What are the precautions in valve operation and valve management?

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Precautions when operating valves: 1. For all manual drain and vent valves in the thermal system, they should be tightened once again half an hour after operation to eliminate any gaps caused by thermal expansion and contraction. 2. For thermal pipelines equipped with primary and secondary valves, the sequence for operating these valves is as follows: when opening them, the primary valve should be opened first, followed by the secondary valve ； When shutting down, close the secondary door first, then the primary door. 3. For operating the gate valve, it can only be fully closed or fully opened; a partially open position is not allowed, in order to reduce wear on the valve. 3 Precautions in valve management
1. Before starting the unit, conduct tests on all electric and pneumatic valves. During the tests, a dedicated person should be present to monitor the operation of the valves and dampers. Check that there is no loosening, bending, or detachment of the actuator linkages and pins. Verify that the opening indication shown on the DCS matches that observed locally. For electric valves with an intermediate stop function, ensure that this intermediate stop function operates properly. The direction of operation of the control valve should be correct, and it should move smoothly. For valves equipped with interlock circuits, interlock tests must be carried out in conjunction with the relevant technical teams. The pneumatic control device should also operate smoothly, without any air leaks or abnormal phenomena. If any abnormalities occur during the testing process, the test should be stopped immediately, and maintenance personnel should be notified to handle the issue. 2. Each time the unit is started up, operations must be carried out strictly in accordance with the “Operation Ticket”. All drain and vent valves must be checked and closed as prescribed. Six hours after all such valves have been closed (within 10 hours), for valves equipped with temperature indicators downstream thereof, it is necessary to analyze and determine whether there is any internal leakage based on the temperature readings of the pipes downstream of the valves. For valves lacking such temperature indicators, an infrared thermometer should be used to measure the pipe wall temperatures before and after the valves, or tactile inspection can be employed to determine whether internal leakage has occurred. If there is internal leakage in electric or pneumatic valves, the manual isolation valve located in front of the steam trap electric or pneumatic valve should be closed. In cases where there is no manual isolation valve in front of such valves, and the internal leakage is severe, the electric valve should be manually shut down, and maintenance should be requested to address the issue. If there is internal leakage in a manual door, record the issue and contact maintenance for repair. 3. Before shutting down the unit each time, a thorough inspection of the valves for any defects (leaks) should be carried out; valves with leaks should be recorded and the relevant maintenance department informed. 4. During startup, shutdown, or the process of draining water under pressure, once the drain valve is opened, it is necessary to check whether there is any temperature behind the valve or throttle orifice (desuperheater) to ensure that it functions properly for drainage. This helps to prevent corrosion caused by water accumulation in the thermal pipelines due to blockages in the valves, pipes, or throttle orifices (desuperheaters).