DETECTION OF LEAKS IN HEAT EXCHANGERS

Abstract

A method for the detection of leaks in a heat exchanger having discrete first and second fluid flow paths is disclosed. The method comprising the steps of introducing a contaminant fluid into the first flow path (13) and testing for the presence of the contaminant fluid in the second flow path (14), wherein the pressure in the second flow path (14) is maintained below atmospheric pressure. The pressure in the second flow path may be maintained, for example, at between 0.1 bar (110.sup.4 N/m 2) and 1 bar (110.sup.5 N/m 2) below atmospheric pressure. Apparatus for carrying out the method is also disclosed.

Claims

1. A method for the detection of leaks in a heat exchanger having discrete first and second fluid flow paths, the method comprising the steps of introducing a contaminant fluid into said first flow path and testing for the presence of said contaminant fluid in said second flow path, wherein the pressure in said second flow path is maintained below atmospheric pressure.

2-11. (canceled)

12. A method according to claim 1, wherein the pressure in said second flow path is maintained at between 0.1 bar (110.sup.4 N/m.sup.2) and 1 bar (110.sup.5 N/m.sup.2) below atmospheric pressure.

13. A method according to claim 1, wherein the pressure in said first flow path is maintained above atmospheric pressure.

14. A method according to claim 13, wherein the pressure in said first flow path is maintained at up to 3 bar (310.sup.5 N/m.sup.2) above atmospheric pressure.

15. A method according to claim 12, wherein the pressure in said first flow path is maintained above atmospheric pressure.

16. A method according to claim 15, wherein the pressure in said first flow path is maintained at up to 3 bar (310.sup.5 N/m.sup.2) above atmospheric pressure.

17. A method according to claim 1, wherein a dynamic flow of contaminant fluid is maintained in said first flow path.

18. A method according to claim 1, wherein a dynamic flow is maintained in said second flow path.

19. A method according to claim 1, wherein the contaminant fluid is selected from the group consisting of helium and hydrogen.

20. A method according to claim 19, wherein said contaminant fluid is present in a concentration of 5 to 10% by volume in a carrier gas.

21. A method according to claim 20, wherein the carrier gas comprises nitrogen.

22. Apparatus for detecting leaks in a heat exchanger having discrete first and second fluid flow paths, the apparatus comprising: a supply of contaminant fluid; means to connect said supply in fluid communication with said first flow path; a detector for indicating the presence of said contaminant fluid; and means to connect said detector in fluid communication with said second flow path; wherein the apparatus further comprises a vacuum pump and means to connect said pump in fluid communication with said second flow path, whereby, in use, a pressure below atmospheric pressure may be applied to said second flow path.

23. Apparatus according to claim 22, further comprising means to apply a pressure above atmospheric pressure to said contaminant fluid in said first flow path.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0013] The invention is hereinafter described in more detail by way of example only, with reference to the attached drawing, in which:

[0014] FIG. 1 is a schematic representation of an embodiment of apparatus according to the invention, for carrying out a method according to the invention.

DESCRIPTION OF EMBODIMENTS

[0015] In FIG. 1, a heat exchanger 1 is depicted diagrammatically, as is the possible presence of retained fluid 2 (typically water or another aqueous fluid). The FIGURE does not depict the detailed structural features of the heat exchanger itself, which are not crucial to the operation of the invention. The invention is suitable for use with any heat exchanger of the type possessing two discrete fluid flow paths. Suitable heat exchangers are, for example, of the plate type or tubular type, for instance as discussed and illustrated in EP 1,608,942.

[0016] The first (contaminant) flow path, indicated schematically at 13, is connected to a source of contaminant gas, illustrated in this embodiment as reservoir 9. This may, as discussed above, comprise helium of hydrogen as a minor constituent in a suitable carrier gas such as nitrogen. The contaminant gas passes through regulator valve 12 and its pressure may be monitored via pressure gauge 11. After passing through heat exchanger 1, the detector gas exits the apparatus through exhaust valve 10, for disposal or re-use.

[0017] The second (detection) flow path, indicated schematically at 14, is arranged to be in intimate thermal contact with first flow path 13 in a conventional heat exchanger arrangement (such as in a plate stack or tubular configuration). It is supplied via inlet valve 6 with a suitable gas such as air, which is drawn through the flow path by means of a reduced pressure induced by vacuum pump 3. A simple Venturi effect pump is suitable for this purpose but alternative pump types may be used if desired. The pressure in the second flow path 14 may be monitored by vacuum pressure gauge 5, to enable maintenance of the reduced pressure at a suitable level (for example, within the range 0.1 bar (110.sup.4 N/m.sup.2) to 1 bar (110.sup.5 N/m.sup.2) below atmospheric pressure).

[0018] Gas exiting second (detection) flow path 14 is sampled at sampling point 8 by detector 4, which is of conventional type, adapted to detect the presence of the specific detector gas supplied from reservoir 9 (for example, helium or hydrogen). The gas then exits via exhaust 7, for disposal (for example by release to the atmosphere).

Although the illustrated embodiment comprises a vacuum pump 3 and an exhaust pump 7, with the sampling point 8 and detector 4 positioned between the two, the structure and arrangement may readily be varied according to need. The volume and pressure of the gas exiting the second flow path is not critical to the operation of the invention, it simply being required that there be a flow towards the exhaust outlet, to draw any contaminant gas to the detector.

[0019] If the presence of contaminant gas is registered by detector 4, the presence of leakage between first and second flow paths 13 and 14 may be inferred, allowing the necessary remedial action to be taken. The lack of detection of contaminant gas will, similarly, indicate to a high degree of accuracy that the separation between first and second flow paths 13 and 14 is intact and that no significant leakage is occurring. As noted above, it has been found that the method and apparatus of the invention are capable of indicating the presence or absence of leakage with a significantly greater degree of reliability than the prior art methods.

[0020] While the invention has been described by reference to a particular embodiment, it will be apparent to those skilled in the art that various modifications can be made, within the scope of the appended claims.