the industry standard "drift bar" for that size tubing. Such a 10 connector, as limited by the tension area resulting between the root diameterof the last engaged thread as at 12, and the tubing outer diameter, may provide an axial tension strength of approximately two-thirds that of the pipe wall strength.
Should a connector having a higher axial strength be required, coupling 2 1~ may be formed with inner diameter as at 13, upper end surface as at 14 and lower end surface as at 15. The coupling thereby extending for substantially the full ~ffective length of the internal threads so as to provide a connector having an axial strength substantially equal to the pipe wall strength.
Since typical tubing joints have lengths of sixty times or more the lengths 20 of couplings that connect them, the couplings may be formed of material much stronger than the material the joints are formed of without causing significant increase of cost for the entire string. The use of higher strength rnaterial forthe coupling makes possible a higher axial strength for the connector 20 because, the strength of the coupling at neck section 1~ is increased and because, collapse ~5 resistance of the pipe end as at 12 is increased to thereby increase the pullout strength also. To further increase the pullout strength of the connector, a thread form as depicted in Figure 2 may be used for the mating threads as opposed to the most common thread form used on oilwell tubulars, depicted in Figure 3.
The form of Figure 3 has a loadbearing flank angle of 30 which effects ~?n angle 30 of 30~ between the vertical and a line drawn normal to the flank. Assuming an angle of friction of 5, elementary vector analysis will show that the form depicted in Figure 2 results in a pullout strength of 2~ tirne that of Figure 3.Reduction of the flank angle still further, can virtually eliminate tendancy to pullout. The thinner the tubular walls of the threaded members, the weaker 35 the pullout strength when the 30 flank angle is used, however, by use of a smaller ~oadbearing flank angles, the pullout tendancy of a thinwalled connection can be reduced to a level of no concern.
So as to ensure a seal diameter for the connector of least diameter anà
therefore the least axial fluid load" the taper of the external thread may be 40 made slightly less than the taper of the internal thread. Such a condition also allows maximum radial compression of the connector so at end surface 12 adjaccrlt pipe joint wall as at 17 which mav be formed thicker than the adjacent coupling wall. Thus, upon makeup, end 12 will compr ess rnore than wall 17 cxparlds due to the difference in thicknesses, the moduli of elasticity being considered sub-05 stantially the same. Since coupling 2 may be made of higher strength matelialthan tubing joints 8 or 9, the thickness may be dimensioned such that stresscs in walls at 12 and 17 are substantially at the same percentage of the yield strength of which the members are formed.
Connector 20 mav comprise shoulder 18 formed on the end of joint 9 and 10 shoulder 19 formed on coupling 2 intermediate thread 4 and the outer diame.er~1 of coupling 2. The mating threads may be dimensioned so as to makeup as shown in Figure 1 or should greater bending strength or greater tortional strength be desired, the mating threads may be dimensioned and given closer tolerances so as to allow shoulders 18 and 19 to abut upon makeup.
Claims (19)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A high efficiency connection for joints of oilwell tubing or the like, comprising: a joint of pipe having no increase in wall thickness near the ends thereof, formed at each end with tapered internal threads a tubular coupling formed at each end with tapered external threads for sealing engagement with said internal threads so as to connect two joints of pipe together, the threads being of sufficient length and taper such that the pipe wall strength in the area of the smallest diameter of thread engagement is at least three-fourths of the nominal pipe wall strength.
2. The invention of claim 1 further comprising: a neck at the base of the external thread being formed with a cross-section wall area less than the nominal cross-section wall area of the pipe; the coupling being formed of a material sufficiently stronger than the pipe material such that the external thread of the coupling can contract further than it could were it made of the pipe material, so as to effectively seal a higher fluid pressure.
3. The invention of claim 1 further comprising: the coupling being formed with a bore of smaller dimension that the pipe bore.
4. The invention of claim 1 wherein the threads are formed with load flanks and stab flanks, comprising: the load flanks being formed at an angle of 75° or greater with respect to the tubular axis; the stab flanks being formed at an angle of lesser degree with respect to the tubular axis, the load flanks and the stab flanks being connected at the roots and crests by cooperating radii such that upon full make-up of the connection, increased sealing engagement is effected along the full thread engagement length.
5. The invention of claim 1 wherein: the strength of the pipe wall at the thread root adjacent the last engaged thread toward the smaller diameter end of the taper is greater than 75% of the pipe wall strength at mid-section of the pipe so as to provide a high strength connection for non-upset pipe.
