Leak Tightness in Safety Valves

Main objectives:
1. Improve our overall understanding of the design of static face seals, the associated loading and degree of leak tightness.
2. Review of current sealing practice to identify potential analysis methods to assess leak tightness and valve sealing performance.
3. Application of FEA-based methods to investigate global deformation of seat and sealing elements and the influence on leak tightness in metal-to-metal contact.
4. Microscopic study of the surface roughness and asperities configuration using optical scanning with surface profilometer.
5. Develop a simple test facility to investigate leak tightness of PRV and validate the assumptions based on FEA.

1. Sealing and leakage prediction techniques:
a) Development of analytical model that includes effect of asperity deformation and gas rarefaction on leakage rates;
b) This model also incorporates the effect of seat length on the resultant leakage rate;
c) Quantification of the effect of surface roughness on fluid leakage.
2. Analysis of macro deformation of the valve seat/disc under various pressures using quasistatic structural FEA with fluid pressure penetration technique:
a) Macro deformation is important and affects sealing area;
b) Cyclic material response affects the structural behaviour significantly;
c) Type of fluid influences sealing surface through pressure distribution.