Much important electrical equipment is oil filled. The oil serves as both coolant and the primary electrical insulating medium. This oil must be contained, and kept very dry. Soft gaskets are installed around all the access covers and various connections. Not only do the owners of this equipment expect it to be free of leaks for 30 to 60 years, re-gasketing usually takes several days, often at a cost of tens of thousands of dollars, primarily in lost power delivery. Soft gasket materials are known to develop several undesirable characteristics in extended service. This test is intended to accelerate, in a controlled, repeatable way, the development of these undesirable characteristics. It involves compressing part of a sample coupon to its service thickness and immersing it in its intended fluid at a temperature somewhat higher than in normal service.
