22 Jul 10 10:04
I did a reveiw of the literature on test duration for a safety manual chapter I participated in writing a few years ago (see Safety Manual
) and what it says still holds
Determining the length of a test, when a test should start, and if a test is successful has been the source of much discussion. Customs and regulations often specify test durations (e.g., static tests in several European countries are required to run for 24 hours after stabilizing). Sometimes local management sets the test duration (e.g., in some chemical plants, tests are required to be completed after 15 minutes). Absent regulation or local management requirements, ASME B31.8 specifies that tests should be held for 2 hours, but is silent on when the test actually starts. This is a critical omission because most procedures prohibit adding test media during the actual test. The test procedure should specify when the clock starts on the test. For hydrostatic tests, the start time should include an adequate delay for temperature to equilibrate and for dissolved gases to evolve from the water. For a gas test, a short time delay for temperature equilibration is necessary
David Simpson, PE
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