Seals and Sealing

Most critical subsea and downhole equipment (e.g., packers, valves, actuators, rams) relies on non-metallic seals in order to function. Elastomers have been largely displaced as the primary seal in valve stems for HP service by stacks in which the primary and secondary seals are spring-energised PTFE. Elastomers, usually in the form of O-rings, are still important sealing materials: they are more forgiving of housing surface defects, for example. High performance elastomers include HNBR, FKM, TFE/P and FFKM. The majority of elastomers function over the long term under stable operational conditions. However, when a large change in condition occurs, sealing can be compromised. Examples of seal-threatening changes include: rapid gas decompression events, contact with chemically aggressive species, large temperature reduction, and time at HPHT conditions.