Patent Application
20050172472
The invention relates to tubular joints, especially of the type used for hydrocarbon or similar wells, in geothermics for example.
Such a joint can exist between two tubes of considerable length, or between a tube of considerable length and a sleeve. These joints are used in particular to assemble columns of casing tubes (“casings”) or production tubes (“tubings”). Considering the mechanical properties required, the casings and tubings are usually made from heat-treated steel.
The joints themselves must offer resistance to traction, compression, bending and sometimes twisting, and also to extreme differences in pressure in both directions between the inside and the outside. And they must even be impervious to gases, at least in certain circumstances. Threaded joints are particularly advantageous in this respect.
But it is currently intended to subject the tubes, in situ, to diametric expansion, with continuous plastic distortion. This offers various advantages, to which we shall return. Once again it is important for the joints to remain operational, following the plastic distortion by diametric expansion to which they are subjected as are the tubes. Also, it is desirable for the threaded joints to hold firm after plastic diametric expansion, retaining the bulk of the properties which give them their value, especially mechanical resistance under traction/compression, with or without excessive internal or external pressure, as well as impermeability.
As will be seen in detail later, traditional joints do not offer complete satisfaction: either they do not meet these demands, or they meet them randomly, but not repeatedly.
WO 02/01102 proposes a joint structure intended to resist plastic diametric expansion.
The present invention will improve the situation.
The invention concerns a method for making a high performance sealed tubular joint, in which, from a first tubular joint consisting of
According to a principal feature of the invention, when said radial expansion occurs, a first inclined shoulder fitting axially facing in the opposite direction to said axial stop surfaces and formed on the peripheral surface of the male lip radially facing outwards, and a first inclined shoulder fitting axially facing towards said axial stop surfaces and formed on the peripheral surface of the female receiving element facing radially inwards, undergo axial displacement relative to each other to come into sealed mutual contact with radial interference.
Here “sealed contact” means contact between two surfaces tightly pressed against each other in order to make a metal on metal seal.
Optional features of the invention, as additions or substitutes, are given hereunder:
The invention also relates to a first tubular joint usable for implementing the method as defined above, consisting of
The invention also relates to a high performance sealed tubular joint obtainable by means of the aforementioned method, consisting of
The figures below illustrate, non-exhaustively, the methods of producing the invention, the identical or similar elements being designated on all the figures by the same reference signs.
FIGS. 4 to 7 represent the threaded joint of
FIGS. 18 to 23 are similar views to
The drawings basically contain elements of a certain type. Therefore they may not only be used for a better understanding of the description, but also contribute to defining the invention, if necessary.
Reference is made here to the drilling of wells, for hydrocarbons or geothermics for example.
Traditionally, the top of a well is first of all drilled over a relatively small depth of some tens of metres using a tool with a wide diameter, in the order of 500 mm, for example, and is lined by means of a column of tubes of that diameter. The drilling diameter then decreases by steps to the bottom of the well which can be drilled with a much smaller diameter, in the order of 150 mm in the same example. Such a well is then lined by means of several columns of concentric tubes, each one sunk on completion of drilling at the corresponding diameter and all suspended from the surface; the tubes with the greatest diameter extend from the surface to some tens of metres in depth and the tubes with the smallest diameter extend from the surface to the bottom of the well, the depth of which can reach several thousands of metres. The space between the casings and the land is cemented, for example.
After the well is fully drilled and lined, a column of tubings can be sunk, in particular so that the hydrocarbons can be raised to the surface, i.e. actual operation of the well. It is understood that this column of tubings has an external diameter which is slightly less than the internal diameter of the column of casings.
Equipping a well therefore leads to a large number of tubes of different dimensions being used, most often assembled by means of threaded joints bearing in mind the advantages of this type of assembly. An attempt is made to make these tubes as slim as possible, so that casings with too great a diameters are not required near the surface. But adherence to the constraints and specifications applying to the threaded joints often leads to their being endowed with a thickness which is greater than that of the running portion of the tubes; which obliges the diametric progression between concentric columns to be increased, as one descends deep into the well.
