GB2201219A

GB2201219A - A system to detect contents release from pipes, tanks or valves

Info

Publication number: GB2201219A
Application number: GB08703840A
Authority: GB
Inventors: James Wallace Pollitt
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-02-19
Filing date: 1987-02-19
Publication date: 1988-08-24
Also published as: GB8703840D0

Abstract

Occasionally water and electrically conducting liquids will leak from pipework, tanks or valves when corrosion, excess pressure, freezing or other events cause damage. The invention is a tape or cable incorporating one or more electrical conductors in proximity but separated by material which when dry is largely a nonconductor of electricity. The material is absorbant and porous to water and electrically conductive liquids so that when wetted an electrically conducting path is formed between the conductors, one of which may be the pipework, tank or valves. A simple electronics package connected to the conductors monitors the electrical properties of the tape and thereby establishes if the tape is wet or dry. Signals produced by the electronics package can then be used for warning or control purposes. <IMAGE>

Description

A SYSTEM TO DETECT CONTENTS RELEASE FROM PIPES AND OTHER FLUID CONTAINMENTS It is common experience that pipes and seals at joints connecting them can be split asunder by overpressure arising from various causes, such as hydraulic water-hammer or such as solidification of the contents during freezing. it is also common experience that poor assembly of soldered, brazed or compression joints correcting pipes to each other or to the mar:! components used in pipework will eventually laak.@orrosion of the walls of pipework or other fluid containments such as tanks and valves will also eventually lead to fluid release. Valves are also known to leak at body joints and at the seals around actuator shafts.

In many cases such leakage can cause considerable damage ar expense. his is particularly so in offices and private dwellings in which water leaking from frost damaged pipes can destroy parers; books furniture, electrical equipment and the fabric of the building itself.

With the trend towards greater thermal efficiency in modern buildings it is natural consequence that the water systems are increasingly threatened by frost damage.

The invention described below is a device which can be attached to vUlnerable fluid containments, such as pipework, which will signal if a leak occurs for whatever reason. The signal, produced by the device can be used to initiate one or more actIons. For example the signal could be used to alert personnel by raising an alarm and isolate the source of fluid supply automatically by means of a control valve.

The invention comprises one or more special fluid sensing tape(s) which is (are) wrapped around, or run parallel to, the various fluid containments from which leakage could occur. The taze(s) is (are) connected directly or by ordinary wires to one or more electronic control units which may be located at some distance from the anticIpated sources of leakage. The tape may be outsi2e lagging around fluid containments or between lagging and containment surfaces or in some embldiments of the invention may be incorporated within the lagging itself.

In one embodiment of the invention special tape is made from porous material in Which is incorporated one or more electrical conductors.

Normally the tape is wholly or partly dry and the electrical properties of the conductor(s) are at a value appropriate to this condition. When fluid leaks, some will reach the porous material and soak into it and so cause electrical properties of the conductors to be altered. The electronic control unit(s) to Which the tape conductors are connected monitor these changes in electrical properties and respond accordingly.

In one fort of sensing tape there are two conductors running parallel to each other and not touching and it is the electrical properties between the two which are monitored. In another form of sensing tape only one conductor is needed because the second conductor is the fluid pipework itself.

It is preferable that any potential differences appearing between conductors comprising the sensing tape are alternating so as to minimise the effects of electrolysis when the tape conductors are wetted by an electrically conducting liquid. It is also desirable that the voltages are small so that there is no risk of electrical shock to personnel inspecting or repairing larking pipework.

Figure 1 shows in sketch fom main features of one of many embodiments of the invention. Tho leak detecting tape shown in the drawing is shown disassembled at 2 to clarify the layer structure incorporating the two electrical conductors 3 and 4. When fixed together the composite tape is wrapped around or otherwise located so as to intercept leakages from fluid containments (refer Figure 2). The simplified electronic control unit drawn within the dotted lines is representative of a systen suitable for detecting conducting water.Electrical power from the mains supply passes via stepdown transformer 5 to, sa=yJ 10 volts. This voltage passes via resistors 6 and 7 and thus appears in full across the two sensing tape conductors.

provided -the sensing tape is dry and nonconducting. If the tape becomes partly or wholly -conducting current flow through resistors o and 7 will cause a fall of voltage at the junction of 6 and 7. This voltage reduction is detected in unit 3 which, in this example, causes switch contacts 9 and 10 to change in circuits connected to alarms and fluid shutoff and dump valves.

The tape will remain conducting until such time as the conducting fluid dries out. 11 is a protective device to limit voltage appearing across the sensing tape conductors, so ensuring no electrical shook hazard. 12 is a capacitor which with 7 comprises a filter to prevent radio frequency energy picked up by the sensing tape conductors affecting the sensing unit 3. Values of and 7 could be 10 kilohms and 1 kilohm respectively. and 12 could be 0.01 @fd. 11 could be rated at 20 volts breakdown.

Claims

1. A detector of water and electrically conductive liquids in the form of a continuous tape or cable which can be wrapped around, put below or otherwise located near possible sources of fluid leakage so that it will become wetted by intercepting such leakage.

2. A detector as claimed in Claim 1 wherein the tape or cable contains one or more electrical conductors separated from each other and the liquid containment by material which is absorbant and permeable to water and other conductive liquids and which is largely a nonconductor of electricity when dry.

3. A detector as claimed in Claim 2 wherein the abeorbant and permeable material separating conductor(s) and liauid contain ment also serves as thermal lagging of pipes and other fluid containments.

4. A detector as claimed in 1, 2 and 3 wherein an electronics package connected to the tape or cable discriminates whether the tape or cable is wet, dry or in an intermediate state.