GB2320760A

GB2320760A - Pipe leak monitoring system

Info

Publication number: GB2320760A
Application number: GB9627140A
Authority: GB
Inventors: John Glyndwr Burgess; Mark Anthony Burgess
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-12-24
Filing date: 1996-12-24
Publication date: 1998-07-01
Also published as: GB9627140D0

Abstract

Legs are detected in double containment pipework by sensing changes in pressure in the space between an inner fluid-carrying pipe 11 and an outer containment pipe 12. Two sensors 43,44 are set to respond at different levels to detect leaks in the inner and outer pipes. The sensor 43 responds when the pressure in the space between pipes 11 and 12 rises above a first preset level which is below the pressure of the fluid (21) in the inner pipe 11 and above the normal pressure of inert gas 22 in the space, and provides a signal to indicate a leak in inner pipe 11. The sensor 44 reponds when the pressure falls below a second preset level which is below the normal pressure of inert gas 22 and above the ambient pressure outside the pipe 12, to indicate that a leak has occurred in outer pipe 12. Actuation of the sensors may initiate automatic shut down. The location of the leak in the pipework system may be determined by isolating sections in turn.

Description

PIPE LEAK MONITORING SYSTEM This invention relates to a system for detecting leaks in fluid-carrying double containment pipework by means of pressure differential. The system can be used whether the fluid pressure is above or below the pressure in the environment surrounding the pipework. It is of particular importance for pipework carrying hazardous fluids at above atmospheric pressure.

Leak detection on pipe line installations is well known but in known systems pressure sensing is carried out by electrically operated sensing devices and the systems only indicate the presence of a leak somewhere in the system Detection is by means of contact of the leaking product with the sensor. The known systems can only detect leaks in the primary pipework.

Except for the gortex cable system, the detection devices are situated at the lowest point of the pipe run and it is some considerable time before a leak is detected. With known systems, it is not possible to establish in which section ofthe pipework the leak is situated.

According to the present invention a leak detection system for pipework comprising an inner fluid carrying pipe and an outer containment pipe wherein the pressure in the fluid carrying pipe is different from the pressure outside the containment pipe and the pressure in the space between the two pipes is intermediate between the pressure in the fluid carrying pipe and the pressure outside the containment pipe is characterised in that the pressure in the space between the two pipes is sensed by two sensors one of which responds when the pressure in the space between the two pipes rises or falls to a level which is closer to the pressure in the fluid carrying pipe and the other of which responds when the pressure in the space between the two pipes falls or rises to a level which is closer to the pressure outside the containment pipe.

A system according to this invention can establish if the primary pipework has a leak or if the containment pipework has a leak with complete safety when used on flammable products such as petrol, methanol, etc. and at the same time protect the inner pipework from corrosion and also establish what section of the pipework is affected by the leak.

A specific embodiment of the invention will now be described by way of an example with reference to accompanying drawings in which: Figures 1 and 2 show in cross section double containment pipework; Figure 3 shows a flange section of pipework fitted with a continuity loop; and Figure 4 shows pipework fitted with two pressure switches.

Pipework incorporating a system according to the invention comprises an inner pipe 11, Fig. 1, and an outer pipe 12. The inner pipe is typically 1 inch (25mm) in diameter and carries a hazardous fluid such as petrol or methanol 21, Fig 2. Around the pipe is an outer, containment, pipe 12 which is protected on the outside by a polythene coating 13. The pipe 12 is typically 2 inches (5Omm) in diameter. The space between the two pipes is charged with an inert gas (nitrogen) 22 at a pressure, which prevents corrosion of the outer surface of the inner pipe and the inner surface of the outer pipe. It also minimises the possiblity of fire in the event of a leak of petrol or methanol from the inner pipe. The inert gas 22 is at a pressure intermediate between the pressure of the fluid in the inner pipe 11 and the ambient pressure outside the outer pipe 12.

Sections of the inner pipe 11 are joined by flanges 31,32, Fig. 3, secured together by bohs 33.

The sections of outer pipe 12 are hemetically sealed to the respective flanges 31, 32 and an interruptable continuity loop 34 is provided so that in normal operation of the pipework the pressure between the both sections of inner and outer pipe is the same.

The outer pipe 12, is penetrated by two bores, 41, 42, Fig. 4, which communicate with pressure sensors 43, 44. The sensor 43 responds when the pressure in the space between the pipes 11 and 12 rises above a first preset level, which is below the pressure of the fluid 21 and above the normal pressure of the inert gas 22, and provides a signal to actuate an indication on a control panel that that a leak has occurred in the inner pipe 11. The sensor 44 responds when the pressure falls below a second preset level, which is below the normal pressure of the inert gas 22 and above the ambient pressure ouside the pipe 12, to actuate an indication on the control panel that a leak has occurred in the outer pipe 12. The responses ofthe sensors may be used alternatively or additionally to initiate safety shut down procedures automatically.

When a leak has been detected by the system, it can readily be located by isolating each of the sections of the pipe in turn and testing them for a leak manually. Each section is isolated by interrupting the continuity loops 34 at the ends of that section.

Claims

1. A leak detection system for pipework comprising an inner fluid carrying pipe and an outer containment pipe wherein the pressure in the fluid carrying pipe is different from the pressure outside the containment pipe and the pressure in the space between the two pipes is intermediate between the pressure in the fluid carrying pipe and the pressure outside the containment pipe, characterised in that the pressure in the space between the two pipes is sensed by two sensors one of which responds when the pressure in the space between the two pipes rises or falls to a level which is closer to the pressure in the fluid carrying pipe and the other ofwhich responds when the pressure in the space between the two pipes falls or rises to a level which is closer to the pressure outside the containment pipe.

2. A leak detection system according to claim 1, characterised in that the pressure outside the containment pipe is atmospheric pressure and the pressure ofthe in the fluid carrying pipe is above atmospheric pressure.

3. A leak detection system according to claim 1 or claim 2, characterised in that the fluid in the fluid carrying pipe is a hazardous fluid.

4. A leak detection system according to claim 3, characterised in that the fluid in the fluid carrying pipe is flammable.

5. A leak detection system according to any preceding claim, characterised in that an alarm is given in response to activation of one of the pressure sensors.

6. A leak detection system according to any preceding claim, characterised in that safety procedures are automatically initiated in response to activation of one of the pressures sensors.

7. A leak detection system according to any preceding claim, characterised in that pressure sensors operate without electricity contacting leaked fluid.

8. A leak detection system as claimed in any preceding claim, characterised in that the pipework comprises sections and the space between the inner and outer pipes in each section may be isolated from the space in adjacent sections in order to determine in which section a leak has occurred.

9. A leak detection system substantially as described with reference to the accompanying drawings.