Page 32 - Valve Selection Handbook
P. 32
Fundamentals 19
Gasket Blowout
Unconfined gaskets in flanged joints may blow out prior to leakage
warning when inadequately designed.
This mode of gasket failure will not occur if the friction force at the
gasket faces exceeds the fluid force acting on the gasket in the radial
direction, as expressed by the equation:
where
(X = friction factor
F = gasket working load
P = fluid gauge pressure
t = gasket thickness
= mean gasket diameter
d m
The joint begins to leak if:
in which
m = gasket factor
w = gasket width
The gasket factor is a measure of the sealing ability of the gasket, and
defines the ratio of residual gasket stress to the fluid pressure at which
leakage begins to develop. Its value is found experimentally.
It follows thus from Equations 2-3 and 2-4 that the gasket is safe
against blowout without prior leakage warning if:
Krageloh 8 regarded a gasket factor of 1.0 and a friction factor of 0.1
safe for most practical applications. Based on these factors, the width of
