GB2304221A

GB2304221A - Leak detection apparatus

Info

Publication number: GB2304221A
Application number: GB9515976A
Authority: GB
Inventors: John Alexander Boudry; David Harry Atton; Brian Jeffery Dawson
Original assignee: Petrotechnik Ltd
Current assignee: Petrotechnik Ltd
Priority date: 1995-08-04
Filing date: 1995-08-04
Publication date: 1997-03-12
Anticipated expiration: 2015-08-04
Also published as: GB2304221B; GB9515976D0

Abstract

Apparatus for detecting interfacial leaks in secondary containment pipelines, particularly in fuel supply systems, comprises a container 12 which is in use connected to the lower end of an inclined secondary containment pipeline 6 by means of conduit such as a tube 16. The conduit communicates with the interslit space between the secondary containment pipeline 6 and the supply pipeline 3 which it surrounds, and in use directs liquid from that space into the container 12. The presence of liquid in the container can be sensed by detection means 18 which is operable to trigger an alarm 20. There is also provided a kit of parts for making such apparatus, and a fuel supply system in which a tank 1 is connected to a number of dispensing pumps 2 by corresponding inclined secondary pipelines, all of which are connected to a common container 12 of the detection apparatus via respective conduits.

Description

Title: Leak Detection Apparatus Field of the Invention This invention relates to apparatus for detecting a leak of liquid into an elongate space defined by a fluid supply pipe and a secondary containment pipe, and to a fuel supply system which includes such apparatus. The invention also relates to a kit of parts for such apparatus.

Backaround to the Invention In the Petro/Chemical industries, it is becoming increasingly widespread to use secondary containment of fluid supply pipelines. In particular, it is becoming common for petroleum forecourt installations to use secondary containment of the fuel supply pipelines which connect the dispensing pumps of the installation to one or more storage tanks and of inlet pipes through which the tanks are filled. Each fuel supply pipeline is contained within a respective secondary containment pipeline which is optionally sealed at its ends to the fuel supply pipeline. The secondary pipeline prevents leaks from the fuel supply pipeline from being discharged into the environment.

Known leak detection apparatuses for systems in which the secondary containment pipelines are sealed against fluid supply pipelines pressurise the interstitial spaces between the fuel supply pipes and the secondary containment pipes with air or an inert gas and monitor the pressure in each individual space.

Such types of detection apparatus are consequently complex and expensive.

Summarv of the Invention According to a first aspect of the invention, there is provided apparatus for detecting a leak of liquid into an elongate space defined by a fluid supply pipeline and an inclined secondary containment pipeline through which the fluid supply pipeline extends, the apparatus comprising a container, a conduit for directing liquid from a region of said space at the lower end of the secondary containment pipeline to the container, an alarm, and detection means operable to detect the presence of liquid in the container and to activate the alarm when such liquid is detected.

The apparatus can be used in fuel supply systems in which a secondary pipeline is sealed against a fuel supply pipe, the conduit extending between the container and an outlet in the secondary containment pipeline. The volume of the container is preferably such that only a relatively small amount of liquid has to enter the container for the alarm to be activated.

Where the secondary containment pipeline is sealed at its lower end against the fluid supply pipeline, the conduit is preferably adapted to be connected to an outlet at said end of said secondary containment pipeline.

Since liquid which leaks into said space will run towards the lowest part of the secondary containment pipeline and hence towards the conduit, any such leak will result in liquid accumulating in the container where it is detected by the detector. The apparatus thus provides a relatively simple, and therefore cost effective, means of monitoring the pipeline for leaks.

Where the apparatus is for use with a secondary containment pipeline which is not sealed against its fluid supply pipeline, the conduit preferably includes means, for example a funnel for collecting liquid from the secondary pipe.

As well as detecting leaks of liquid from the fluid supply pipeline, the apparatus can also detect liquid which has leaked into the space from outside the secondary pipeline as a result of damage to the latter.

Preferably, the conduit is one of a plurality of such conduits, each arranged to direct liquid from a respective space defined by a respective fluid supply pipeline and secondary containment pipeline, to the container.

This enables one container, and hence detection means, to be used to monitor a plurality of pipelines.

Conveniently, the conduit comprises a tube which is preferably flexible.

The flexibility of the tube facilitates the installation of the apparatus since it allows adjustment of the position of the container relative to the secondary containment pipeline.

Where the apparatus has a plurality of tubes, each for connecting the container to a respective secondary containment pipeline, each tube is preferably transparent or translucent to enable liquid in that tube to be visible from the outside.

