Operating specifications and precautions for manual valves
Manual valves are a type of valve commonly used in equipment and devices. They are operated by handles and handwheels. Generally speaking, the clockwise rotation of the handle and handwheel is designated as the closing direction, and the counterclockwise rotation is designated as the opening direction. However, the opening and closing direction of some valves is opposite to the above. Please check the opening and closing signs before operation. For manual valves, the size of the handle and handwheel are designed according to normal manpower. Therefore, operators are generally not allowed to use levers and long wrenches to open and close valves. It is strictly prohibited to use levers or long wrenches to operate diaphragm valves and non-metallic valves, and it is not allowed to use excessive or excessive force to close valves. The bellows cut-off door of the generator hydrogen system is prohibited from being operated with an F wrench and can only be operated manually. The pressure-reducing valve is a reverse valve, opening in the clockwise direction and closing in the counterclockwise direction. The quick closing door of the steam drum water level gauge must be fully open during operation to prevent the safety steel ball from being able to push against the valve seat joint surface when the water level gauge explodes and leaks, thereby failing to quickly and completely isolate the leakage point.
Specific requirements for valve operation
1. Gate valves and stop valves cannot be used as regulating valves to avoid erosion and wear that may cause the valves to be loose.
2. Two valves in series must be opened in order because the valve that opens later is affected; when closing, the secondary door must be closed first, then the primary door, etc.
3. When opening a valve with a small bypass, the small bypass door must be used to warm the pipe and equalize the pressure. After the main door is opened, the small bypass door should be closed.
4. If the valve is found to be loosely closed, it can be opened a small amount to allow the working fluid to flow through the valve for a while to wash away the impurities and then closed again.
5. Check the drain door frequently to ensure it is closed tightly. When operating the drain door, follow the sequence of opening and closing the valves in series. When opening and closing, you should pay attention: opening only one slit is more likely to wear due to the small flow area, so it should be opened as wide as possible.
6. If there is a slight leakage in the valve packing during operation, it should be discovered in time and the maintenance personnel should be notified in time to deal with it.
7. Valves such as gate valves and stop valves should be rotated 1/4~1/2 turn when closed or opened to the end (i.e. bottom dead center or top dead center) to make the threads more tightly sealed, which is beneficial for inspection during re-operation. To avoid over-tightening and damaging the valve.
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8. Do not use a large wrench (or sleeve) to help open small manual valves.
9. When opening and closing the valve, it should not be too tight to prevent damage to the valve.
10. Identify the valve switching direction: Generally, the manual valve is closed in the clockwise direction and open in the counterclockwise direction, and the opposite is true in some cases. There is a groove (mag line) on the top of the stem of the 90° turned plug valve, which is closed when it is perpendicular to the pipe and open when it is parallel to the pipe.
11. When there is a large temperature difference between the two sides of the valve, the warm pipe should be drained and opened slowly. If the valve has a bypass door, the bypass door should be opened first.
12. For pneumatic valves with a handwheel, the handwheel should be placed in the middle position (automatic position) under normal circumstances to avoid affecting the pneumatic action. When the pneumatic fails, it can be opened and closed by a hand wheel on the spot.
13. When operating the valve, you should stand on the side of the valve and be prepared for the evacuation path if the valve packing bursts.
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