CA1086301A

CA1086301A - Gasket for use in plate type heat exchanger

Info

Publication number: CA1086301A
Application number: CA277,476A
Authority: CA
Inventors: Norio Komano; Kazuyuki Kobayashi
Original assignee: Hisaka Works Ltd
Current assignee: Hisaka Works Ltd
Priority date: 1976-10-14
Filing date: 1977-05-03
Publication date: 1980-09-23
Also published as: FR2367961B1; GB1562335A; FR2367961A1; DE2722867A1; SE7704464L; DE2722867C3; DE2722867B2; SE424906B

Abstract

ABSTRACT OF THE DISCLOSURE
A gasket for use in a plate type heat exchanger comprises an elastic material, such as rubber, covered with a U-shaped Teflon sheet. The elastic material and Teflon sheet are integrally joined together by an adhesive agent or by meshing with each other. Alternatively, the required region of the outer periphery of a gasket made of an elastic material may be covered with a Teflon sheet.

Description

"" 1086301 The present invention relates to a gasket for use in a plate type heat exchanger.
Conventionally, gaskets for use in a plate type heat exchanger have been uniformly formed of an elastomeric material which can be safely used on the severest conditions during heat exchange. However, such gaskets will have higher resistances to corrosion and elastic deformation than is necessary in a region where the conditions are rather favourable. As a result, if used for a long time, the gaskets deform and the plates warp.
Further, most of the gaskets used hitherto in such plate type heat exchangers have been made of an elastomeric material such as synthetic rubber from the standpoint of fluid tightness. There is no problem with such gaskets so long as non-corrosive liquid or gas is used, but when chemicals such as organic solvents are handled, since synthetic rubber is inferior in its resistance to chemicals the portion of the gasket which is contacted with an organic solvent, is corroded, losing fluid tightness. Therefore, plate type heat exchangers have been regarded as unsuitable for heat exchange of such fluids as organic solvents.
`In order to eliminate such disadvantages, use of a gasket made of Teflon (trade mark) which is superior in resistances to heat and chemicals would be contemplated, but Teflon has no elasticity and a high degree of hardness, so that it is unsuitable for use as a sealing material. Thus, in order to obtain sufficient fluid tightness, it would be necessary to clamp the plates with a considerably strong force. For this reason, it is unsuitable for use with thin plates.
It is an object of the present invention to eliminate the disadvantages of conventional gaskets used in plate type heat exchangers.
Another object of the invention is to provide a gasket having characteristics which meet the conditions for contact in ' 1~)B630~
various positions on the plates.
A further object of the invention is to provide a gasket for use in plate type heat exchangers which is supe-rior in elasticity and resistances to heat and chemicals.
Accordingly, the present invention provides a gas-ket comprising an elongated elastic core describing a closed loop of irregular configuration with a cross-section having top, bottom, inner and outer side surfaces,and a mating elon-gated Teflon* cover member of uniform U-shaped cross-section -also having an irregular configuration and encasing said core on said top, bottom and inner side surfaces, the cover member being of substantially uniform thickness and being provided with means positively securing the core member within the cover member.
The elastic core material may be natural or synthe-tic rubber and may be secured by adhesive bonding to the Teflon* cover or by meshing of the material and cover.
Said gasket has a suitable degree of elasticity and is capable of maintaining fluid-tightness between the plates with a relatively small force whilst its surface of contact with heat exchange liquid is superior in resistances to heat and chemicals.
Other numerous features which are characteristic of the present invention will be fully described with reference to the accompanying drawings illustrating embodiments of the invention and in which:
Figure 1 is a schematic front view of a plate and a gasket generally used in a plate type heat exchanger;
Figure 2 is a schematic front view of a plate pro-vided with a gasket according to the invention;

Figure 3 is an enlarged sectional view showing themounting of a gasket according to the invention;

* Trade Mark ,. ~ ~

1(~86301 Figure 4 is an enlarged sectional view of the prin- -cipal portion of another embodiment of the invention, similar to Figure 3;

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Figure 5 is a perspective view of a gasket according to a further embodiment of the invention;
Figure 6 is a perspective view, partially broken away, of the gasket of Figure 5 installed between plates in a heat exchanger; and Figures 7 through 9 are cross-sectional views of gaskets, showing the condition of engagement between an elastic material and a Teflon sheet.
In a known kind of plate type heat exchanger, as :~
10 shown in Figure 1, each heat exchange plate, is provided at the ~:
four corners with openings 1, 2, 3 and 4 serving as inlet and outlet ports for a heat exchanger fluid, for example, liquid or gas. Thus, the heat exchanger includes a plate A having a gasket 5a mounted thereon so as to surround the openings 1 and