The tubes are fitted together either by screwing the threaded ends of the tubes into each other (so-called integral joints), or using threaded sleeves fitting over their ends. The tubes are sunk successively after being screwed into the end of the tube or previous sleeve. Specification API 5 CT of the American Petroleum Institute (API) also defines tubular threaded joints between two tubes of considerable length (“integral-joint tubing”, “extreme-ligne casing”) as well as sleeved threaded assemblies comprising two threaded joints enabling two tubes of considerable length to be assembled using a sleeve. These API joints are sealed only by the adding of lubricant loaded with metal particles which fills the interstices between the threads.
Of course the connections between tubes (or between tubes and sleeves) must remain impermeable whatever the stresses the tubes undergo when being sunk into the well, and in operation, and within a wide limit of supported mass, since each joint at least partially supports the tubes situated beneath it. So the mechanical performance of threaded joints seems closely linked to their geometric properties.
In the standard threaded joints according to API, despite the use of lubricants loaded with particles there is still an outlet in which a liquid at high pressure can circulate because of the play existing between the surfaces not in contact. For a given load under traction, there is a liquid pressure threshold beyond which the combined stress of traction and pressure initially causes a leak on the API threaded joints which can cause disengagement of the threading of the male and female parts in contact.
In order to avoid this, the threaded joints and assemblies have been the subject of various improvements: for example patents FR 1489013, EP 0488912, U.S. Pat. No. 4,494,777 have aimed to produce tubular threaded joints called superior or “premium”, which are particularly impermeable due to certain extents of metal-metal impermeability radially interfering with each other and due to stop limits between male and female elements carefully arranged so as to guarantee a given range of interference between extents of impermeability.
As indicated, after sinking a tubular column into a well, it is expected that it will be subject to diametric expansion, with continuous plastic distortion. This is produced for example by means of an expander being forced inside the column: see patents or patent applications WO 93/25799, WO 98/00626, WO 99/06670, WO 99/35368, WO 00/61915, GB 2344606, GB 2348657. This offers very interesting potentialities.
It would then be possible to considerably decrease the number of tubes needed to equip a well, doing away with the tubes of greater diameter and greater thickness. As a result the cost of the well is reduced. It may even be envisaged that the well might be drilled directly with the column of casings, which would take on the role of boring rods.
It has turned out that producing threaded joints which retain their performance after expansion which may exceed 10%, or even reach 25%, is extremely delicate, all the more so as it must be reliable (all the joints must retain their strength) and stable under operating conditions.
Threaded assemblies resisting expansion are known via U.S. Pat. No. 5,924,745 and WO 98/42947. But these are a matter of assembling so-called EST (expandable slotting tubings) tubes, fitted with crossing lengthways slits, and subject to diametric expansion at the bottom of hydrocarbon walls (by inserting an expansion chuck into said tubes); widened, the slits permit a liquid outside the tube (hydrocarbon deriving from the deposit) to enter the tube to be raised to the surface. In this case, the impermeability of the assemblies is clearly of no importance and, being at the bottom of the well, they do not take such a large mechanical load.
In fact, the first proposals for plastic expansion of sealed tubular columns are based on welded joints (bundles of tubes fitted end-to-end beforehand by welding, uncoiled from the surface) or on friction tubes (“slips”). But such joints do not have the performance of threaded joints, particularly with regard to the combination of mechanical strength, impermeability under all operating conditions, and also the possibility of subsequently being dismantled/re-installed several times.
It has turned out that classic tubular threaded joints such as those according to patent U.S. Pat. No. 4,494,777 do not withstand plastic diametric expansion. After expansion on these joints the following is found:
The production of a tubular threaded joint which may be able to resist the expansion operation in the well and which may be impermeable to liquids even, if possible, to gases after the said expansion operation, has therefore been sought. It has also been sought that the threaded joint should be simple and economical to produce. In addition it has been sought that the threaded joint should possess good metallurgical properties in operation hence after expansion, especially that when in that state it should present sufficient elastic limit, so that it is devoid of fragility and should present good crack-resistant properties under stress from H2S.
Threaded joints having a male lip corresponding to a female receiving element are known (U.S. Pat. No. 4,611,838, U.S. Pat. No. 3,870,351, WO 99/08034, U.S. Pat. No. 6,047,997). It turns out that these known assemblies do not retain impermeability after plastic expansion, which is furthermore in no way envisaged for them.
