GB2153019A - Sealing arrangements for plate heat transfer apparatus - Google Patents

Abstract

In order to provide improved sealing and mechanical interrelationship between the gasket 4 and plate 1 of a heat transfer apparatus such as a plate heat exchanger or a plate evaporator, there is provided a recess 6 in the upper surface of a gasket which engages with the outer face of the gasket recess in the superjacent plate. This provides an essentially Y shaped gasket with improved sealing and lateral engagement. The invention is particularly applicable to arrangements in which the height or depth of the gasket recess is no greater than the width of the recess. One of the limbs of the Y may be of harder material than the remainder of the gasket (Fig. 4). <IMAGE>

Description

SPECIFICATION Sealing arrangements for plate heat transfer apparatus This invention relates to sealing arrangements for plate heat exchangers and evaporators, referred to collectively as plate heat transfer apparatus.

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

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.

Because of the need to manufacture plates in as few pressing operations as possible the designer has been constrained in the past to incorporate peripheral gasket grooves greater in width than in depth. A practical ratio may be 22 or 3 to 1 in order to restrict stresses to a level which avoids excessive thinning during forming.

Exploiting larger more accurate presses, improved pressing lubricants and investment in more sophisticated tools, one hit pressing is avoided so that the need to complete the gasket groove at the same time that all other parts are formed is removed. For example the inner groove wall may be formed first, followed in a later stage by the outer groove wall. With this different flow pattern of the blank material, and hence a different control over the stress pattern, the possibility of producing grooves with equality of width and depth, or even grooves of less width than depth may be considered.

This effective reduction in the width requirement for the gasket recess leads to possibilities in the saving of gasket material, the cost of which is not inconsiderable, and also to a saving in the overall dimension of the plate for a given heat exchange area.

Hitherto, the gaskets have been generally arranged to have single or double peaks to engage the lower face of the base of the gasket recess in the adjacent plate and to provide a sealing area which flattens and broads as the pack of plates is compressed.

In accordance with a first aspect of the invention, there is provided a gasket for a plate heat transfer apparatus, said gasket being formed with a base and side wall portions to fit snugly within a gasket recess of a heat transfer plate, and being also formed with an upper surface to engage an external surface of the gasket recess of an adjacent similar plate, in which the upper surface is formed with a recess dimensioned to receive the base of the gasket recess of the adjacent plate for sealing engagement therewith.

The invention is particularly applicable in cases where the gasket recess is narrower than its depth or height. For example if the proportions are such that the side walls are joined at the base by a continuously radiused portion, or at least by two corners of radius 'r' and a flat width no more than 'r', the gasket cross section can become effectively Y shaped.

The engagement of the base of a gasket recess in a recess in the gasket upper face offers hydraulic sealing across two oppositely facing radii, giving strength of support and gasket entrapment, gasket to plate location in the direction of both adjacent plates and resistance to lateral displacement. There is in effect an inner seal with a supplementary outer seal giving greater security against leakage In accordance with a second aspect of the invention there is provided a heat transfer plate having a gasket recess with a base and side walls, a gasket snugly received within the gasket recess and having an upper surface for engagement into the base of a gasket recess on an adjacent similar plate, in which the upper surface is formed with a recess dimensioned to receive the base of the gasket recess of the adjacent plate for sealing engagement therewith.

The gasket may have an extension, possibly of harder material, on its outer side to engage me mechanically between adjacent plates.

The gasket may also, or alternatively, have a series of projections engaging with interference in a series of apertures in the plate to mechanically retain the gasket in position on the plate.

In accordance with a third aspect of the invention, there is provided heat transfer apparatus comprising a pack of plates in accordance with the invention as set forth above.

The invention will be further described with reference to the accompanying drawings, in which: Figure 1 illustrates in elevation a typical form of heat transfer plate to which the invention may be applied.

Figure 2 is a section on the line X-X of Figure 1 through two adjacent plates and the intervening gasket; Figure 3 is a modified version of figure 2; and Figure 4 is a cross section of a modified form of gasket.

