A term used to describe certain standardized testing procedures for control valves with a flow coefficient greater then 0. 1 (C_v). These procedures are outlined in ANSI Standard d B16. 104-1976, which gives specific tests and tolerances for six seat leakage classifications. It should be remembered that these tests are used to establish uniform acceptance standards for manufacturing quality and are not meant to be used to estimate leakage under actual working conditions. Nor should anyone expect these leakage rates to be maintained after a valve is placed in service. There is no standard test for self-contained regulators at this time. Note! You will see many instances where regulators are specified using the above criteria.