A method of producing a metal-on-metal impermeability joint in the form of a finger adapted to that art is described in the aforementioned international application PCT/FR01/02005. However with this method, with the highest expansion rates it is found that the mechanical stresses sustained by the tubes when the expander is inserted disengage the finger from its receiving element, causing insufficient impermeability, even a complete lack of it, in the joints.
By way of explanation,
The joint is shown in
The second tube 12 as represented is a tube of considerable length. This second tube may, in a way which is not represented, be a sleeve furnished on one side with the female element 2 and on the other with a second female element which may or may not be symmetrical with the latter and screwed to a male element situated at the end of another tube of considerable length.
Only the male element 1 is represented in
It includes a male threaded element 3, conical with trapezoidal threads, and is extended towards its free end by an unthreaded part formed by a throat 21 and by a lip 5 and terminates with a ring shaped surface at the male end 9.
The throat 21 is a shallow U shape.
It starts immediately beyond the threading and its depth hg is less than the height of the threads in the threading 3. Such that the bottom of the throat reaches the foot of the first thread of the threading.
The width of the throat 1g is markedly equal to 4 times its depth hg.
Lip 5 presents:
Lip 5 therefore has an even thickness e1, markedly equal to half the thickness et of tube 11. It has a length 11 measured from the end of the throat as far as the perpendicularity of the surface 15 (defined below) markedly equal to 3 times the thickness of lip e1.
The male end surface 9 forms a rebate. This rebate consists of a male ring shaped transverse surface 15 and a ring shaped tongue 13 projecting axially, adjacent to the transverse surface 15. The male transverse surface 15 is situated at the side of the rebate facing towards the interior of the threaded joint.
The external peripheral surface of the tongue 13 is within the extension of the surface 7 of the lip whereas its internal peripheral surface 17 is cylindrical, for example.
The radial thickness of the tongue 13 is markedly identical to that of the transverse surface 15 whereas the height of the tongue (or its axial projection) is markedly equal to the radial thickness of that same tongue. It may also be equal to 1.5 times that radial thickness so that it holds the free end of the tongue during expansion better,
The female element 2 alone is represented in
Starting from the free end of the female element, it consists of female threading 4 with trapezoidal threads matching the male threading 3 and then a non-threaded part 6. This non-threaded part 6 forms a receiving element to correspond and coincide with the lip 5 of the male element 1.
The female receiving element 6 presents a peripheral surface 8 facing towards the inside, cylindrical in shape, connected on one side to the female threading 4 and on the other via a female shoulder fitting 10 to the cylindrical internal peripheral surface 20 of the second tube 12.
In general, the diameter of the peripheral surface 8 of the receiving element is very slightly larger in diameter than the external peripheral surface 7 of the male lip 5. In this way, the surfaces 7 and 8 can slide into each other with little clearance when screwing the male element into the female element, for example with clearance of 0.2 mm. The advantage of such sliding action will be explained further on.
The female shoulder fitting presents a ring shaped shoulder fitting surface 10 which is arranged in a markedly corresponding manner and is markedly similar in shape to that of the male end 9. The surface 10 forms a rebate comprising a female transverse ring shaped surface 16 and a ring shaped groove 14 adjacent to the transverse surface 16.
The female transverse surface 16 is situated beside the rebate facing towards the interior of the threaded joint.
The wall 18 of the groove 14 adjacent to the transverse surface 16 is cylindrical for example and can be connected to the latter by means of a chamfer or rounding. The opposite wall of the groove is in the extension of the peripheral surface 8. When screwing the threaded joint, the surface 17 of the tongue “rises” on the wall 18 of the groove until transverse free end 25 of the tongue reaches the bottom 24 of the groove 14. The axial height hr of the tongue 14 and the axial depth pr of the groove are such that the transverse surfaces 15 and 16 do not come into contact until further screwing has taken place. The slight clearance between the cylindrical surfaces 7 and 8 and between the surfaces of the tongue and the groove that extends it enable the lubricant to be removed after screwing has taken place and therefore correct positioning of the lip 5 in relation to the receiving element 6.
