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Life estimation for complex systems ultimately involves a suite of models for the various potential product failure modes. The advances in gasket test and analysis techniques presented in this paper lay the foundation for development of this future predictive capability. Static sealing performance factors of creep-relaxation, fatigue resistance, and leak rate are three principal determinants of application sealing success. This paper explores progress in each of these areas and presents concepts needed to integrate them into a coherent, probabilistic methodology.

Modern, metal-based, static seal technologies are more sensitive to component flange surface finish effects than their softer, composite cousins. Non-averaging or skidless profilometer instruments are capable of accurately resolving the short-wavelength roughness and long-wavelength waviness components of a surface profile. Simple roughness measurements of a surface often ignore the important waviness features that can result in sealing difficulties with these seal technologies. This paper presents techniques for proper surface profile filtering and investigates the impact of waviness conditions on basic, static sealing performance.

The response of a gasketed, bolted joint to an external load is understood to be effected by all components involved in the joint. The analysis involves the equilibrium of the gasket compressive force with the bolt tension force and the forces external to the bolted joint. Geometric compatibility is maintained when the change in the stretch of the bolt caused by an external force is equal to the change in compressed thickness of the gasket. When the flanges are treated as nondeformable, the classical joint diagram analysis indicates that externally applied loads, which unload the gasket, increase bolt tension. In this paper, the effect of flexible flanges is included in the analysis of simple gasketed bolted flanges. The results show that bolt tension response can deviate significantly from the rigid flange behavior. In certain situations where flanges have a relatively high level of flexibility, external joint forces that unload the gasket also unload the bolt.

A test system is presented that performs gas sealability tests on gasket materials and components. The system is computer controlled and capable of providing elevated compressive loads and gas pressures. It incorporates a personal computer controller interface, a hydraulic load frame, and integrated gas pressure control. Gas leakage is measured using a mass flowmeter. It performs several multiple-condition tests, the most important being a load sequence sealability test at constant gas pressure and a pressure and load sequence sealability test. The test system provides for automatic test control and data acquisition, so that the test sequences can run unattended. An overview of sealability test methods is included to provide perspective regarding this development.

A bolted joint mathematical model is presented which includes flange bending effects. The approach simulates the behavior of a system of elastic flanges, a one component non-linear gasket, and linear elastic bolts subjected to assembly and pressurization loadings. Flange distortion is introduced to the joint diagram to predict the overall, midspan, and under the bolt gasket loads.