GB2324845A

GB2324845A - Pipeline joint for double-skinned pipes

Info

Publication number: GB2324845A
Application number: GB9708935A
Authority: GB
Inventors: Ross John Nairn Smith
Original assignee: Castrol Ltd
Current assignee: Castrol Ltd
Priority date: 1997-05-02
Filing date: 1997-05-02
Publication date: 1998-11-04
Also published as: GB9708935D0

Abstract

The joint, for positioning between two sections of double skinned pipeline comprising of an inner pipe 12 to contain a fluid at an elevated pressure and a sheathing pipe 14 defining a space to contain a second gaseous fluid, comprises a pair of flanges 2 and an interposable gasket 7 both having alignable central apertures 3, 9 and the flanges having circumferentially arranged outer apertures 6, the gasket having aligned slots 10.

Description

PIPELINE JOINT This invention relates to a joint intended to be positioned between two sections of double skinned pipeline.

Many fluids, such as fuels and hazardous chemicals, are required to be transported through double skinned piping which has a sheathing around the pipe carrying the fuel. The sheathing defines an annular space filled with a harmless gaseous fluid such as nitrogen. The gaseous fluid is maintained at a pressure which is greater or less than atmospheric but different from that in the fuel pipe. Monitoring of the pressure of the gaseous fluid by any suitable means, such as the provision of pressure transducers, can thus detect any failure of the system. For example, if the fuel is being transported at 20 psi, and the gas is maintained at 10 psi, detection of an increase in pressure means that there is a failure of the fuel pipe itself, while detection of a decrease in pressure means that there is failure of the protective sheathing.

Problems with this system are encountered when joining two sections together. It is necessary to provide additional piping linking the sections of sheathing, which piping is arranged to lie outside the actual joining flange arrangement for the fuel pipes themselves, or alternatively to weld both inner and outer pipe joints in situ. In particular when attempting to arrange such pipelines in restricted locations, this is difficult. Furthermore, when employing flanged joints the safety provision in the region of the flanged junctions is inadequate.

The present invention seeks to provide a solution to this problem.

According to the present invention we provide a joint intended to be positioned between two sections of double skinned pipeline, which pipeline sections each comprise an inner pipe to contain a first fluid at a first elevated pressure and a sheathing pipe defining an annular space to contain a second gaseous fluid at a second pressure less than the first elevated pressure, the joint comprising a pair of flanges and an interposable gasket, the flanges and gasket having alignable central apertures to allow through passage of the first fluid and the flanges further having circumferentially arranged vents for communicating at one face with the annular space containing the second fluid and at the opposite face with apertures through the gasket.

The invention further provides a double skinned pipeline assembly comprising at least one joint as defined above.

The flanges may be of any suitable rigid material resistant to the fluids being transported. They are suitably of diameter greater than that of the sections of double skinned pipeline to allow the flanges to be fastened by circumferentially arranged bolts. The vents preferably communicate with a continuous groove in that face of the flange which abuts the gasket and provides a detection space. The gasket, which may be of any suitable resilient material resistant to the fluids employed, preferably has apertures in the form of circumferentially arranged cut-outs which align with the grooves in the flanges.

The first fluid may be fuel or a hazardous chemical. The second gaseous fluid may be air and is preferably an inert gas such as nitrogen. Means are preferably provided to monitor the environment containing the second fluid suitably in the region of the continuous grooves. Changes in pressure in that environment may be monitored by provision of a pressure transducer or alternatively leakage from the inner pipe may be monitored by provision of a specific detector for the first fluid.

One form of the invention will now be described with reference to the accompanying drawing wherein Fig. 1 is a plan view of one flange of the joint.

Fig. 2 is a section of line X - X of Fig. 1 showing a fragment of double skinned pipeline in place; and Fig. 3 is a plan view of a gasket.

As shown in Fig. 1, each flange of the joint comprises a plate 2 having a central aperture 3, bolt holes 4 around its periphery and a continuous circular groove 5 providing a detection space in the base of which are a series of through vents 6 which extend through the flange.

As shown in Fig. 3 the gasket 7 has bolt holes 8 arranged to match the holes 4 of the flanges, a central aperture 9 which matches the apertures 3 of the flanges and cut-outs 10 which, when assembled, will abut the grooves 5 of the flanges.

Fig. 2 is a cross section of one flange, by showing the flange sealed against a double skinned pipeline having an inner primary pipe 12 sheathed by an outer pipe 14, providing secondary containment.

In use, a first fluid under pressure will pass through the joint through pipe sections 12 and through the apertures 3 and 9. Failure of the inner pipe and the joint in this region will result in leakage of fluid into the space 15 defined by the outer pipe 14, where the pressure will rise and be detected by suitable monitoring means. The protective gaseous fluid, at a pressure below that of the first fluid, will pass through space 15, vents 6 and cut-outs 10 in the gasket. Failure of outer pipe 14 or in that region of the joint will be picked up by a decrease in gaseous pressure.

It will be appreciated that the joint is of simple construction, avoiding the need for additional ducting for the gaseous fluid and maintains the protected environment in the region of the joint.

Claims

1. A joint intended to be positioned between two sections of double skinned pipeline, which pipeline sections each comprise an inner pipe to contain a first fluid at a first elevated pressure and a sheathing pipe defining an annular space to contain a second gaseous fluid at a second pressure less than the first elevated pressure, the joint comprising a pair of flanges and an interposable gasket, the flanges and gasket having alignable central apertures to allow through passage of the first fluid and the flanges further having circumferentially arranged vents for communicating at one face with the annular space containing the second fluid and at the opposite face with apertures through the gasket.

2. A joint according to claim 1 wherein the vents communicate with a continuous groove in that face of the flange which abuts the gasket.

3. A joint according to claim 2 wherein the gasket has aperture in the form of circumferentially arranged cut-outs which align with the grooves in the flanges.

4. A joint according to claims 1, 2 or 3 provided with means for monitoring the environment containing the second fluid.

5. A joint according to claim 4, wherein the monitoring means comprises a pressure transducer.

6. A joint according to claim 4, wherein the monitoring means comprises a detector for the first fluid.

7. A double skinned pipeline assembly comprising at least one joint as described in any one of claims 1 to 6.