FIGS. 4 to 7 explain the distortion phenomena which occur when diametric expansion in the order of 15% is carried out using an expander on tubes assembled by means of the threaded joints which have just been described and which enable an impermeable expanded joint to be eventually obtained.
Such distortion made on metal substances leads to plastic distortions in the metal.
Thus for example there is an increase from an external diameter of 139.7 mm (5.5 in.) on the second tube 12 upstream from the expansion and consequently in the part which is not yet distorted, to an external diameter of 157.5 mm (6.2 in.) on the first expanded tube 11 (at perpendicularity or downstream from the outlet cone 33 of the expander).
The plastic distortions generated increase the elasticity limit of the products: a tube originally having an elasticity limit of 310 Mpa (45 KSI) will thus increase to 380 MpA (55 KSI) after distortion.
Diametric expansion is produced in a known manner by means of an expander 30 (
The expander is for example biconic in shape with an inlet cone 31 on which the expansion takes place, a mid cylindrical part 32 and a conical outlet part 33.
All the surfaces of the parts of the expander are connected to each other by appropriate connection radii.
In particular WO 93/25800 discloses entry cone angles specially suited to diametric expansion of so-called EST tubes for the operation of hydrocarbon wells.
As tubes 11, 12 have a markedly continuous section, their ends do not present any particular problem when inserting the expander provided that the distortion capacity of the metal from which they are made is sufficient.
The problems to be solved derive from the fact that the threaded elements at the ends of the tubes are not as thick as those on the bodies of the tubes and vary in places, are more or less maintained and tend to distort differently between the male parts and the corresponding female parts.
If these differing distortions are overcome by using the threaded joint according to the invention, they enable a sealed threaded joint to be obtained after diametric expansion, not exhibiting any local redhibitory relief inside the internal peripheral surface of the tubes.
The process of expanding the threaded joint can be broken down into 4 phases which are the subject of FIGS. 4 to 7.
Although the expansion operation can be completely carried out in the opposite direction and lead to adequate results, the preferred method of distortion has been represented in which the expander moves from the male element 1 of the first tube 11 towards the female element 2 of the second tube 12.
a) The Phase of Expansion on the Cone of the Expander
Expansion is produced by the entry cone 31 of the expander 30 and
On
During said expansion phase, the reaction stresses to insertion of the expander 30 are progressively transferred from the first tube 11 to the second tube 12.
Due to these reaction stresses, the male lip 5 is axially compressed during said expansion phase by the ring shaped surface of the female shoulder fitting 10. Completion of the expansion phase corresponds to the free end of the male element reaching the end of the entry cone 31 of the expander.
b) Bending phase During this phase, the male lip is situated level with the central part 32 of the expander: see
i) Male Lip
The male lip 5 is subjected to bending moment in opposite directions on both its ends.
The surface of the male end 9 is in fact kept in position in the surface of the female shoulder fitting 10 because of the rebates with supports 15, 16 and because of the system of capturing the tongue 13/groove 14.
Capture of the rebates obliges the zone of the free end of the male lip 5 to follow the inclination of zone 22 of the full thickness of the female element beyond the shoulder fitting. This zone 22 is still in the course of expansion on the entry cone 31 of the expander and therefore creates a bending moment at that level.
The other end of the lip, on the male threading side 3, is no longer supported and on the contrary subjects the lip to bending moment opposite to that at the free end of the lip.
The bending moments in opposite directions at the two ends of the male lip cause the banana shaped curve of the male lip 5 as in
The state of axial compression of the male lip 5 on completion of the expansion phase, facilitates its curvature under the effect of the bending moments.
The throat 21 situated between the male lip 5 and the male threading 3 plays the role of a plastic coupling which accentuates the curvature of the male lip by limiting the width on which this curvature can take place.
However in this case care must be taken that the axial compression stresses on the male lip do not trigger buckling of the metal 23 beneath the throat. This buckling would result in projection of the metal beneath the throat in relation to the internal peripheral surface 19.
ii) Female Receiving Element
The same bending phenomenon occurs on the female receiving element.
