Pipe joints or couplings – Particular interface – Tapered
Reexamination Certificate
2001-06-20
2003-04-08
Browne, Lynne H. (Department: 3679)
Pipe joints or couplings
Particular interface
Tapered
C285S332400, C285S391000
Reexamination Certificate
active
06543816
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a threaded connector for pipes, more particularly for steel pipes which is intended for the petroleum and gas industry and for connecting pipes produced from this connector, of particular importance because of its tight seal against high external pressures.
The present invention relates to a threaded connector for pipes, more particularly for steel pipes which is intended for the petroleum and gas industry and for connecting pipes produced from this connector, of particular importance because of its tight seal against high external pressures.
DESCRIPTION OF THE RELATED ART
Pipe connectors used in the petroleum and gas industry are known in which the junction is constituted by an externally threaded male element which screws into an internally threaded female element, the two male and female threads mating with each other. Such connectors are used to produce extraction pipe strings or casing pipe strings for petroleum and gas wells.
Pipe connectors used in the petroleum and gas industry are known in which the junction is constituted by an externally threaded male element which screws into an internally threaded female element, the two male and female threads mating with each other. Such connectors are used to produce extraction pipe strings or casing pipe strings for petroleum and gas wells.
Depending on the severity of the conditions of the petroleum and gas exploitation wells, the basic structure of the connectors described above is completed in known manner by providing them with a variety of types of sealing means such as rings of synthetic material or metallic surfaces which bear on each other.
An example which can be cited is described in European patent EP 0 488 912 which describes a tapered threaded connector provided with a male tapered surface in the zone located after the male thread close to the free end of the male element, and in the corresponding zone of the female element with a corresponding female tapered surface, this pair of male and female surfaces bearing on each other when the connector is in the made up position forming an internal sealing surface against fluid circulating inside the pipes. The connector described in EP 488 912 is also provided with an abutment which enables the two male and female threaded elements to be precisely positioned with respect to each other when making up.
For certain applications, the connectors must resist and remain sealed both to the internal fluid pressure circulating in the pipe and to the external pressure existing outside the pipe. Such a seal is critical for the reliability of the connector when the external pressure is high (for example over 600 bars), whether the fluid concerned is a liquid or a gas or a mixture of the two. In this case, beyond a given pressure the internal sealing surface such as that described in EP 488 912 cannot resist fluid penetration which advances from the exterior to the interior along the thread and can then deform or even break the male lip on which said internal sealing surface is located, and it thus infiltrates into the interior of the pipe.
To overcome this problem, it has been proposed to provide the type of connector described in EP 0 488 912 with a sealing surface located close to the free end of the female element.
French patent FR 77 12851 thus describes a connector provided with an internal sealing surface close to the free end of the male element and with an external sealing surface close to the free end of the female element. It should be tight to internal and to external pressure. However, according to FR 77 12851, each of those two sealing surfaces is associated with an abutment, which renders the function and manufacture of the connector much more difficult. Abnormal deformations can occur when dimensional tolerances are not entirely adhered to or when the makeup torque is too high, which deformations can fundamentally modify the function of the two sealing surfaces and cause them to lose tightness as regards the fluid inside the pipe and the fluid outside the pipe.
Producing such a connector is expensive, firstly because of the machining tolerances required for it to function properly and secondly because of the quantity of material necessary to produce both an internal sealing surface and an external sealing surface, requiring the use of thicker pipes.
The prior art also discloses connectors in which the male and female elements comprise a tapered or straight threading constituted by two radially and axially offset independent threaded zones (such threaded zones can also be termed steps) which are provided with sealing surfaces.
Such is the case in EP 0 767 335 which describes a connector which comprises a tapered threading with two independent radially and axially offset threaded zones, with an internal sealing surface close to the free end of the male element and an external sealing surface close to the free end of the female element. However, because of the situation of the external sealing surface close to the free end of the female element, this sealing surface cannot resist very high pressures as there is not sufficient material at the end of the pipe to keep said surface rigid.
Further, EP 0 149 612 describes a connector which comprises a threading with two radially and axially offset independent threaded zones with different tapers between which a sealing surface is provided constituted by male and female surfaces in bearing contact during makeup, that connector also comprising an internal sealing surface close to the free end of the male element and an oblique abutment at the free end of the male element.
Because of the structure of the two radially and axially offset independent threaded zones, the connector of EP 0 149 612 requires relatively thick pipe walls and because of the corresponding cost and bulk, it is difficult to envisage it being produced in the form of a coupling.
BRIEF SUMMARY OF THE INVENTION
The present invention seeks to provide a threaded pipe connector which, while being tight to external pressure, does not have the disadvantages of the above connectors.
The present invention seeks to provide a threaded pipe connector which, while being tight to external pressure, does not have the disadvantages of the above connectors.
Thus a connector is sought which is tight at high external pressures while remaining tight to internal pressure and which is simple, robust and economical both as regards the quantity of material and the thickness of the pipes which are required, and as regards machining.
The term “robust” means a connector which can resist high pressures, for example of the order of 600 bars to 1500 bars, and which is easy to assemble on-site.
The production of a threaded pipe connector has also been sought, which connector differs as little as possible from connectors which already exist, where the threading is constituted by a single threaded zone in contrast to threaded connectors wherein the threading comprises two independent axially and radially offset threaded zones, and which can be produced from such connectors with a single threaded zone without modifying the structure of the assembly.
A connector which has a single sealing means which can be used both against internal pressure and against external pressure has also been sought.
The connector of the invention is intended for the production of pipelines or strings.
Its field of application is not limited to the petroleum and gas industry but extends to any application where the.same types of problems occur or can occur.
A non limiting example is geothermal liquid or vapour water extraction.
The connectors are produced from any metallic materials, for example steel or ferrous or non ferrous alloys in particular with the desired mechanical characteristics and with the corrosion strength required for the envisaged application.
The threaded pipe connector of the invention is of the type comprising a male element disposed at the end of a first pipe and a female element disposed at the end of a second pipe.
The male element compris
Bochna David E.
Browne Lynne H.
Vallourec Mannesmann Oil & Gas France
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