Estimating leak rates of circular gaskets under nonuniform contact pressures using EN 13555 test data

Abstract

Design and evaluation of bolted flange connections for pressure vessels and piping increasingly requires tightness estimates, which can be quantified by leak rate. Procedures according to standard EN 1591–1 in conjunction with gasket test data according to EN 13555 allow bolted flange connection leak rate estimation based on gasket contact pressure history. During the test, leak rate is measured at uniform gasket contact pressure distributions. However, at operating conditions, the contact pressure is generally not uniform, which leads to nonuniform fluid leakage through the seal. For estimating leak rate in such cases, local fluid conductance in radial as well as circumferential direction would have to be known, however the conductance can be deduced only for radial direction from the tests. This paper takes advantage of an assumption, that circumferential fluid conductance must be positive, i.e., between zero and infinity. Expected leak rate interval based on this assumption is narrower than interval between minimum and maximum leak rate estimated from extreme gasket contact pressures, leading to more precise estimates.