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The many, varied demands placed on gaskets

A common perception is that the suitability of a gasket for any given application depends upon
the maximum temperature and pressure conditions. This is not the case.

Maximum temperature and pressure values alone can not define a material’s suitability for
an application. These limits are dependent upon a multiplicity of factors as shown in the diagram
opposite. It is always advisable to consider these factors when selecting a material for a given application.

Selecting gaskets with pT diagrams
The Klinger pT diagram provides guidelines for determining the
suitability of a particular gasket material for a specific application
based on the operating temperature and pressure only.
Additional stresses such as fluctuating load may significantly
affect the suitability of a gasket in the application and must be
considered separately. Always refer to the chemical resistance
of the gasket to the fluid.
Areas of Application

(1) In area one, the gasket material is normally suitable
subject to chemical compatibility.
(1) In area two, the gasket materials may be suitable but a
technical evaluation is recommended.
(3) In area three, do not install the gasket without a technical

*Gaskets according to DIN 2690 are only standardised
up to PN 40 and gasket thickness 2 mm.

Klinger Hot and Cold Compression Test Method
The Klinger Hot Compression Test was developed by Klinger as a method to test the load bearing capabilities of gasket materials under hot and cold conditions.

The diagram shows additional thickness decrease at temperature
In contrast to the BS 7531
and DIN 52913 tests, the Klinger
Compression test maintains a
constant gasket stress
throughout the entire test.
This subjects the gasket to more
severe conditions.
The thickness decrease is
measured at an ambient temperature
of 23°C after applying the
gasket load.
This simulates assembly.
Temperatures up to 300°C
are then applied and the
additional thickness decrease is
measured.This simulates the
first start up phase.
Temperatures up to 300°C are then applied and the additional thickness decrease is measured.This simulates the
first start up phase.

The maximum surface pressure under operating conditions is the maximum allowable surface pressure on the effective gasket area under service conditions that can be applied to the gasket before unacceptable laxation of the flanged joint occurs and/or the gaskets are destroyed.

The diagram above shows this values for different gasket thicknesses.
Min. surface pressure σVU for tightness classes
L= 1.0, L = 0.1 and L = 0.01 in accordance to DIN 28090

The minimum surface pressure is the
minimum surface pressure that should
be applied to the gasket to achieve
the necessary tightness requirements.

The value must be sufficient to
compress the material into the flange
imperfections, reduce the materials
porosity and also counteract the
release of load due to the internal

The diagrams below show the
minimum gasket stress required to
achieve the relevant tightness classes
as a function of thickness.

Tightness class L= 0.1
allows a maximum leakage of
0.1 mg nitrogen per second per meter
of gasket length (mg/s x m)

Minimum surface pressure σBU for tightness class L = 0.1
The three dimensional diagram below
describes the behaviour of 2 mm
gasket material with respect to the
minimum surface pressure to achieve
a tightness class of L = 0.1 under a
wide range of temperatures and
internal pressures. It clearly shows
that the minimum surface pressure
decreases at elevated temperatures –
the gasket will seal at lower loads
under these conditions.
Modulus of elasticity ED in accordance to DIN 28090
This diagram outlines the modulus of
elasticity compared to the surface
load. The curves describe the
behaviour at ambient temperature
and at 200°C.