GB2147987A - Improvements to heat transfer apparatus and plates therefor - Google Patents

Abstract

For many years gaskets for heat transfer plates have been secured by adhesive. This entails a great deal of preparation work. Recently, e.g., see GB. 2028996-A, mechanical retention has been suggested as an alternative. It has now been found that adequate retention may also be achieved by locally applied adhesive in the gasket recess (4), thus greatly reducing the preparation. <IMAGE>

Description

SPECIFICATION Improvements to heat transfer apparatus and plates therefor This invention relates to plate heat transfer apparatus and to plates for such apparatus.

In such heat transfer apparatus heat is transferred between two thin, broad streams.

The stream may be both of liquid or one stream of liquid and one stream of vapour or two streams of vapour, or in some cases one or both streams may have mixed liquid and vapour phases. The streams are separated by plates assembled in a spaced face to face relationship to provide flow spaces between the adjacent faces of the plates. The boundaries of the flow spaces are enclosed and sealed by flexible or resilient gaskets surrounding the flow spaces between the adjacent faces and disposed between the flow spaces and entry and exit ports. The ports, in plate heat exchangers usually one at each corner of the plate, are similarly surrounded or part surrounded by gaskets.

Each gasket is normally of a one piece construction set within a pressed groove formed in the plate. The manufacture of the gasket is normally carried out in moulds, but according to the size of the plate or the manufacturing techniques used the gasket may be assembled from two or more smaller components. The gaskets are normally moulded of an elastomeric material.

Many types of gasket constructions have been used, but gaskets with parallel side walls, fitting in matching recesses have been commonly used for many years. These constructions do not provide metal to metal support between the plates immediately outside the gasket recess and more complex constructions have been devised and used in order to achieve this, with improved gasket retention in high pressure applications.

The sealing force against the fluid pressure in the flow space is obtained by compression of the gaskets in a direction normal to the plate surface and the resistance to gasket extrusion from the proper sealing position in the groove is normally enhanced by securing the gasket to the plate surface by the application of a system of adhesion. The use of a system of adhesion also provides retention of the gasket on the plate during handling and assembly and disassembly of the pack.

This system of adhesion is frequently complex and time consuming involving the application of an adhesive to both the gasket and the plate surface, and assembly of the two components together. According to the system which is adopted it may be necessary to prepare the mating surface of either component before assembly and it may be necessary to subject the assembled components to a process designed for curing the bond after assembly. This complexity is the more marked when the side walls of the gasket recess are neither parallel nor generally straight.

The foregoing description covers the initial manufacturing process. It is common practice that as the elastomeric gasket material hardens and deforms in use with the passage of time, the servicing of the plate heat exchanger at the user's factory requires the replacement of the gasket.

Removal of the oil gasket requires destruction of the adhesive bond and cleaning of the groove. Also, it is not always possible to subject the newly assembled gasket to the optimum process of the adhesion such as would be applied during initial manufacture by the supplier.

In view of the complexity of the conventional process for securing the gaskets by adhesion, various recent proposals have been made to use mechanical means for releasably attaching the gaskets to the plates. In this connection, reference may be made to UK patent specifications 2028996-A, 2071303-A and 2075656-A. The mechani cal attachment described in these and other similar proposals normally necessitates forming apertures in the plates, and this adds to the cost of the plates, while the provision of the protuberances on the gaskets also adds to the tool costs for the gaskets. Such mechanical attachment is intended primarily to provide retention of the gaskets on the plates during assembly and disassembly of the pack.Once the pack is under compression, the inter plate pressure is normally sufficient to hold the gaskets in position in their recesses and to prevent their extrusion out under internal pressure in the flow spaces, when allied to a proper choice of geometry for the recess and gasket.

It has now been ascertained that an adequate retention of the gasket in the recesses may be achieved by using adhesive locally applied at spaced positions in the recess.

There is reference in EP 0039229-A2 to the use of tabs for securing a gasket to a plate at points outside the gasket recess, and there is also reference to the use of adhesive for securing these tabs to the plates. However, in this case the gasket is not attached into the recess but at a distance therefrom and so may be free to lift out of the recess, which leads to the risk of distortion and damage to the gasket, with consequent failure thereof on compression of the pack of plates.

In accordance with one aspect of the present invention, there is provided a plate for plate heat transfer apparatus, the plate having a gasket recess and a gasket secured in place in the gasket recess by locally applied adhesive at spaced positions in the gasket recess.

In accordance with another aspect of the invention, there is provided a method of securing a gasket in a gasket recess of a heat transfer plate, comprising applying adhesive locally to spaced areas of the gasket recess and inserting the gasket in the recess to be secured by the adhesive.

By the use of only spaced localised application of the adhesive, the amount of preparation required is greatly reduced, both on initial installation and on gasket replacement.

Withe improvements in adhesive technology, the requirements for stringent preparation of the surfaces is likely to reduce, and this will lead to improved acceptability, from an economic point of view, of the use of adhesive as opposed to mechanical retention.

The localisation of the adhesive to achieve adequate retention is particularly attractive in this connection, since the minimum preparation required can be readily applied at a number of locations.

The invention also comprehends plate heat transfer apparatus comprising plates in accordance with the invention or assembled in accordance with the invention, as set forth above.

The invention will be further described by reference to the accompanying drawing of which the single figure is an elevation of a conventional heat exchanger plate showing possible locations for localised application of adhesive.

The drawing shows an outline of a heat exchanger plate in which the plate 1 has the usual entry and exit ports 2 adjacent the corners, and a central heat transfer area 3 surrounded by a recess 4 to accept a resilient gasket. It will be seen that the gasket recess 4 extends round the periphery of the heat transfer area 3 and two of the ports 2, and has extensions to provide isolation of the remaining two heat transfer ports. Between these two ports and the heat transfer area 3, there is an isolated area 5 which does not normally receive heat exchange medium, but which is vented by a gap 6 in the gasket recess for the removal of possible leaked material. It will thus be understood that the gasketing itself does not have a heavy sealing function along the lengths 7 and 9 which isolate the areas 5 from the ambient, and therefore, adhesive applied locally on part of these lengths will not interfere with the proper functioning of the gasket. It is appreciated that on the side shown at the right of the figure, some further localised adhesive application will be required, and obviously greater care will need to be exercised in applying this adhesive within the gasket recess 4 at spaced and localised areas.

Various modifications may be made within the scope of the invention.

Claims (5)

1. A plate for plate heat transfer apparatus, the plate having a gasket recess and a gasket secured in place in the gasket recess by locally applied adhesive at spaced positions in the gasket recess.

2. A plate as claimed in Claim 1, in which at least some of the adhesive is applied at positions where the gasket does not normally have a sealing function.

3. A plate for heat transfer apparatus substantially as hereinbefore described with reference to the accompanying drawing.

4. A method of securing a gasket in a gasket recess of a heat transfer plate, comprising applying adhesive locally to spaced areas of the gasket recess and inserting the gasket in the recess to be secured by the adhesive.

5. Plate heat transfer apparatus comprising plates as claimed in claims 1, 2 and 3, or plates having gaskets secured thereon by a method as claimed in claim 4.