GB2245977A

GB2245977A - Device and process for detecting leaks on components containing or carrying a flowing medium

Info

Publication number: GB2245977A
Application number: GB9111522A
Authority: GB
Inventors: Guenter Serwatsky
Original assignee: Wrede & Niedecken Verwaltung
Current assignee: Wrede & Niedecken Verwaltung
Priority date: 1990-07-07
Filing date: 1991-05-29
Publication date: 1992-01-15
Also published as: DE4021664A1; GB9111522D0; NO912412L; NO912412D0; CA2043837A1

Abstract

A device for determining leaks on an insulated component 1 containing or carrying a flowing medium, wherein the component is surrounded by an insulation 2, and the insulation by an outer jacket 3, is designed such that the component 1 and the outer jacket 3 are electrically conducting and are connected as a capacitor such that they form the electrodes of the capacitor, and the insulation 2 acts as a dielectric whose properties change when contaminated by fluid leaking from the component 1. The component 1 may act as a conductor in a reflectometer so that the location of a leak can be established from the travel time of an applied high-frequency signal. <IMAGE>

Description

Device and Process for Detecting Leaks on Isolated Components Containing

or carrying a Flowing medium Specification

The present invention pertains to a device and a process for detecting leaks on isolated components containing or carrying flowing media.

Components of this type, on which leaks or corrosion are to be detected, have been known from the most different areas. Such a component may be, e. g., a heat- or sound-insulated container, in which a medium is stationarily stored. However, the component might also be a heat- and/or soundinsulated pipeline or a pipeline section, as used, e.g., in the chemical industry or refineries for 2 conveying gases or liquids.

A process and a device of this class have been known from West German Patent Specification No. DEPS 39,04,894. To detect leaks and/or corrosion, an electrical conductor, which undergoes corrosion as readily as possible, and whose electrical resistance is continuously monitored, extends at a predetermined distance from the component to be monitored for leak or corrosion. In the case of a leak from the component, e.g., when a liquid is being discharged, this conductor will undergo corrosion, as a consequence of which its electrical resistance will change. This change in resistance is used as an indicator of leakage.

As is apparent from the above description, the corrosion of the electrical conductor takes place only with a time delay, i.e., after beginning of the leakage. Consequently, it may happen under certain conditions that a considerable amount of the medium present or flowing in the component will have been discharged, may have penetrated into the insulation, and even have damaged the outer jacket by this point in time. In addition, the electrical conductor in the prior-art device must be replaced once it has corroded because of a leak.

3 Therefore, the basic task of the present invention is to further improve a device of the above-described class such that leakage of a component containing or carrying a flowing medium will be able to be detected immediately after the onset of leakage, with simple technical means. A corresponding process shall be specified as well.

The device according to the present invention accomplishes the abovedescribed task by the characteristics of patent claim 1. The corresponding process is described by the characteristics of claim 5.

Thus, the component and the outer jacket, which always extend at spaced locations from one another due to insulation, are electrically conducting and are connected as a capacitor such that they form the electrodes of the capacitor, and the insulation acts as a dielectric between the electrodes of the capacitor.

The present invention is based on the discovery that the change in the capacitance of a capacitor which is brought about by an effect on a dielectric located between the capacitor electrodes, can be used to determine leaks on insulated components surrounded by a (usually metallic) outer jacket. At the onset of a leak, the medium being discharged 1 is 4 causes an immediate change in the dielectric constant of the insulation, so that the leak can be immediately indicated by a corresponding change in capacity. It is only necessary to avoid electrical contact between the component and the outer jacket, i.e., the electrodes of the capacitor. However, this is already given in the prior-art, insulated pipelines and containers, so that the present invention can be realized with very simple means even in existing plants.

The insulation usually consists, if it is heat or cold insulation, of, e. g., a fibrous material, such as glass wool or rock wool. These insulating materials are nonconductors, so that they are well suited for the application according to the present invention.

The capacitor formed by the surface of the component and the internal surface of the outer jacket should be operated only with a low voltage and a weak current, especially if the component is accessible to operators. As a result of this, the risk of injury due to coming into contact with the device is eliminated, or additional electrical insulation of the device is no longer necessary, albeit possible.

In the case of monitoring a pipeline or a pipeline system in a refinery, the component is designed as a gas- or liquid-carrying pipeline. The insulation now surrounds the pipeline, and the outer jacket the insulation continuously. The pipeline and the outer jacket consist of, e. g., metal.

If leaks occur in such a case, i.e., when carrying a gas or a liquid, the change in the dielectric constant may be have two causes. On one hand, due to its presence, the gas or liquid may cause a change in the dielectric constant of the insulation in absorbing the gas or liquid. on the other hand, especially in the case of corrosive gases or liquids, a reaction with the material of the insulation may take place, so that the dielectric constant will change because of the material properties being newly established.

