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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
*Gaskets according to DIN 2690 are only standardised
up to PN 40 and gasket thickness 2 mm.
(1) In area one, the gasket material is normally suitable subject to chemical compatibility
(2) 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 evaluation.
Klinger Hot and Cold Compression Test Method
The diagram shows
additional thickness decrease at temperature
The Klinger Hot Compression
Test was developed by the
Klinger Group as a method to
test the load bearing capabilities
of gasket materials under hot
and cold conditions.
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.
Maximum permissible surface pressure σBO under operating conditions acc. DIN 28090 – 1
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 relaxation
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.