Thus, when a leak is detected, an operator can identify the secondary containment pipe into which the leak has occurred, simply by looking at the tubes and seeing which one contains liquid.

Preferably, each tube is connected at one end to a respective inlet in the base of the container. Preferably, each inlet includes a respective upright tube which projects from the base of the container to prevent liquid in the container from exiting the container through any of the inlets, when the level of said liquid is below the tops of said upright tubes.

Alternatively or additionally, the apparatus includes non return valves, each associated with a respective connecting tube and arranged to allow liquid to travel through that tube into the container, but substantially to prevent the passage of liquid in the opposite direction.

The detection means may comprise a level sensor for detecting whether any liquid in the container has reached a predetermined level. Preferably, the sensor comprises a float level switch.

Such a sensor is cheap, simple and reliable.

Preferably, the container includes an outlet to enable liquid to be drained from the container. Thus, if a leak in a given secondary containment pipeline is detected, the accumulated liquid can be drained from the container, thus enabling the apparatus to monitor the remaining secondary containment pipelines for leaks after the fluid supply pipeline in the secondary containment pipeline in which the leak has occurred has been shut down.

Preferably, the outlet comprises a passage in the base of the container under drainage valve for selectively opening and closing the passage.

According to a second aspect of the inventIon, there is provided a liquid fuel supply system comprising a storage tank for liquid fuel dispensing apparatus connected to the tank by a pipeline assembly comprising a fuel supply pipeline and a secondary containment pipeline through which the fuel supply pipeline extends, both pipelines being inclined so that the lowest end of the pipeline assembly is the end adjacent the tank, the two pipelines defining an elongate space therebetween, wherein the system includes leak detection apparatus comprising a container, the lower region of which is situated below the pipeline assembly, a conduit for directing liquid from the lower end of the space to the container, an alarm, and liquid detection means responsive to the presence of liquid in the chamber, the detection means being operable to activate the alarm when said liquid is detected.

Preferably, the pipeline assembly is one of a plurality of such assemblies, each connecting the storage tank to a respective dispensing pump, and the conduit is one of a plurality of such conduits, each connecting a respective assembly to the container.

Preferably, each secondary pipeline is sealed at its ends to its respective fuel supply pipeline, in which case each secondary pipeline includes at its lower end an outlet connected to a respective conduit.

The invention also lies in a kit of parts for leak detection apparatus in accordance with the first aspect of the invention, the kit comprising a container, a conduit for conveying liquid from a pipeline assembly into the container, and detection means adapted to be mounted in the container and arranged to be connected to an alarm and to activate the alarm on detection of liquid in the container.

Preferably, the kit includes a plurality of conduits, and the container has a plurality of inlets, one for each respective conduit, to enable the apparatus to be used to monitor a plurality of pipeline assemblies.

Brief Description of the Drawings A fuel supply system and leak detection apparatus in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a diagrammatic, partially sectioned side view of the apparatus when connected to a plurality of fuel supply pipelines (only one of which is shown) of the fuel supply system for a garage forecourt; Figure 2 is a plan view of a component of the apparatus shown in Figure 1; Figure 3 is a sectional side view of that component taken along the line A - A of Figure 2; Figure 4 is a section along the line B - B of Figure 3; and Figure 5 shows the apparatus, connected to two fuel supply pipelines, mounted in position in the manhole chamber of a fuel storage tank.

Detailed Description With reference to Figure 1, leak detection apparatus according to the invention is incorporated into a fuel supply system in which a fuel storage tank 1, which may be located above ground but in this example is located below ground level, is connected to a dispensing pump 2 via a fuel supply pipeline 3 which forms part of a pipeline assembly 4. The assembly 4 also includes a secondary containment pipeline 6 which is coaxial with the pipeline 3 and which is sealed against the pipeline 3 at its end by means of termination fittings 8 and 10. The pipelines 3 and 6 are formed from polyethylene.

With reference to Figure 5, the tank 1 is situated in a pit which also contains a manhole chamber 5 just above the tank 1 into which the pipeline assembly 4 extends so that the termination fitting 10 is situated within the chamber. The fuel supply pipeline 3 extends beyond the end piece 10 and is connected to an outlet pipe 7 of the tank 1 in the chamber, by a connector 9.

The pipeline 3 also extends beyond the end piece 8 to an inlet for the pump 2 which inlet is situated at a position higher than the end piece 10, so that the pipeline assembly 4 is inclined, with the termination fitting 10 being the lowest point on the secondary containment pipeline 6.

