Electric heating – Inductive heating – Metal working
Reexamination Certificate
2000-02-14
2001-09-11
Walberg, Teresa (Department: 3742)
Electric heating
Inductive heating
Metal working
C219S635000
Reexamination Certificate
active
06288373
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an apparatus for amorphous bonding of tubulars.
During the construction of oil and gas wells it is usual to connect a large number of tubulars. Conventionally this is effected by screw couplings. One of the disadvantages of this construction is that the couplings are prone to corrosion with the result that a whole string of tubulars may have to be replaced every few years, particularly in high temperature, high pressure wells containing corrosive vapours.
It has been suggested that the longevity of such tubulars could be greatly increased, perhaps up to 25 years, if the couplings could be dispensed with.
One proposal for dealing with this problem has been to weld tubulars together. However, this is extremely hazardous at the head of an oil or gas well. Furthermore, normal manual welding does not result in a homogeneous metallurgical structure and the corrosion problem remains.
A technique of joining metal components known as “amorphous bonding” has been successfully utilised in the automotive industry. The surfaces of the components to be joined are ground into parallism. A foil of a metal alloy is then placed between the components which are mechanically pressed together. The joint is then subjected to local heating by an induction heater. The resulting structure is nearly metallurgically homogeneous.
It will be appreciated that it would be extremely desirable to be able to join tubulars by amorphous bonding. However, the technical difficulties are daunting insofar as it is necessary to transfer a process suited to a precision engineering shop to an area where inflammable and often explosive gas mixtures are present and where the rigidity of an engineering shop floor is replaced by a drilling platform which may well be offshore and which may be in continuous motion in heavy seas and inclement weather.
It is observed that UK patent specification No. 540,519 discloses a welding device comprising a ring burner which is surrounded by an annular water cooling jacket to reduce explosion hazards during the welding process.
European patent application No. 157131 discloses a double chambered sealing system for welding pipe end which injects inert shield gas in radial and axial directions into unsealed areas around the welding zone to prevent air contamination of said zone.
European patent application No. 418606 discloses an amorphous bonding apparatus in which nitrogen shield gas is injected into a jacket surrounding the bonded tubular ends and also nitrogen gas is injected into the interior of the bonded tubulars to create a virtually oxygen free atmosphere in the region of the bond.
Although the known devices provide some protection against explosion hazards they do not provide sufficient protection in an hazardous environment at the head of an oil or gas well.
The present invention is primarily concerned with reducing the risk of explosion while the amorphous bonding is taking place.
SUMMARY OF THE INVENTION
According to the present invention there is provided an apparatus for amorphous bonding the ends of tubulars which are in substantial axial alignment and surrounded by a shield gas, said apparatus comprising a jacket which in use is placed around said adjacent tubular ends, said jacket having an inner skin which, in use, defines a sealed inner fluid space containing a heating element and shield gas, and an outer skin which surrounds the inner skin such that in use a sealed outer fluid space is defined between said inner and outer skin.
It is preferred that said jacket is formed by two parts which are slidably mounted on a support frame and which can be urged together to form said jacket and that the inner skin is provided with fluid communication means which allow in use fluid to flow in a controlled manner from the inner fluid space into the outer fluid space or vice versa.
In one embodiment the apparatus comprises means to introduce a shield gas into the inner fluid space and means to introduce water into the outer fluid space and the fluid communication means comprises a conduit which, in use, can convey said shield gas to within said outer fluid space at a selected depth between the water level in the outer fluid space so that a selected pressure difference is maintained between the inner and outer fluid spaces.
In an alternative embodiment the apparatus comprises an inlet pipe for introducing a shield gas into the outer fluid space, an orifice in the inner skin for allowing the shield gas to flow from the outer fluid space into the inner fluid space and an outlet pipe for allowing the shield gas out of the inner fluid space, wherein preferably pressure control means are provided which in use control the pressure in the inner and outer fluid space such that the pressure in the inner fluid space is higher than the ambient pressure and the pressure in the outer fluid space is higher than in the inner fluid space. In this manner a high pressure gas shield is created in the outer fluid space which prevents air to flow into the inner fluid space and hot shield gases to leak from the inner fluid space into the atmosphere.
Suitably the apparatus further comprises a packer which in use is inserted into the interior of the tubular ends that are bonded by the apparatus, which packer comprises an elongate mandrel having a resilient packer element adjacent each end thereof, means to enable an inert shield gas to be introduced into an end of said elongate mandrel and to leave said elongate mandrel between said resilient packer elements, and means to enable water to be introduced into said end of said elongate mandrel and to leave said elongate mandrel between said resilient packer elements.
It will be understood that the external double skin jacket and the internal packer provide an adequate protection against explosion hazards during the amorphous bonding process since they prevent explosive gases to reach the area of the heating element and the tubular ends heated thereby and also prevent hot shield gases or other fluids to escape into the surrounding atmosphere.
REFERENCES:
patent: 5975405 (1999-11-01), Tsuchiya et al.
patent: 6078031 (2000-06-01), Bliault et al.
patent: 6184493 (2001-02-01), Tsuchiya
Jahn Michael
Pietras Bernd-Georg
Shell Research Limited
Van Quang
Walberg Teresa
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