GB2400434A

GB2400434A - Wear detection of flexible conduit

Info

Publication number: GB2400434A
Application number: GB0307984A
Authority: GB
Inventors: Andrew Loveridge; Adrian Robert Bowles
Original assignee: Qinetiq Ltd
Current assignee: Qinetiq Ltd
Priority date: 2003-04-07
Filing date: 2003-04-07
Publication date: 2004-10-13
Also published as: WO2004090520A1; GB0307984D0

Abstract

A system for detecting wear in flexible articles such as pipes, conduits, hoses and wires. An optical fibre is embedded into the flexible article such that wear of the article results in the associated degradation of the optical fibre. The reduction in the transmission of light is thus used as an indicator of the wear of the article. The system can also be applied to the elongate rubber pipe section of a pinch valve.

Description

WEAR DETECTION

This invention relates to the field of wear detection and more specifically to the detection of wear in flexible articles such as pipes, conduits, hoses and wires.

Many systems and articles will experience wear during the course of their normal operation. For example, electrical insulation around a conductor can undergo wear to expose a live electrical wire. Also, fluid containing conduits can experience wear both externally (from the environment in which they are located) and internally (from, for example, abrasive fluids) that can potentially compromise the structural integrity of the conduit. Failure to detect wear can result in system failure, financial losses and a reduction in operational efficiency.

Many industrial processes use rubber hosing to transport fluids. In some instances the fluids are abrasive resulting in degradation of the internal surfaces of the hosing. Often it is impossible to see abrasion from an external inspection of the hosing and the first indication that something is wrong is when the hosing catastrophically fails. There are two ways in which the possibility of the hosing being breached can be minimised. Either the hosing can be replaced after a given length of time regardless of the level of wear or a wear detection system can be used.

The detection of wear can however be a time consuming task. For example, manual checking of a pipe can be difficult. It is therefore desirable to provide automated systems 2s for the detection of wear.

Examples of wear detection systems exist for industrial pinch valves. Pinch valves comprise a section of compliant (usually rubber) pipe located within a piping structure To close offthe valve the compliant material is constricted (or "pinched") to prevent fluid flow. Wear and plastic deformation therefore occurs as a result of repeated cycling of the valve and also potentially as a result of the abrasive effects of the fluids which are passing through the valve.

Current wear detection systems for pinch valves either utilise an embedded mesh of copper wires within the rubber structure and assume conducting properties of the fluid passing through the valve, or require the rubber to be doped to make it electrically conducting. The copper wires used in the first solution are ductile and are therefore prone to artificial failure. This first solution will only function with conducting fluids such as aqueous solutions and will not work for many oils and solvents. The second solution is incapable of distinguishing between general low levels of wear occurring over a substantial portion of the internal pipe surface and a high level of localised wear (e.g. a deep crack within the rubber structure). This therefore leads to the early replacement of lo valves with a tolerable level of general wear on the assumption that there is more serious localised wear It is therefore an object of the present invention to provide a wear detection system which mitigates the problems with prior art wear detection systems.

Accordingly this invention provides an apparatus for detecting wear within an elongated article comprising an optical fibre which in use is embedded in the article where wear is to be detected, the fibre being substantially parallel to the long axis of the elongate article along a substantial length of the article, light generating means which is optically coupled to a first end of the fibre and, light detection means which is optically coupled to a second end of the fibre The invention provides an optical fibre which is embedded in the article which will experience wear. In the case of a pipe structure the optical fibre will be embedded between the inner and outer surfaces of the pipe When wear reaches the fibre the fibre itself begins to wear, and the passage of light is impeded and the onset of wear can therefore be inferred. The use of optical fibres means that the wear detection apparatus is independent of the properties of either the article or, in the case of pipes, the fluids passing through the article.

The light detection means detects whether the passage of light through the fibre is impeded or not and communicates this information in some way, e.g by displaying it visually or by electronic communication to a control system.

Although the term "light" is used it should be appreciated that any electromagnetic radiation source could be used and that the wavelengths should not necessarily be limited to the visible part of the e/m spectrum. Conveniently however an inexpensive light emitting diode can be used as the light source and a photodiode can be used as the light detector. A simple electrical circuit can then indicate when wear occurs The orientation of the optical fibre within the article is important. For flexible articles such as the rubber pipe structure of a pinch valve a helical winding of the fibre throughout the elongate article would not be suitable. In the case of a pinch valve the pipe walls will lo have a relatively small radius of curvature when the pipe is in the closed position. This would place a helically wound fibre under a high degree of strain which could result in the fibre breaking and a false wear detection result.

In contrast if the fibre is substantially parallel to the long axis of the article then the high strain can be avoided. Conveniently if the fibre is wound such that it is not quite parallel to the axis of the article it will, given a suitable number of loops back and forth along the length of the elongate article, cover the entire structure.

Conveniently the fibre should be located close to a critical wear point For the case of pinch valves the fibre would be embedded just inside of the tube reinforcement. As wear abrades the inside of the valve the fibre will be broken before the reinforcement is breached and replacement of the valve can be effected before any failure ofthe article.

A further advantage of the fibre orientation is that the two ends of the optical fibre can be located at the same end of the elongate article. This would allow the light generating means and detection means to be located together Embodiments of the invention are described by way of example only with reference to the accompanying drawings in which Figure I shows a pinch valve sleeve having embedded therein an optical fibre in accordance with the present invention.

Turning to Figure 1 a pinch valve I comprises a flexible rubber pipe section 3 having end flanges 5. The flanges 5 are used to connect the valve into a piping structure (not shown). Embedded within the valve 1 is an optical fibre 7. The fibre 7 is wound back and forth through the valve 1 many times.

The fibre 7 is wound such that its two ends (9, 11) enter and exit the valve in close proximity to one another. This allows the light transmission and detection means to be located next to one another instead of at opposite ends of the valve (as per prior art solutions).

The fibre 7 is substantially parallel to the long axis of the pipe section 3 in the centre section of the valve.

Claims

1. An apparatus for detecting wear within an elongate article comprising an optical fibre which in use is embedded in the article where wear is to be detected, the fibre being substantially parallel to the long axis of the elongate article along a substantial length of the article, light generating means which is optically coupled to a first end of the fibre and light detection means which is optically coupled to a second end of the fibre.

2. An apparatus for detecting wear within an article as claimed in claim I wherein the lo light generating means is a light emitting diode and the light detection means is a photodiode

3. An apparatus for detecting wear within an article as claimed in claim I or 2 wherein the fibre is located within the article such that in use it is between a critical wear point and a surface of the article that is to wear

4. An apparatus as claimed in any preceding claim wherein the article is a pipe.

5. An apparatus as claimed in any preceding claim wherein the article is a hose.

6. An apparatus as claimed in any preceding claim wherein the article is a conduit

7. An apparatus as claimed in any preceding claim wherein the article is an electrical conductor.

8. An apparatus as claimed in any preceding claim wherein the article is a diaphragm valve.

9. A pinch valve comprising an elongate rubber pipe section and means for clamping the pipe section such that a fluid cannot pass through the valve wherein an optical fibre is embedded within the rubber pipe section and is operably coupled at a first end to a light source and operably coupled at a second end to a light detection means.