The tank also supplies fuel to three other dispensing pumps (not shown) connected to the tank along pipeline assemblies which are the same as the assembly 4, and 211 of which are inclined and extend into the tank chamber in a similar fashion to the assembly 4. One such other assembly is shown at 11 in Figure 5. Features of the assembly 11 which correspond to those of the assembly 4 are denoted by the same reference numbers, followed by the symbol '.

The leak detection apparatus for the system comprises a container 12 which is connected to a monitoring outlet 14 in the termination fitting 10 by a flexible transparent capillary tube 16. Each of the other three pipeline assemblies is connected to the container 12 through a respective capillary tube. Thus, for example, the outlet 14' of the assembly 11 is connected to the container 12 by a capillary tube 17. The container 12 houses a float level switch 18 which is connected to an alarm unit 20 and which activates the alarm unit 20 when liquid in the container 12 reaches a predetermined level.

The container 12 is positioned in the tank chamber, in the attitude shown in Figures 1 and 5, with its lower region at a level lower than that of the termination fitting 10, and of the corresponding termination fittings of the other secondary containment pipes.

The container 12 is formed from polyethylene, and comprises a cylindrical body portion 22 which is closed at its top and bottom ends by end caps 24 and 26. The base of the cap 26 includes five equi-angularly spaced apertures 28, 30, 32, 34 and 36. A respective one of four rigid tubes 38, 40, 42 and 44 extends through each of the apertures 28, 30, 32 and 34, and is sealed against that aperture by means of a seal, for example 46, and firmly held in position by a respective nippled stem connector, for example 47. Each of the apertures 28, 30, 32, 34 and its respective tube 38, 40, 42 and 44 constitutes a respective inlet for the container. For the sake of clarity, the tubes 38 and 42 have been omitted from Figure 3. The container 12 may include further similar inlets 8 for connection to further secondary contained pipeline assemblies for supplying fuel to additional pumps.Furthermore, one of the inlets in the base of the container may be connected to a secondary contained fill pipe assembly through which the tank is filled.

The upright tubes extend into the container 12, with the tops of the tubes being at the same level which is lower than the level of each of the monitoring outiets for the pipe assemblies. The bottoms of the tubes extend beyond the apertures in the cap 26 and the respective capillary tube, for example 16 or 17, is connected to the bottom of each upright tube by means of an 8-lOmm wormdrive hoseclip, for example clips 48 and 50. The aperture 36 forms part of an outlet passage which can be selectively opened or closed by a drain valve 52.

The detector 18 comprises a liquid level float switch which is suspended from the top of the container 12 by a cable 54 which passes through an aperture 55 in the cap 24 and through an airtight cable gland 56 which seals the aperture 55. The float switch 18 is of the same type as known float switches for detecting interstitial liquid in double-skinned steel tanks used in other applications.

If an interstitial leak of liquid (i.e. a leak of liquid into the space between the fuel supply pipeline 3 and the secondary containment pipeline 6) occurs in the pipe assembly 4, the liquid will tend to flow towards the termination fitting 10, since the outlet 14 communicates with the space between the pipes 3 and 6, a substantial proportion of that liquid will exit the space through the outlet 14 and thus pass into the tube 16. The liquid will then travel through the tube 16 under the influence of gravity, and will be discharged into the container 12 through the upright tube 40 when there is a sufficient amount of liquid in the tube 16 to provide the head of pressure necessary for this to happen.

In fuel supply systems in which fuel in the supply pipelines is pressurised, the pressure applied to the fuel may also urge liquid along the tube 16 in the event of a leak from the fuel supply pipeline.

When the liquid accumulated in the container 12 reaches a predetermined level, the liquid level float switch 18 electrically activates the alarm unit 20, which can emit an audio or visual alarm signal. In a modified version of the system, the alarm unit 20 can also optionally shut down the supply of fuel to all of the fuel supply lines when a leak is detected.

The pipes 38, 40, 42 and 44 prevent leaked liquid flowing out of the container 12 through the capillary tubes (as long as the level of leaked liquid is below the top of the upright tubes) so that the only capillary tube which contains liquid will be the one connecting the container 12 to the pipeline assembly in which the leak has occurred.

Thus an engineer can then inspect the flexible capillary tubes leading to the container 12 to determine which of the capillary tubes has traces of liquid in it, and hence the capillary tube through which the leaked liquid has passed. this enables the operator to identify which of the pipeline assemblies is faulty.

Having identified the faulty pipeline assembly, the engineer can shut down the fuel supply pipeline of that assembly, drain any leaked fluid from the container 12 using the valve 52, and then reset the alarm so that the apparatus can continue to monitor the other pipeline assemblies, which can continue to supply fuel. The drained fluid can be analysed to determine whether it is fuel or another liquid (eg water) and hence whether the fuel supply pipeline or the secondary containment pipeline is faulty.