In order to make it possible to determine the exact location of the leak, especially in long pipelines, it is suggested in an advantageous embodiment of the present invention to design the component, i.e., for example, the pipeline, as an electrical conductor of a reflectometer, and to use, e.g., the component of the internal conductor of a coaxial cable. A preferably high-frequency signal is sent to the conductor, and the location of a leak 6 can be determined from the travel time of the signal. Such detectors have been known for a long time, but they are used for other purposes.

The above description of the device according to the present invention already includes the leak detection process according to the present invention.

The capacitance of the capacitor, which is predetermined by the surface of the electrodes, the distance between the electrodes and the dielectric constant of the dielectric (the insulation), is being determined or monitored continuously here. I the dielectric constant changes at the time of onset of a leak, the capacitance of the capacitor will change. Thus, this indicates a case of leakage practically without delay.

Via the component, which is connected as an electrical conductor of a reflectometer with a preferably high-frequency electrical signal, it is also possible to determine at the same time the location of the leak from the travel time of the signal.

Advantageous embodiments of the present invention are described by the characteristics of the subclaims as well as the other application documents.

7 The single figure shows a schematic representation of an embodiment of the device according to the present invention, in which the component is designed as a pipeline. The Figure shows a pipeline 1, around which an insulation 2 made from rock wool extends concentrically, and said insulation is covered on the outside by a jacket 3, which protects said insulation 2 especially from atmospheric effects.

According to the present invention, said pipeline 1 and said jacket 2 are electrically conducting and are connected as a capacitor, such that they form its capacitor electrodes. Said insulation 2 acts as a dielectric between the capacitor electrodes or between said pipeline 1 and said jacket 3.

In order for said pipeline 1 and said jacket 3 to be able to operate as capacitor electrodes, it is necessary for them to be connected, as a capacitor, in the known manner, to a power source, which is not represented here for clarity's sake. To eliminate the need for additional insulation of the jacket for the protection of operators, the capacitor is operated with a low voltage and a weak current.

8 If leakage (e.g., due to corrosion) occurs in the area of said pipeline 1, the medium (here: an acid) being carried by said pipeline 1 penetrates into said insulation 2 and changes its dielectric constant, as a result of which the capacitance of the capacitor will change immediately, and this change can be displayed and recorded.

Finally, it should be pointed out that the essence of the present invention -- detection of leaks on components containing or carrying flowing media -- can be realized in any type of component. The only requirement is that the component and the outer jacket should be electrically conducting and the insulation should be a dielectric.

9 9 is

Claims

1. Device for detecting leaks on insulated components (1) containing or carrying a flowing medium, wherein the component (1) is surrounded by an insulation (2), and the insulation (2) is surrounded by an outer jacket, characterized in that the component (1) and the outer jacket (3) are electrically conducting and are connected as a capacitor such that they form the electrodes of the capacitor, and the insulation (2) acts as the dielectric between the electrodes of the capacitor.

2. Device in accordance with claim 1, characterized in that the capacitor is operated with a low voltage and a weak current.

3. Device in accordance with claim 1, characterized in that the component (1) is designed as a gas- or liquidcarrying pipeline, and that the insulation (2) surrounds the pipeline, and the outer jacket (3) the insulation (3) continuously.

4. Device in accordance with claim 1, characterized in that the component (1) is an electrical conductor of a reflectometer, and a relatively highfrequency signal can applied to it, and that the location of a is leak can be determined from the travel time of the signal.

5. Process for determining leaks on insulated components containing or carrying a flowing medium, wherein the component is surrounded by an insulation, and the insulation by an outer jacket, especially for use in a device in accordance with claim 1, characterized by the following process steps:

the component and the outer jacket are electrically conducting, and are connected as a capacitor, so that they form the electrodes of the capacitor, the distance between the electrodes of the capacitor, and the insulation between the electrodes of the capacitor acts as the dielectric the capacitance of the capacitor, which is determined by the surface of the electrodes of the capacitor, the distance between the electrodes of the capacitor, and the dielectric constant of the dielectric, is continuously determined and monitored; when a leak occurs, flowing medium enters the insulation layer and causes a change in the dielectric constant, so that the capacitance of the capacitor will change; 1 the change in the capacitance of the capacitor indicates a leak of the component and is displayed.

6. Process in accordance with claim 5, characterized in that to locate the leak, a preferably high-frequency electrical signal can be applied to the component, which operates as an electrical conductor of a reflectometer, and the location of the leak is determined from the travel time of the signal.

Published 1991 at The Patent office. Concept House. Cardiff Road, Newport. Gwent NP9 I RE Further copies may be obtained frorn Sales Br-anch. Unit 6. Nine Mile Point. Cwrnfelinfach. Cross Keys, Newport, NP I 7HZ, Printed by Multiplex techniques ltd. St Mary Cray. Kent.