2 disposed on a diagonal line to establish communication therebetween while shutting off the other openings 3 and 4, and .
a plate B having a gasket 5b mounted thereon so as to surround the openings 3 and 4 to establish communication therebetween while shutting off the other openings 1 and 2. A plurality of :20 such plates A and B are alternately put together with clearances defined therebetween providing fluid channels or heat exchange chambers ~llowing dissimilar heat exchange fluids to flow therethrough with one plate A or B between such fluids. For example, if high temperature fluid is supplied through the openings 1 while supplying cold water through the openings 3, ` the high temperature fluid flowing in through the openings 1 passes along the surfaces of the plates A during which time it exchanges heat with the fluid in the adjacent heat exchange chambers, namely the cold water, and flows out through the ; 30 openings 2. On the other hand, the cold water passes from the openings 3 along the surfaces of the plates B during which time it exchanges heat with said high temperature fluid flowing through the adjacent fluid channels with the plates A

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, . . , , . .. .; ~ ~,,,. . . . ., ~ ., 1~86301 therebetween and flows out through the openings 4. In addition, the entire surface of each of the plates A and B is provided with a number of ridges and recesses in order to improve the efficiency of heat exchange, and the gaskets 5a and Sb are mounted by making use of the recesses.
Now, since the high temperature fluid passing from the openings 1 onto the plates A is heat-exchanged on the plates A, the condition of the fluid does not necessarily remain constant but varies with different locations on each plate A and hence the conditions for its contact with each gasket 5a vary. More particularly, the temperature of the fluid differs between a region near the openings 1 and a region near the openings 2 and hence the condition of deformation of the gaskets 5a also differs. If the fluid is a non-corrosive one, such as water, there is no trouble, but if it is an organic solvent, there is the problem of the contact surfaces of the gaskets being corroded. Moreover, since organic solvents vary in their corrosive nature according to temperature, there will be the phenomenon of some regions of the gaskets 5a being attacked with other regions not being attacked.
Referring to Figure 2 showing a first embodiment of the invention, a gasket shown at 15 is mounted on a plate lOA.
- The gasket 15 is formed of an elastic material 16, such as rubber, and a thin Teflo ~ sheet 17 highly resistant to heat and corrosion. More particularly, the elastic material 16, applied to a region where the conditions for contact during heat exchange are relatively favorable, is formed uniformly to the size of the gasket 15, while the portion of the elastic material exposed to a region where the conditions for contact are severe has the U-shaped Teflon sheet 17 adhesively fixed thereto in such a manner that its lateral surface 17a defines a surface of contact with a heat exchange fluid. The Teflon sheet 17 is pre-bent to the shape of the portion of the elastic material 16 _ 4 -~(~86301 on which it is to be mounted so as to facilitate the mounting ~' of the Teflon~sheet on the elastic material.
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The surface of the plate lOA, on which the Teflon~
sheet 17 is to be seated, is formed with a step lOa corresponding to the thickness of the Teflon sheet 17, as shown in Figure 3, so as to avoid positional misalignment when the gasket 15 is mounted. Further, as shown in Figure 4, the upper and lower surfaces of the elastic material 16 may be formed with steps 16a and 16b for receiving the Teflo~ sheet 17 to prevent the latter from projecting out of the elastic material 16.
Thus, when a chemical such as a solvent is handled, the use of the gasket 15 constructed in the manner described ~ 5 -1~863()1 above allows heat exchange to be performed in the same manner as in the past without being attacked by the heat exchange fluid and variations in the conditions for contact at various positions on the plate can be effectively accommodated by the character-istics of the elastic material 16 and Teflon~sheet 17, which differ in their resistances to heat and corrosion. Moreover, the same state of contact exists over the entire gasket 15 irrespective of temperature differences and corrosiveness, even if used for a long time, and hence the plates will not warp.
Referring to Figure 5 showing a second embodiment of the invention, a gasket is shown at 25. The gasket 25 comprises an elastic material 26 such as synthetic rubber of rectangular cross-section covered with a thin Teflon sheet 27 formed into a U-shaped cross-section.
Referring to Figure 6, the width of the Teflon sheet 27 is substantially the same as the width of a gasket groove 28a or 28b in a plate 20A or 20B and the height of the lateral surface 27a is greater than the depth of the groove 28a or 28b.
Therefore, when the gasket 25 is mounted, for example, in the groove 28b, the upper portion of the lateral surface 27a faces the fluid channel and the upper portion of the gasket 25 projects above the groove 28~.
In mounting the elastic material 26 to the Teflon sheet 27, the Teflo~rsheet 26, pre-bent into a u-shaped cross-section, is circularly or flaringly formed as by a roller while applying heat in such a manner that its lateral surface 27a becomes an inner peripheral surface, and the elastic material 26 is then mounted to the Teflon sheet. The surface of the Teflon sheet 27 is smooth and very slippy and the gasket is long and narrow, ernclrk - 6 -~63~1 so that, if the plates 20A and 20B are clamped, there would be a danger that the elastic material 26 would be squeezed out ~-~,of the open side of the Teflon sheet 27 as it is deformed. To prevent this, the inner surface of the Teflon sheet 27 is surface-treated and an adhesive agent is applied thereto to fix the two members together. Further, if the gasket 25 is adhesively secured to the gasket groove 28b of the plate 20B, plate assembling operation is facilitated.
Further, fixing of the elastic material 26 to the Teflon~
sheet 27, or their integration, may be effected by resorting to engagement or meshing relation therebetween as shown in Figures 7 through 9 rather than resorting to the adhesive agent. Thus, in an embodiment shown in Figure 7, a projection 27b is formed on the inner surface of the Teflo ~sheet 27 and fixing is effected by said projection cutting into the elastic material.
In Figure 8 the inner surface of the Teflo~ sheet 27 is roughened or corrugated. In Fy ure 9, cores 29 in the form of piano wires or the like are embedded in the elastic material 26 to increase the resistance of the elastic maberial to deformation. These forms may be suitably selected according to the clamping force on the plates 20A and 20B.
On the plate 20B, having the gasket 25 adhesively applied to the gasket groove 28b, is placed the back surface of the other plate 20A, with the bottom of the groove 28a contacted with the gasket 25, and in this condition the assembly is clamped whereby a fluid channel or heat exchange chamber 20C is defined between these pla~es. ThUs, intimate contact of the gasket 25 with the surfaces of the respective plates is established with a relatively small clamping force and the heat exchange 108~301 fluid contacts only the Teflon sheet 27 of the gasket 25.
~` Thus, handling of organic solvents for heat exchange becomes possible. Further, the function described above prevents the elastic material 26 from being squeezed out of the Teflo~ sheet 27 when the plates 20A and 20B are clamped, and hence reliable sealing is assured.
While what have been described heEèin are at present considered to be preferred embodiments of the several features of the invention, it will be obvious to those skilled in the art that modifications and changes may be made without departing from the essence of the invention.
It is therefore to be understood that the exemplary embodiments thereof are illustrative and not restrictive of the invention, the scope of which is defined in the appended claims, and that all modifications that come within the meaning and range of equivalency of the claims are intended to be included therein.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A gasket comprising an elongated elastic core describing a closed loop of irregular configuration with a cross-section having top, bottom, inner and outer side surfaces, and a mating elongated Teflon* cover member of uniform U-shaped cross-section also having an irregular configuration and encasing said core on said top, bottom and inner side surfaces, the cover member being of substantially uniform thickness and being provided with means positively securing the core member within the cover member.

