Pressure Relief Valve Testing and Repair PDF

Objective 3 Describe the testing and repair of pressure relief valves. TESTING PRESSURE RELIEF VALVES Pressure relief valves must be kept in good working condition at all times. Test these valves regularly to make sure they are functioning properly. Common tests include: • Try lever test • Pop test...

Objective 3 Describe the testing and repair of pressure relief valves. TESTING PRESSURE RELIEF VALVES Pressure relief valves must be kept in good working condition at all times. Test these valves regularly to make sure they are functioning properly. Common tests include: • Try lever test • Pop test Side Track Consult Part B, Unit 4, Chapter 4 Operational Checks, as well as ASME BPVC Sections I, IV, VI, and VII, for detailed descriptions of pressure relief valve test procedures. Try Lever Test A try lever test determines if a pressure relief valve is operating freely. However, it does not determine if the valve will open at its set pressure. Try lever tests are performed: • Monthly on steam heating boilers • Every three months for hot water heating boilers • Every six months on power boilers that operate below 2760 kPa These tests are also performed prior to pop tests and accumulation tests. Boilers must be under pressure before conducting try lever tests. Steam heating boiler pressure must be 35 kPa or higher. A power boiler’s pressure must be at least 75% of the setting of the safety valve. To perform the test: 1. Pull the try lever on the safety valve to the wide-open position. 2. Allow steam to discharge for 5 to 10 seconds. 3. Release the lever. 4. Allow the spring to snap the valve disc to the closed position. If the valve simmers after the test (i.e. steam continues to discharge from the valve), operate the try lever two or three times to allow the disc to seat properly. If the valve continues to simmer, it must be repaired or replaced. Pop Test The full operation of the safety valve, including the exact pressures at which it opens and closes, can be checked using the pop test. To perform this procedure: 1. Increase the boiler steam pressure to the safety valve set point. 2. Accurately record the opening and reseating pressures. Once the pressures are established, the blowdown can be determined. 3. Compare the opening pressure and blowdown to the performance tolerances outlined in the relevant section of the ASME BPVC (I or IV). Use this information to determine whether the valve is operating properly, or if it requires repair or replacement. Pop tests should be performed annually, before taking a boiler off-line for maintenance. This will identify any defective valves so that they can be replaced or repaired prior to the boiler re-entering service. REPAIRING PRESSURE RELIEF VALVES All ASME BPVC sections require that the repair or adjustment of pressure relief valves be done by the valve manufacturer or its authorized repair representative. Consult with the relevant ASME BPVC sections, and the local Boiler Inspector, to determine who is qualified to adjust or repair PRVs in a particular jurisdiction.