Determination of the Initial Gaps between Flat Flanges without Gaskets

Abstract

This paper describes a method of finding the size and shape of the gaps which exist between the faces of an assembled but unloaded fiat-faced, metal-to-metal flange joint. The low-pressure leakage of 26 such assemblies has been measured experimentally, and pressure tappings have been used to record the pressure distribution under the contact faces of some of the flanges. Formulae are derived for the conversion from experimental data to gap size and shape. The method gives a very sensitive measure of gap height because of the cubic nature of the conversion formulae. Gap heights in the range 4–30 μm have been found. It is shown by finite element calculations that deflections due to boll loading of a perfectly flat flange are much smaller than the observed initial gaps.