Zone 22 of full thickness and relatively rigid in comparison with the relatively thin zones of the lip, undergo additional expansion when passing through the mid section, such that the internal diameter of zone 22 becomes greater than that of mid zone 32 of the expander. The additional expansion phenomenon is described in document WO 93/25800.
c) Straightening Phase
This phase, illustrated by
i) Female Receiving Element
The bending generated in the previous phase tends to be reduced to zero under the effect of the exertion and circumferential stresses, which generates a state of axial stress due to inverse bending in relation to the curvature, thus producing the straightening.
This bending moment caused by these stresses is proportional to the thickness of the material upstream from the straightening. When reaching the full thickness of tube 12 (zone 22), the bending moment is not sufficient to straighten the internal peripheral zone of the female receiving element which then tends to dip towards the axis of the product. This behaviour is manifested by a local reduction in the external diameter of the tube 12.
ii) Male Lip
As the female part straightens, the difference in axial bulk which was generated by the bending, decreases. The male lip 5 therefore progressively loses its state of compression. This continues with the separation of surfaces 15, 16 initially at the stop limit. This phenomenon is reinforced by “the dive” of the internal peripheral surface 8 of the female receiving element which produces the effect of opening the stop limits 15, 16.
The distortion into a banana curve imposed in the previous phase is retained.
d) Final state
The state of circumferential stresses caused by the expansion leads to reinforcement of the external peripheral surface 7 of the male lip by the internal surface 8 of the female receiving element. Self-reinforcement of the surfaces 7, 8 of the threaded joint in expanded state might then be referred to, which enables impermeability to be guaranteed. The male lip 5 does not dive towards the axis, as the radial offset imposed by the capture of the rebates 9, 10 has generated sufficient plastic distortions.
The elastic resilience of the elements of the threaded joint after insertion of the expander is negligible in relation to the plastic distortions implemented.
Radial reinforcement induces contact pressure of several tens of MPa, possibly more than 100 MPa, sufficient to guarantee impermeability under internal or external pressure on the threaded joint. The length of the reinforcement is sufficient over the entire periphery of the contact surfaces to guarantee stable impermeability between them.
Impermeability is furthermore necessary when expansion is produced by hydraulically thrusting the expander 30 under 10 to 30 MPa pressure, any leak in the already expanded joints hindering any further penetration of the expander into the column and therefore blocking the expansion process.
It will be noted that in its final state, it may very well occur that the tongue 13 no longer sits in the groove 14.
A male end surface 9 not captured in that female shoulder fitting 10 causes that end to dip during the straightening phase which sees the transverse surfaces 15 and 16 initially at the stop limit separate and an unacceptable projection of the lower end of the male lip inside the column then ensues. The column then no longer permits the equipment or tools to descend from a given spatial requirement.
Too great a clearance between peripheral surface 7 of the male lip 5 and peripheral surface 8 of the female receiving element on the threaded joint before expansion would not permit reinforcement of these surfaces on completion of the expansion operation.
Radial interference between these surfaces in the original state before expansion is likely to hamper the differential distortions (curving, straightening) between these surfaces during expansion operations, these differential distortions permitting reinforcement of these surfaces to take place on completion of the expansion operation. Thus it risks causing these surfaces to jam during screwing and wrong positioning of the elements with incorrect capture of surfaces 9 and 10 and thereby poor reinforcement of surfaces 7 and 8 after expansion.
In a preferred method of realisation, the form of ring shaped rebate with transverse surfaces 15, 16 and system of tongue 13/groove 14 enables the dipping of the male free end during expansion to be prevented. Other methods of producing embedded surfaces 9, 10 are possible in order to give the same result.
A very thin male lip 5, its thickness being less than one third of the thickness of the tubes 11, 12, does not enable an effective stop limit to be achieved on transverse surfaces 15, 16.
If the thickness e1 of the male lip 5 is on the other hand greater than 2/3 of the thickness of the tubes 11, 12, the thickness of tube 12 in the area of the female receiving element leads to a critical section of female threading 4 being too weak and consequently insufficient resistance to traction of the threadings.
The length/thickness ratio of the male lip 5 governs behaviour under compression and bending of lip 5.
