Valve Magazine - Spring 2012

Figure 3. Valves used in upstream applications
Ball
Gate
Globe
TOV
ACTUATION

Torque should also be continually
measured and monitored during testing
of both gear-operated and actuated
valves. It is important to note that at no
time during testing should an operator
be allowed to increase torque, even if
this will result in better sealing. This is a
fundamental requirement to ensure reli-
able actuator selection and to maintain
valve tightness performance over the
time in service.

ZERO LEAKAGE Zero leakage is defined as the ability to pass a test with no visible leakage during test duration as defined by API 598 and API 6D. All TOVs, gear-operated or actuated, must be zero leakage with

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TESTING

It is important to emphasize how testing is conducted in a controlled manner of a TOV to be sure that zero leakage is achieved.

The standard test procedure for all TOVs is a zero leakage bench test that allows “open face” testing (in other words, no blind flanges, pipes or bubblers are used) and always applies a controlled torque. This allows an inspector to observe the sealing surfaces of the valve when under pressure and eliminates any form of manipulation of the test to hide possible leakage, even in the relatively short test time specified by international standards.