All butterfly valves, completely assembled, should be checked by the supplier in accordance with the accepted standard such as BS-5155 (stress testing) prior to dispatch.
Before valves are painted or otherwise externally covered with materials that can seal against leakage, testing should be carried out. Internal linings and internal anti-corrosion sealing treatments should be allowed for testing reasons.
No pressure testing valve should be subject to shock charging. Before pressure testing, valves and links should be cleaned of air.
For all pressure test, the test fluid should be either water with the addition of an appropriate inhibitor or another liquid whose ambient temperature viscosity is equivalent to or less than that of water.
In contact with austenitic stainless steel parts, attention is attracted to the need to regulate the chloride content of test water.
The following relationships should determine the test pressures:
1. Shell test: 1.53 maximum permissible, working pressure at 20°C.
2. Disk strength test (applicable to valves 14 in. and larger): 1.53 maximum permissible working pressure at 20°C.
3. Seat test: 1.13 maximum permissible working pressure at 20°C.
Testing processes for butterfly valve shell, disk and seat should be consistent with the accepted standard such as BS-5155.
As per BS-5155 Table 10, test durations for butterfly valves should be performed.
For each valve type, the highest permissible leakage should be provided in Table 11 of BS-5155 after the experiment performed by Table 10 above.