What should be paid attention to in manual valve operation?
Manual valve operation and precautions in operation:
The correct operation of the valve directly affects the service life, which is related to the smooth production of equipment and devices, and even the safety of the entire system.
Manual valves are operated by handles and handwheels. Its rotation direction is clockwise to close and counter-clockwise to open. But there are also some valves that open the opposite of the above. Therefore, you should pay attention to checking the opening and closing signs before operation.
Handwheels, handles are opened or closed by the operator with the aid of levers and long wrenches out of sequence. Some operators think that the higher the closing force, the better, but in fact this can cause premature valve damage and even an accident.
Valves such as gate valves and globe valves should be turned 1/2 to 1 turn when they are closed or opened to the limit of effective stroke, so that the threads are more tightly fitted, which is conducive to inspection during operation, so as to avoid over-tightening and damage to the valve parts.
Butterfly valve, gate valve and globe valve with larger diameter, some have bypass valve, its function is to preheat the pipeline and balance the pressure difference between inlet and outlet, and reduce the opening force. When opening, the bypass valve should be opened first, and the large valve should be opened after the pressure difference between the two sides of the valve is reduced. When closing the valve, first close the bypass valve, and then close the large valve.
When opening the valve of the steam medium, the pipeline must be preheated to remove the condensed water. When opening and closing the valve, it should be carried out slowly to avoid water hammer and damage to the valve and equipment.
When the ball valve, butterfly valve and plug valve are opened, when the groove on the top surface of the valve stem is parallel to the channel, it indicates that the valve is fully open again; when the valve stem rotates 90° to the left or right, the groove is perpendicular to the channel, indicating that the valve is in the fully open position. fully closed position. Some ball valves, butterfly valves and plug valves are opened with the wrench parallel to the channel, and closed vertically. The operation of the three-way and four-way valves should be carried out according to the marks of opening, closing and reversing. After the operation is completed, the movable handle should be removed.
For gate valves and throttle valves with scales, the fully open or fully closed indicating position should be checked and debugged. The rising stem gate valve and globe valve should also remember their fully open and fully closed positions, so as to avoid hitting the dead point when fully open. When the valve is fully closed, you can use the ruler and mark to find that the closing part falls off or resists foreign objects, which should be eliminated for troubleshooting.
When operating the valve, the gate valve, globe valve and other valves cannot be used as throttle valves, which will easily erode the sealing surface and cause the valve to be damaged prematurely.
The newly installed pipes, equipment and valves have a lot of debris such as dirt and welding slag, and the sealing surface of normally open valves is also prone to dirt. Close gently. After several times of opening and closing slightly, it can be washed clean.
After some valves are closed, the temperature drops and the valve parts shrink, resulting in small gaps on the sealing surface and leakage. In this way, the valve should be closed again at an appropriate time after closing the valve.