Pipe joints or couplings – With casing – lining or protector – Lined
Patent
1997-09-29
1999-11-30
Nicholson, Eric K.
Pipe joints or couplings
With casing, lining or protector
Lined
2852881, 2853824, 2989014, F16L 914
Patent
active
059928972
DESCRIPTION:
BRIEF SUMMARY
The invention relates to joining lined pipe items, and to pipe fittings for use in such joining.
In particular the invention relates to joining pipes which have a lining, particularly a close-fit lining of polyethylene or other thermoplastic material. The pipes can be intended for use in conveying in particular for example liquid hydrocarbons containing carbon dioxide, hydrogen sulphide, methane or hydrocarbons. The liquid conveyed may be at a temperature of, for example, a value up to 160.degree. C. and may be at a pressure of, for example, a value up to 5000 pounds per square inch. The liquid conveyed may include exclusively, or in conjunction with the hydrocarbons, non-deaerated water; or brine. In general, the pipes can be intended to convey liquids which have a very deleterious effect on the material normally used for pipes. That material is usually metal, for example ferrous metal which may be steel or cast-iron. The pipes therefore are fitted with a liner of thermoplastic material to reduce the effect of the liquid conveyed upon the pipe.
Such lined pipes have to be joined, at intervals, in order to allow a long pipeline to be built.
At the ends of such pipelines the pipeline includes other pipelike items, such as valves. In this specification the expression "pipe item" means pipes and other pipelike items such as valves, for example.
It is an object of the present invention to provide a method of joining two metal pipe items; two metal pipe items joined by the method; and a metal pipe fitting for use in such a method, in which a said pipe item or a pipe fitting may be formed of ferrous metal, for example steel or cast-iron.
U.S. Pat. No. 5,009,737 (Lescaut--assigned to Atochem) describes a method of producing a pipeline arrangement comprising positioning pipes end-to-end with an internal covering terminating axially inwardly of the axial ends to define an uncovered inner wall section situated between adjacent longitudinal ends of said coverings, welding the ends of the pipes together, introducing a strip of fusible material radially inside of said uncovered wall section, and heating the strip while applying radially outwardly directed pressure to the strip to push the strip against said uncovered wall section to reduce the thickness of the strip and increase the longitudinal width of the strip to cause the strip to contact the adjacent ends of the coverings and completely cover the uncovered wall section and to weld the strip to the coverings.
In the example described in U.S. Pat. No. 5,009,737 each of two adjoining pipes has a covering composed of polyamide thermoplastic material. Each pipe adjacent its end is free from covering. The two adjacent ends of the pipes are welded together.
The strip is also composed of polyamide thermoplastic material and has an initial thickness of 6 mm and is 80 mm wide. The pipes adjacent their ends are heated by an induction heating unit to a temperature of 200.degree. C. while a pressure of 20 kPa is applied to the inner face of the strip. As soon as the temperature has reached 200.degree. C. heating is interrupted and forced cooling is applied until the temperature falls to 100.degree. C., when the pressure exerted on the strip is discontinued. As a result the strip is brought to a fused state and the strip is widened and the strip is welded to the ends of the coverings of the two pipes.
The pressure is applied to the strip by four blades movable radially by four hydraulic rams on a self-propelled carriage movable inside the pipes. This carriage is equipped with means for detecting the part of the pipes (in which the carriage is travelling) which is free from coverings. For example, a radioactive isotope may be provided or a mechanical feeler as the means.
Although the description mentions polyethylene as a covering material, it is not considered that U.S. Pat. No. 5,009,737 envisaged the use of a liner as a covering. A liner is a one-piece pipe-like member which is drawn into the steel pipe. By contrast, the covering described in U.S. Pat. No. 5,009,737 is a cov
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patent: 5326137 (1994-07-01), Lorenz et al.
patent: 5346261 (1994-09-01), Abbema
patent: 5348211 (1994-09-01), White et al.
patent: 5566984 (1996-10-01), Abbema et al.
patent: 5590914 (1997-01-01), Platner et al.
Cummings Robert James
Hill Tom
BG plc
Nicholson Eric K.
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