When performing a hydrostatic test on a boiler, what must be done to each safety valve?

During a hydrostatic test on a boiler, it is essential to blank or gag each safety valve to ensure that they do not release pressure during the testing process. A hydrostatic test involves filling the boiler with water and pressurizing it beyond its normal operating pressure to check for leaks and structural integrity. If safety valves were left functional during this test, they could open prematurely, disrupting the test and potentially causing inaccurate results or leading to safety hazards.

By blanking or gagging the safety valves, you effectively prevent them from responding to the test pressures. This allows the boiler to be tested under controlled conditions without the risk of the safety valves interfering. Once the hydrostatic test is complete and the boiler is deemed safe for operation, the safety valves can then be returned to their normal, functional state.