Pipe joints or couplings – Molded joint – Sleeve
Patent
1991-04-01
1992-07-07
Trettel, Michael F.
Pipe joints or couplings
Molded joint
Sleeve
285 55, 285915, 285 21, F16L 4700, F16L 914
Patent
active
051271168
DESCRIPTION:
BRIEF SUMMARY
The invention relates to pipe joints.
The joint is of particular interest with regard to pipes of the kind having a liner and suitable particularly, though not exclusively, for conveying liquids or gases at pressures higher than that which the unsupported liner is capable of withstanding.
In a particular example of such an application, long lengths of steel pipe are made up by welding end-to-end stock lengths (e.g. 38 foot) of pipe of, say, 14-inch diameter (355 millimeter). This long length is lined with a liner of polyolefin material by pulling the liner through a die to reduce its diameter and pulling it through the pipe. Subsequently, the liner is allowed to revert towards its original size and in so doing it tightly engages the pipe wall. This procedure is repeated and the long lengths of lined pipe are joined end-to-end using the joint according to the invention. Further long lengths are joined to complete the pipeline.
The lengths of pipe are supported on scantlings, for example, and each pipe is pulled up to its neighbour by hydraulic jacks before the joint is effected. The scantlings allow the pipe to slide at this stage. Afterwards the scantlings may be secured to the pipeline.
According to the invention a joint for pipes, each of which contains a liner of polyolefin, comprises two pipe end portions spaced apart with their liners protruding from the end portions and joined by joining means, a shell interconnecting the pipe end portions, and grout in the space between the liners and the shell.
In one preferred embodiment the joining means comprises an electrofusion coupling.
In another preferred embodiment the joining means comprises flanges having seal means pulled together by bolts.
Embodiments of joint will now be described by way of example with reference to the accompanying drawings, in which:
FIG. 1 is a longitudinal section through the first embodiment of joint;
FIG. 2 is a scrap longitudinal section showing a modification of FIG. 1;
FIG. 3 is a longitudinal section through the second embodiment of joint;
FIG. 4 is a longitudinal section through test rig for an example of the joint;
FIG. 5 is a section on the line V--V shown in FIG. 4; and
FIGS. 6 and 7 are sectional side elevation views showing flanges for joining pipe liners in accordance with the invention.
In FIG. 1 there is shown a joint 10 comprising two pipe end portions 12, 14 spaced apart, with the liner 16, 18 within the pipes protruding at 17, 19 from the end portions 12, 14. The line 16, 18 is of medium-density polyethylene, for example, and the liners are joined by joining means in the form of a electrofusion coupling 20. This is a hollow body of polyethylene open at each end and having a heating element by which it can be heated and caused to fuse itself and the pipe to which it bonds.
The pipe end portions 12, 14 are interconnected by a shell 22 which is made up of two flanges 24, 26 secured by welding to the pipe end portions 12, 14, respectively, and a cylindrical shell wall 28 secured by welding to the flanges 24,26. The shell wall 28 has ports 30, 32 by means of which grout 34, such as epoxy or ordinary cement, for example, can be injected.
The pipes are nominally, for example, 14-inch (355 mm) in diameter and are of high pressure, steel construction with a pipe wall of three eights of an inch (9 mm) thick. The liner is relatively thin and is preferably of at least 8 mm thickness where the pipe is of 14-inch size. The pressure, which is sustained within the liner is, in this example, at least 350 psi. This joint is suitable however for use at much higher pressures.
The pressure in the liner is greater than the liner could withstand alone. However, the presence of the grout between the liner and the shell supports the liner and the pressure load is effectively transferred through the epoxy cement to the shell.
The individual stock lengths of pipe are joined by butt welding in the field to make up a long length of pipe which is then joined, using the joint of the present invention, to another long length or to several long
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British Gas plc
Trettel Michael F.
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