Leak Tests at Real Bolted Flange Joints - Verification of Gasket Characteristicsdetermined with Standardized Test Procedures

摘要

A prerequisite for the strength and tightness proof of bolted flange joints is the knowledge of gasket behaviourrepresented by several gasket factors. For floating type flanges joints, different calculation methods are used (e.g. ASMEcode in USA, the new European code EN 1591, or the KTA code 3211.2). Specific sets of gasket factors are defined whichcan be related to each other. For the choice of a gasket for given boundary conditions (construction, loading, temperature,medium,..) as well as for the calculation of bolted flanged joints (strength and tightness proof) gasket characteristics arerequired which reflect the deformation behaviour and sealing capability of the gasket. These gasket characteristics have tobe determined with standardized test procedures in order to obtain comparable, reproducible and transferable results. Fortechnical and economical reasons, the testing conditions of the standardized test procedures have to be idealised andsimplified. But it is obvious that these testing conditions are not fully capable to consider the real conditions at bolted flangejoints e.g. bending of flange blades, finite bolt distance, scatter of bolt load, or surface quality of flange face which mightinfluence the actual leak rate significantly. Especially for existing flange joints at running power plants, there an exchangeof flanges should be avoided, the fully knowledge about the actual leak behaviour during service is required to maximizetightness and to minimize material stress.