Standard Leakage Rate


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Leakage Class Designation Maximum Allowable Leakage Test Medium Test Procedures Testing Procedures Required for Established Rating
I       No test required provided user and supplier so agree
II 0.5% of rated valve capacity Air or water at 50° to 125° F 45 - 60 psig or maximum operating differential, whichever is lower Pressure applied to valve inlet, with outlet open to atmosphere or connected to a low head loss measuring device, full normal closing thrust provided by actuator
III 0.1% of rated valve capacity As above As above As above
IV 0.01% of rated valve capacity As above As above As above
V 0.0005 ml per minute per inch of port diameter per psi differential Water at 50° to 125° F (10° to 52°C) Maximum service pressure drop across valve plug, not to exceed ANSI body rating (100 psig pressure drop min.) Pressure applied to valve inlet after filling entire body cavity and connected piping with water and stroking valve plug closed. Use net specified max. actuator thrust, but no more, even if available during test. Allow time for leakage flow to stabilize.
VI Not to exceed amounts shown in table 2* based on port diameter *Consult Factory Air or nitrogen at 50° to 125° F (10° to 52° C) 50 psig or maximum rated differential pressure across valve plug, whichever is lower Actuator should be adjusted to operating conditions specified with full normal closing thrust applied to valve plug seat. Allow time for leakage flow to stabilize and use suitable leakage measuring device.

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