EXPLOSIVE DECOMPRESSION AND OTHER O-RING RELATED ISSUES FOR TURBOMACHINERY SERVICE-SOME USER GUIDANCE

摘要

Flexible sealing elements, typically elastomeric O-rings are commonly used to contain fluids within pressurized cavities of turbomachinery at the interfaces between adjoining components. All too often the only selection criteria applied for these sealing element is chemical resistance and a check that the service conditions are within the published temperature limits for the material being considered. This seemingly simplistic selection process can be complicated when the fluid in question, comprised of numerous constituents that dictate several different elastomeric materials, would normally be the optimal selection. Furthermore in the case of duties where the fluid (typically gas) pressure is elevated, some additional considerations also become more prominent due to explosive decompression (ED) damage that can occur during rapid depressurization events in the pressurized system. Despite the effects of ED being well documented, there is still a relative lack of understanding regarding what makes a sealing device "ED resistant" and why. This tutorial goes through the composition of flexible sealing element materials and how they compare with a more widely understood engineering material; steel. It also focuses on sizing issues and international standards and how they are applied in given applications. Thermal considerations will also be addressed and an appreciation of the methods used to test such materials will be covered. In addition to ED topics being fully addressed there will also be other issues covered such as storage and longevity, modulus, strength, hardness, elongation, compression set, and stress relaxation. Lastly, although this tutorial focuses mainly on O-rings it can equally be applied to any elastomeric sealing material used in the turbomachinery industry.