Background-Information for gasket data and calculation codes

Flanged joints are normally composed of flanges, bolts and the gasket. As for other such assemblies, calculations can be carried out that try to simulate the system mathematically. The calculation can tend to pure mechanical aspects (strength) and/or tightness (leak rate). Naturally, there are several alternative forms of calculations.

The calculation methods are detailed in standards. Further standards specify the characteristic gasket parameter values or the method of their determination for a particular calculation method. Because of this characteristic gasket parameter values from different standards are not necessarily transferable. Therefore the relevance, for a particular calculation method, of an available gasket parameter value has to be assured before a calculation is undertaken.

The ideal case, with both a calculation method and the relevant gasket data available, has not always been the case.

Up to now, gasket factors (in Germany) were generated by test methods according to DIN 28090-1. Data from that standard was intended to be used for the pre-calculation code DIN 2505 which has been updated and revised several times. In the future EN 1591-1:2001 will be used more often, as all aspects of a flanged joint are taken into account. The gasket data required by EN 1591-1:2001 must be generated according to EN 13555:2005 and with the publication of EN 13555, DIN 28090-1 has been withdrawn as an official standard.

The following table illustrates the gasket data of EN 13555:

Gasket dataDescription
QA [MPa]Gasket stress at assembly.
Qmin(L) [MPa] Minimum stress to seal for leakage rate L during installation
QSmin(L) [MPa]Minimum stress to seal for leakage rate L in service
QSmax(T) [MPa]Maximum allowed gasket stress at temperature T (to be verified with PQR-test).
PQR [-]Creep-Relaxation Factor
EG [MPa] Modulus of Elasticity of the gasket
aG[K-1] Thermal expansion factor of the gasket