It will thus be appreciated that the container 12 acts as a monitoring reservoir for all of the pipeline assemblies so that only one float level sensor 18 is required to monitor leaks in any of the assemblies.

Although the container 12, in this example, is airtight, a modified version of the apparatus may use a ventilated container, depending on the type of fuel to be supplied from the tank to the dispensing pumps.

In another modification to the apparatus, non-return valves may be fitted to the base of the container 12 between each of the capillary tubes and the associated nippled stem connectors.

The non-return valves ensure that there is no flow of liquid from the container 12 into the tubes.

The invention also relates to other fluid supply systems which employ secondary containment.

Claims

1. Apparatus for detecting a leak of liquid into an elongate space defined by a fluid supply pipeline and an inclined secondary containment pipeline through which the fluid supply pipeline extends, the apparatus comprising a container, a conduit for directing liquid from a region of said space at the lower end of the secondary containment pipeline to the container, an alarm, and detection means operable to detect the presence of liquid in the container and to activate the alarm when such liquid is detected.

2. Apparatus according to claim 1 in which the apparatus is adapted for use with a fuel supply system in which a secondary pipeline is sealed against a fuel supply pipe, wherein the conduit extends between the container and an outlet in the secondary containment pipeline.

3. Apparatus according to claim 1 or claim 2 in which the volume of the container is such that only a relatively small amount of liquid has to enter the container for the alarm to be activated.

4. Apparatus according to claim 2, in which the conduit is preferably adapted to be connected to an outlet at said end of said secondary containment pipeline.

5. Apparatus according to any of the preceding claims, in which the conduit is one of a plurality of such conduits, each arranged to direct liquid from a space defined by a respective fluid supply pipeline and respective secondary containment pipeline, to the container.

6. Apparatus according to any of the preceding claims, in which the conduit comprises flexible tube.

7. Apparatus according to claim 6, when appended to claim 5, in which each tube is transparent or translucent to enable liquid in that tube to be seen.

8. Apparatus according to either of claims 6 and 7, in which each tube is connected at one end to a respective inlet in the base of the container, each inlet including a respective upright tube which projects from the base of the container to prevent liquid in the container from exiting the container through any of the inlets, when the level of said liquid is below the tops of said upright tubes.

9. Apparatus according to any of claims 6 to 8, in which the apparatus includes nonreturn valves, each associated with a respective connecting tube and arranged to allow liquid to travel through that tube into the container, but to prevent the passage of liquid in the opposite direction.

10. Apparatus according to any of the preceding claims, in which the detection means comprises a level sensor for detecting whether any liquid in the container has reached a predetermined level.

11. Apparatus according to claim 10, in which the sensor comprises a float level switch.

12. Apparatus according to any of the preceding claims, in which the container includes an outlet to enable liquid to be drained from the container.

13. Apparatus according to claim 12, in which the outlet comprises a passage in the base of the container and a drainage valve for selectively opening and closing the passage.

14. A liquid fuel supply system comprising a storage tank for liquid fuel; dispensing apparatus, connected to the tank by a pipeline assembly comprising a fuel supply pipeline and a secondary cotitainment pipeline through which the fuel supply pipeline extends, both pipelines being inclined so that the lowest end of the pipeline assembly is the'wend adjacent the tank, and the two pipelines defining an elongate space therebetween; leakdetection apparatus comprising a container, the lower region of which is situated below the pipeline assembly, a conduit for directing liquid from the lower end of the space to the container, an alarm, and liquid detection means responsive to the presence of liquid in the chamber, the detection means being operable to activate the alarm when said liquid is detected.

15. A system according to claim 14, in which the pipeline assembly is one of a plurality of such assemblies, each connecting the storage tank to a respective dispensing apparatus, and the conduit is one of a plurality of such conduits, each connecting a respective assembly to the container.

16. A system according to claim 15, in which each secondary pipeline is sealed at its ends to its respective fuel supply pipeline, each secondary pipeline including an outlet connected to a respective conduit.

17. A kit of parts for leak detection apparatus according to any of claims 1 to 13, the kit comprising a container, a conduit for conveying liquid from a pipeline assembly into the container, and detection means adapted to be mounted in the container and arranged to be connected to an alarm and to activate the alarm on detection of liquid in the container.

18. A kit according to claim 17 in which the kit includes a plurality of conduits, and the container has a plurality of inlets, one for each respective conduit, to enable the apparatus to be used to monitor a plurality of pipeline assemblies.