PURPOSE
1.1 This standard establishes a series of seat
leakage classes for control valves and defines the test
procedures.
2. SCOPE & LIMITATIONS
2.1 Selection of a leakage class is not restricted as
to valve design, but acceptable values for various
commercially available designs are suggested for
each class under Section 4.
2.2 The standard cannot be used as a basis for
predicting leakage at conditions other than those
specified.
2.3 This standard is similar to IEC 60534-4, except
that no provision is made for Class IV-S1 and the
standard is applicable for valves with a Cv value less
than 0.1. The air leakage test and allowable leak
rates for Class V are equivalent to the water test and
allowable water leakage rates for a water test
performed at a nominal temperature of 60ºF