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How to operate manual valves correctly


Manual valve is a type of valve commonly used in equipment and devices, which is operated through a handle or handwheel. In general, clockwise rotation of the handle and handwheel is specified as the closing direction, and counterclockwise rotation is specified as the opening direction. But some valves have opposite opening and closing directions as mentioned above. Before operating, attention should be paid to checking the opening and closing signs before operating< br />
The size of the handle and handwheel of a manual valve is designed according to normal human factors. Therefore, in the use of valves, it is stipulated that operators are not allowed to use levers and long wrenches to open and close valves. If the length of the handle and the diameter of the handwheel are less than 320mm, only one person is allowed to operate; Handwheels with a diameter equal to or exceeding 320mm can be operated by two people together, or one person can use an appropriate lever (usually not exceeding 0.5m in length) to operate. However, diaphragm valves and non-metallic valves are strictly prohibited from being operated with levers or long wrenches, and excessive or forceful force should not be used to close the valve< br />
Some operators are accustomed to using levers and long wrenches to operate manual valves, believing that the greater the closing force, the better, but in fact, it is not. This can cause premature damage to the valve and even lead to accidents. Practice has proven that, except for the impact type handwheel, operating the valve too large or too forcefully can easily damage the handwheel and handle, scratch the valve stem and sealing surface, and even crush the sealing surface. Secondly, if the handwheel or handle is damaged or lost, it should be promptly equipped and should not be replaced with a live wrench< br />
Valves such as gate and globe valves should rotate 1/4 to 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 fitted and facilitate inspection during operation to avoid overtightening and damaging the valve< br />
Some butterfly valves, gate valves, and globe valves with larger diameters are equipped with bypass valves. The function of the bypass valve is to balance the inlet and outlet pressure difference and reduce the opening torque. When opening, the bypass valve should be opened first, and then the large valve should be opened< br />
Before opening the steam valve, the pipeline must be preheated to discharge the condensed water. Open slowly to avoid water hammer and damage to valves and equipment. When opening and closing ball valves, butterfly valves, and plug valves, when the groove on the top surface of the valve stem is parallel to the channel, it indicates the fully open position of the valve; When the valve stem is rotated 90 degrees to the left or right, and the groove is perpendicular to the channel, it indicates that the valve is in the fully closed position. Some ball valves, butterfly valves, and plug valves open when the wrench is parallel to the channel, and close when the wrench is vertical. The operation of 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< br />
For gate and throttle valves with a center mark, the fully open or fully closed indication position should be checked and adjusted. Rising stem gate valves and globe valves should also be in their fully open and fully closed positions to avoid hitting the dead center when fully open. When the valve is fully closed, it can be detected with the help of a ruler and markings that the closing part has fallen off or stuck against foreign objects, in order to troubleshoot< br />
Newly installed pipelines and equipment have a lot of dirt and welding slag on the inside. Dirt can easily stick to the sealing surface of a normally open manual valve. Use a slightly open method to allow high-speed media to wash away these foreign objects, and then gently close< br />
Some manual valves, after being closed, experience a decrease in temperature and shrinkage of the valve components, resulting in small gaps on the sealing surface and leakage. This should be done again at an appropriate time after closing< br />
The correct operation of the valve directly affects its service life