How New Materials Ensure Reliable Sealing of Heat Exchangers

Related Vendors

DÜPERTHAL Sicherheitstechnik GmbH & Co. KG

Glatt Ingenieurtechnik GmbH

Italvacuum, Srl

W. L. Gore & Associates GmbH Werk 1

Monoaxial expansion is the older technique used to produce ePTFE gasket tapes. With this method, the PTFE is stretched to the tape only longitudinally. The texture that this creates is responsible for the weaker transverse strength. This results in greater broadening during initial compression, an aspect that must be taken into consideration in the design. Broadening of 20 % and more is quite common. The advantage that monoaxially expanded gasket tapes offer is that they can be compressed to be very thin during installation.

This means they are able to adjust to micro unevenness very easily. Macro unevenness on the other hand is quite difficult to compensate for with this type of gasket tapes. Furthermore, unlike with multiaxial expansion, the ends can be overlapped. Nevertheless, monoaxially expanded gasket tapes are used only very rarely in heat exchanger applications because the lack of transverse strength results in a higher creep tendency. Although the small installation thickness compensates for this to some degree, the performance gap to multiaxially expanded PTFE gasket tapes increases as temperatures rise.

Resistance to Creeping

The multiaxial expansion of the material takes place in the direction of two vectors that stand at right angles to each other. This results in a multiaxial structure, in other words an orientation of the emerging fibrils in all directions. The transverse texture can be produced by varying the intensity of the expansion.

Among other things, it helps to keep the nodes small because this non-oriented material contributes to creeping. Multiaxial expansion is of particular advantage in that it offers high transverse strength and allows for gasket tapes that are particularly resistant to creep.

Heat Exchangers

How Plate–and–Shell Heat Exchangers Work

Multiaxially Expanded PTFE Gasket Tapes Seal Reliably

The process of expansion compensates for the disadvantage of the PTFE material, its high creep tendency, and results in a chemically stable, creep-resistant sealing material. If expansion takes place multiaxially, the creep tendency of the material will be reduced to such an extent that it can then be used as a sealing material under extreme conditions of both chemically aggressive media and frequent major temperature load changes.

* *The author works for W. L. Gore & Associates Sealant Technologies, Putzbrunn/Germany.

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