6. The invention of claim 1 wherein: the wall strength of the pipe at the thread root adjacent the last engaged thread toward the smaller diameter end of the taper is substantially equal to the pipe wall strength at mid-section of the pipe so as to provide a connection strength greater than the pipe strength.
7. The invention of claim 1 further comprising: the coupling being formed with a shoulder so as to abut the end of the pipe joint upon full make-up of the connection.
8. The invention of claim 7, further comprising:
the threads and shoulders being dimensioned such that circumferential compressive stresses at the small end of the male thread are substantially near the unit yield strength of the material from which the coupling is formed.
the threads and shoulders being dimensioned such that circumferential compressive stresses at the small end of the male thread are substantially near the unit yield strength of the material from which the coupling is formed.
9. The invention of claim 1 wherein the inner diameter of the coupling is greater than the drift diameter of the pipe.
10. The invention of claim 1 wherein the thread depth is less than one-sixth of the pipe wall thickness.
11. The invention of claim 1 wherein the internal threads extend substantially to the pipe bore.
12. The invention of claim 1 further comprising:
the external thread being formed on a taper of smaller included angle than is the taper of the internal thread such that full make-up of the connection, a first predetermined circumferential stress is effected in the coupling at the smallest diameter of the external thread and a second predetermined circumferential stress of less magnitude than the first stress is effected in the pipe wall at the largest diamter of thread engagement.
the external thread being formed on a taper of smaller included angle than is the taper of the internal thread such that full make-up of the connection, a first predetermined circumferential stress is effected in the coupling at the smallest diameter of the external thread and a second predetermined circumferential stress of less magnitude than the first stress is effected in the pipe wall at the largest diamter of thread engagement.
13. The invention of claim 12 wherein make-up of the connection comprises: first contact between the external thread and the internal thread at the smallest diameter of the external thread; at full make-up of the connection full engagement of the external threads is effected.
14. The invention of claim 1 further comprising:
the coupling being formed of a material having greater strength than the pipe material such that the combined wall strength through the connection effects a greater collapse resistance than does the pipe wall.
the coupling being formed of a material having greater strength than the pipe material such that the combined wall strength through the connection effects a greater collapse resistance than does the pipe wall.
15. The invention of claim 14 wherein the collapse resistance of the connection is sufficiently greater than the collapse resistance of the pipe wall such that neck-down and failure of the unthreaded pipe wall will occur before failure of the connection will occur, upon the application of increasing tension loads to an assembled connection.
16. The invention of claim 15 further comprising:
the pipe wall area at the last engaged thread being less than the nominal pipe wall area such that neck-down and failure are not able to occur at the last engaged thread because of said greater collapse resistance.
the pipe wall area at the last engaged thread being less than the nominal pipe wall area such that neck-down and failure are not able to occur at the last engaged thread because of said greater collapse resistance.
17. The combination of a connection for joints of oilwell tubing or the like comprising: a tubular coupling formed with tapered external threads thereon at each end for sealing engagement with tapered internal threads formed within the ends of the tubing joints to be connected, the connection being dimensioned and made of suitable material such that at full make-up, circumferential stresses within the small end of the external thread and within the large end of the internal thread are substantially at the same percentages of the yield stresses of the respective materials from which the joints and couplings are formed.
18. A high effeciency connection for joints of oilwell tubing or the like, comprising at least two joints joined together and forming: joints of pipe, each joint of pipe having a first end with no increase in wall thickness relative to the average pipe wall thickness and formed with tapered internal threads the joints each having a second end formed with tapered external threads dimensioned such that one such joint may be sealingly connected directly with another such joint; the threads being of sufficient length and taper such that the pipe wall strength of the first end in the area of the smallest diameter of thread engagement is at least three-fourths of the average pipe wall strength of the joints of pipe.
19. The connection of claim 18 wherein: the second end is formed with a bore diameter through the external threads of smaller dimension than the average bore of the pipe.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000468610A CA1260983A (en) | 1984-11-26 | 1984-11-26 | Oilwell tubing connector |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000468610A CA1260983A (en) | 1984-11-26 | 1984-11-26 | Oilwell tubing connector |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1260983A true CA1260983A (en) | 1989-09-26 |
Family
ID=4129219
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000468610A Expired CA1260983A (en) | 1984-11-26 | 1984-11-26 | Oilwell tubing connector |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1260983A (en) |
-
1984
- 1984-11-26 CA CA000468610A patent/CA1260983A/en not_active Expired
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| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |