A leakage class has meaning only within its referenced standard and test conditions. Terms such as tight shut-off and bubble-tight should be translated into a specific, agreed acceptance requirement.
Define the test conditions
The result depends on test medium, pressure, temperature, flow direction and how the actuator seats the valve. A class measured with air at prescribed conditions is not automatically a field guarantee for a hot abrasive liquid at another differential pressure. The actual leakage limit may depend on valve size or other standard provisions.
Do not combine different standards casually
Control-valve leakage classifications and isolation-valve test specifications may use different methods and acceptance criteria. A label from one system should not be treated as a direct equivalent to a label from another without checking the applicable text. Specify the current edition required by the project and ask the supplier to confirm compliance.
Keep control and safety functions distinct
A tight control-valve seat does not replace a plant isolation procedure. For hazardous maintenance, the required isolation arrangement comes from the facility’s design and operating rules. During procurement, identify the required shut-off role separately from modulation and require the proper documentation for that role.
Practical checklist
- Exact standard, edition and class.
- Test medium, pressure, temperature and direction.
- Actuator configuration during the test.
- Acceptance record linked to the supplied valve.
Discuss your application
Send the process conditions and required valve function for a configuration review. Request a technical quotation ↗