A male lip 5 of length 11, less than its thickness, does not permit sufficient bending of the peripheral surface 7 of the male lip 5 and/or straightening of the peripheral surface 8 of the female receiving element.
A male lip 5 of length 11 4 times greater than its thickness e1 can cause buckling of the male lip and internal projection thereof on the threading side.
This effect is accentuated by the presence of a throat 21 between male threading 3 and male lip 5.
This is why it is preferable for the throat to have a depth limited to a thread height and length limited in relation to its depth.
A tongue 13 of insufficient radial thickness and axial height less than the radial thickness could not be sufficiently maintained during expansion.
Reference should be made to
The ring shaped lip 5 presents the peripheral surface 7 radially facing inwards. This peripheral surface 7 of the lip, starting from the male threading, comprises the throat 21 followed by a first cylindrical surface and then an inclined shoulder fitting 43 and a second cylindrical surface. The first cylindrical surface has a smaller diameter than the second cylindrical surface.
The receiving element 6 presents a peripheral surface 8 radially facing inwards. This peripheral surface 8 of the receiving element, starting from the female threading, comprises a first inclined shoulder fitting 42 followed by a second inclined shoulder fitting 41 to form a gill 40 with a cylindrical top between the two inclined shoulder fittings. The height of the gill is in the order of several tenths of a millimetre (for example, 0.4 mm).
Thus,
As the radial thickness of the tongue 13 is slightly less than that of the groove 14, the lower surfaces of them are not in mutual contact.
In a different geometric realisation of tongue 13, the latter does not have an axial size long enough to come into contact with the bottom of the groove 14. The screwing supercouple of
In the screwing phases D and E, the inclined shoulder fittings 41 of the receiving element and 43 of the lip are facing one another.
Advantageously, when assembling the joint, parts B and C enable it to be determined that the gill has been passed, indicating the last phase of screwing.
The surface of the male end 9 of the lip which forms a first axial stop surface comprises the tongue 13 which has rounded ring shaped edges.
The surface of the female shoulder fitting 10 of the receiving element which forms a second axial stop surface comprises the groove 14 and the female transverse ring shaped surface 16, the ring shaped edge connecting the groove to the ring shaped surface 16 being rounded. This rounded edge coincides with the rounded internal edge of the tongue 13 during a screwing phase requiring the insertion of the tongue 13 into the groove 14 between stages C and D.
In like manner, the inclined shoulder fitting 43 of the male lip connects by roundings, going towards the end of the lip, to a part of the peripheral surface radially facing outwards. This ring shaped rounding has a radius of curvature in the order of a few millimetres (5 mm for example). Preferably, the inclined shoulder fittings 41 and 42 of the receiving element should demarcate the gill. The top of said gill comprises a cylindrical surface demarcated on each side by a rounding. The ring shaped rounding of each of the inclined shoulder fittings 41 and 42 has a radius of curvature in the order of a few millimetre (5 mm and 9 mm respectively, for example).
These ring shaped roundings on the inclined shoulder fittings 41 and 42 of the receiving element coincide with the external rounded edge of the tongue 13 during the screwing phases B and C.
Thus, the ring shaped rounding of the inclined shoulder fitting 42 of the receiving element means that the risk of jamming when the tongue passes through can be reduced.
In the variant shown in
In this same variant, the peripheral surface 7 of the lip radially facing outwards comprises a cylindrical part 47 placed between the first inclined shoulder fitting 43 and the first axial stop surface 9. The space between the bottom of the ribbing 44 and the cylindrical part 47 and the clearances permit proper drainage of the lubricant during screwing.
During expansion of the joint, the concave shape of the ribbing 44 impresses a corresponding convex shape on the peripheral surface 7 of the lip, which has its maximum diameter thus augmented in relation to that obtained with the configuration in
In an advantageous method of realising the invention, in the last phase of screwing the joint is suitable for expansion according to an expansion rate of between 10% and 25%, the preferred expansion rate being 15%.
