The ISO 5208 rate A specify a leakage by internal tightness seat test (or often also called closure test) of valves. Usually one side (valve inlet) shall be subjected to the test pressure and amount of leak shall be measured on the opposite side of the valve to atmosphere. ISO 5208 specifies valve closure tests of an industrial metallic valve to verify the degree of valve closure tightness.
Industrial metallic valve types:
– Gate valves
– Globe valves
– Plug valve
– Check valve
– Floating ball valve
– Diaphragm Valve
– Butterfly valve
– Trunnion mounted valve
The test fluid shall be a liquid and/or gas.
ISO 5208 rate A
The test fluids are liquids or gases depending the types of valves (see above).
The necessary leakage rate must be determined by the operator or manufacturer as part of a risk analysis or there are legal requirements for the system operator. Leakage rates can be defined between the ordering party and the valve manufacturer, for which they can refer to test standards or the product standard itself contains tightness requirements
The leakage ISO 5208 rate A is one of 10 defined leakage rates. Generally the leakage rate is to specify by customer and are specified in the following valve product standards such as ASME B16.34, API SPEC 6D, ISO 13942.
The leakage ISO 5208 rate A defined the strongest rate with 0 (zero) leakage. It means that “No visually detectable leakage for the duration of the test” by a specified test condition.
ISO 5208 contain 2 tables, each for liquid and gas test fluids, with a leakage rate to be calculated depending on the nominal size (DN).
Further test conditions are specified in ISO 5208:
- Test fluid
- Timing of test
- Test pressure
- Duration of test
- Temperature of test fluid
Conclusion
ISO 5208 rate A is the strictest requirement class in this standard for the verification of internal tightness. The detection method is practicable, usually sufficient and can be used for many applications.