2. A gasket having an irregular configuration for use in a plate type heat exchanger having a channel therein to accommodate said gasket, comprising an inner elongated elastic core member describing a closed loop of irregular configuration, and having top, bottom, inner and outer side surfaces defining a core member having a quadrilateral con-figuration uniform in cross-section throughout its length, a mating elongated Teflon* cover member having top and bottom portions spaced from one another and joined to one another by a side portion thereby defining a cover member U-shaped in cross-section, said cover member being of substantially uni-form thickness throughout its length and having said top, bottom and side portions of said cover member encasing only a portion of the elongate extent of the core member on said top, bottom and inner side surfaces, with the remaining por-tion of the elongate extent of the core member having no cover, and an adhesive film interposed between said inner core member and said outer cover member thereby securing said inner core member and said outer cover member to one another in tight engagement therebetween.

* Trade Mark

3. A gasket in accordance with Claim 2, wherein the top and bottom surfaces of the core member receiving the cover member are each in stepped relation to the un-covered top and bottom surfaces of the core member, so that the assembled gasket is of uniform thickness throughout its length.

4. A plate type heat exchanger having a plurality of plate elements spaced from one another in side by side relationship, each of said plate elements having an endless gasket groove in the surface thereof, a gasket describing a closed loop positioned in the gasket groove of each plate, said gasket comprising an inner elongated elastic core member having top, bottom, inner and outer side surfaces thereby defining a core member having a quadrilateral configuration uniform in cross-section throughout its length, a mating outer Teflon* cover member having top and bottom portions spaced from one another and joined to one another by a side portion thereby defining an elongated cover member U-shaped in cross-section, said cover member being of substantially uniform thickness throughout its length and the top and bottom portions and the side portion thereof being in envelo-ping engagement with the corresponding top, bottom and inner side surfaces of the core member, and means securing the inner core member and the enveloping outer cover member to one another in tight engagement therebetween, the uncovered outer side surface of the core member facing outwardly of the heat exchanger.

5. A gasket in accordance with Claim 4, wherein the means securing the inner core member and the outer cover member to one another is an adhesive film therebetween.

* Trade Mark

6. A gasket in accordance with Claim 4, wherein the means securing the inner core member and the outer cover member to one another is interior top and bottom surfaces of the cover member which are roughened or corrugated.

7. A gasket in accordance with Claim 4, wherein a piano wire is embedded lengthwise in the core member.