In
The radial expansion in fact leads to axial distortion causing displacement relative to the inclined shoulder fitting 41 of the receiving element and to the inclined shoulder fitting 43 of the lip. The axial direction of the expansion is immaterial, the contact between inclined shoulder fittings 41 and 43 resulting either from the inclined shoulder fitting 41 of the receiving element moving close to the inclined shoulder fitting 43 of the lip, or vice versa, the inclined shoulder fitting 43 of the lip moving close to the inclined shoulder fitting 41 of the receiving element.
In the case of an expansion rate of 15%, axial distance 1 is a few millimetres (2 mm, for example).
In
Thus, the radial distortions of the expansion have led to axial distortions of the lip 5 and the receiving element 6. The inclined shoulder fitting 43 of the lip comes into contact at least in a point F with the inclined shoulder fitting 41 of the receiving element, or vice versa. This sealed contact remains stable even under exertion. In the case of an expansion rate greater than the theoretical value chosen, the sealed contact is reinforced.
The ribbing impressed on the male lip has a greater local curvature which tends to favour contact between the tongue 13 and the flank 18 of the groove 14. This contact enables the behaviour of the lip to be locked in and stabilised under the pressure, especially internal, of a liquid.
The female element 2 of the first tubular joint represented in
As an example, for a tubular joint of external diameter 193.7 mm (7.625 in.) the profile of the ribbing 44 can have a radius of curvature of 6.31 mm, a width of 6.76 mm and a depth in the order of a few tenths of a mm.
When the expander is inserted, because of the radial stress sustained by the male lip, the part of the cylindrical surface 51 which is facing the ribbing 44 bulges to enter the free space demarcated thereby. Thus a shoulder fitting 52 is formed on the peripheral surface 7, connected to the shoulder fitting 41 defined by the flank of the ribbing 44. In the same way as the shoulder fittings 41 and 43 in
In the first tubular joint partially represented in
The profile of the ribbing is for example identical to that described in respect of
During radial expansion, a shoulder fitting 52 is formed on the male shoulder fitting in the manner described in respect of
The male lip represented in
However, the diameter of the part of surface 62 is greater than that of the part of surface 47, which eliminates the risks of these surfaces jamming during screwing.
For example, for a first tubular joint with an external diameter of 152.4 mm (6 in.) the profile of the ribbing 44 can present a radius of curvature of 10.4 mm, centred at 3.7 mm from the end face 25 of the tongue 13, and an axial length of 4.9 mm, the maximum depth of the ribbing being 0.445 mm in relation to the part of the surface 61 and 0.19 mm in relation to the part of the surface 62, the difference in diameter between these two parts of surface therefore being 0.51 mm.
During radial expansion, alongside pre-existing shoulder fitting 43, a shoulder fitting 63 forms on zones 43 and 47 of the peripheral surface 7 of the male lip, as described in connection with
The ribbing impresses greater local curvature on the male lip which tends to favour contact between the tongue 13 and the flank 18 of the groove 14. This contact enables the behaviour of the lip to be locked and stabilised under the pressure, especially internal pressure, of a liquid.
In the methods of realisation in
When manufacturing the initial tubular joint, it can be an advantage to apply, on one and/or other of the surfaces intended to come into sealed mutual contact, a layer of ductile material as described in the patent application No. 0200053 of 3 Jan. 2002. This ductile layer enables the roughness of the metals used for the male element 1 and the female element 2, to be overcome. The contact zone after expansion is increased between the inclined shoulder fitting of the lip and the inclined shoulder fitting of the receiving element.
As it is known, to avoid asymmetry when producing threadings and consequently a reduction in the mechanical strength of the joints, due to the fact that the respective external and internal diameters of the tubes are not concentric when they leave the manufacturing process before threading, prior to the threading operation an expansion of the external diameter can be carried out from the free end of the female element and extending over all or part of the length of threading to be produced.
Similarly, it is possible to reduce the internal diameter close to the end of the male element by a contraction carried out before machining.
Expansion and contraction can be carried out with a constant diameter, or with an increasing diameter for the female element, decreasing for the male element, in the direction of the outer end.
| Number | Date | Country | Kind |
|---|---|---|---|
| 02/00055 | Jan 2002 | FR | national |
| 02/03842 | Mar 2002 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR02/04546 | 12/24/2002 | WO |