Referring first to Figure 1, there is shown in elevation a typical form of heat transfer plate, in this case a heat exchanger plate 1, having-duct forming wholes 2 for.the.supply and discharge of-media to and from a heat exchange zone 3 which-is boundedtbV gasketting 4. The plate itself can have any suitable configuration, and in particular the.

heat exchange zone. may: be.corrug-ated.

turning now two Figure.-2, it will be seen that: the gasket 4 is retained in a gasket recess 5 of the --plate-.1. The gasket recess 5 is much narrower than is conventional-owing to the use of a process- as above.described -in which the gasket recess is pressed in several steps thus enabling avoidance of:the design constraints imposed in-one hit pressing, owing to the risk of excesive thinning.

It will be seen:that the recess 5 and gasket 4 are such that-the-side-walls are joined at the base. by a continuous radiused portion, which forms the base..ln accordance with the present invention the upper face -of the gasket is provided with a recess -6.which snugly receives the. base portion, arcuate in this caste, of the gasket recess 5 in the superjacent plate.

The gasket is-thus basically of a Y Section.with one arm.of the-Y indicated at 4a, extending towards the flow space and the other arm 4b extending outwardly.

This arrangements offers- hydraulic sealing across-two oppositely facing radii. on the gasket.

The arrangement is.such that the hydraulic pressure acting on the-arm 4a tends to tighten the gasket against the plates.

-In the arrangement. of Figure 2,- the plates terminate immediately outside the gasket recesses-5, and--in the arrangement of-Figure 3, the plates are continued into a downturned edge 7.With such an arrangement, a gasket shape such as-shown in Figure. 4 may be used in which the arm 4b of.the gasket is provided with. an .extension-4c fitting into the spacebetween the two adjacent.plates.his extension 4c may. in fact be of harder material than the sealing portion of the gasket since its primary function is mechanical interlocking of.the. of the plates and gasket In addition to moulded gaskets. described-and shown in Figure 2, with a continuously radiused base or a base in which the flat width is no greater than the corner radius 'r' on either side, it is possible to use a gasket which is circular or oval in cross-section and which on closure of the plate pack becomes deformed into the rounded Y shown in Figure 2.

It is further envisaged that the gaskets may, if required, be mechanically secured within their gasket recesses-by means of a series of projections on the gasket extending through matching holes in the plate metal..Suitable location for such retaining projections and holes would be in the region of the arm 4b or extension 4c.

Various modifications may bemade within the scope of the invention.

Claims (13)

1 . A gasket for-a plate heat transfer apparatus, the said gasket being- formed with a base and side wall.-- portions to fit snugly within a. gasket recess of a heat transfer plate, and being also formed with an upper surface to engage an external surface of the gasket recess of sun adjacent similar plate, in which the upper surface is formed with a recess di mensioned to receive the base of the gasket recess - of-the adjacent plate. for sealing engagement there -with,- -

2. gasket claimed in claim 1, in which the gasket is arranged to fit in a recess-of a width no greater than its height..-

3. A gaskets claimed in claim 1 or 2, including an extension on the outer. side to engage mechani cally between adjacent plates

4. - -A gasket as claimed in claim 3, in which the -extension .is of a: harder material than the sealing portion of the gasket. - . -

5. A gasket-as-claimed in any of claims to 4, -comprising.a series of projections to engage in ap ertures mechanically. to retain thejgasket-in its re cess.

6. A gasket for a plate heat transfer-apparatus, - substantially as hereinbefore described with refer ence to the accompanying. drawings..

7. A heat transfer plate having a gasket recess with a baseand-side walls, a gasket snugly re ceived within -the gasket recess and having an up per surface for engagement with the base of a gasket recess on an adjacent-similar-plate, in which the.upper surface is formed with a recess dimen sioned to receive the base of a gasket recess of the adjacent plate for sealing engagement therewith.

8. A heat transfer plate as claimed in claim 7, in which the gasket recess is of a width no greater than its depth or-height.

9: A heat transfer plate as claimed in claim .7 or 8, in which the gasket has:an extension on the outer side to engage mechanicallyrbetween adja cent. plates.

10. A heat transfer plate as claimed in claim 9, in which the extension is of harder material than the-sealing portion. of the gasket.

11. A heat transfer plate as claimed in any of claims 7 to 10, in which the gasket has a series of projections engaging with interference in a series of apertures in the plate to mechanically retain the gasket in position on the plate. -

12. A heat transfer plate substantially as her einbefore described with reference to. the accom panying drawings.

13. Plate heat transfer apparatus comprising. a pack of plates in accordance with any of claims 7 to 12. -'