How to Operate the Manual Valve Correctly?

Manual valve is a kind of valve that is commonly used on equipment and devices. It is operated by handle and hand wheel. In general, the clockwise rotation of the handle and handwheel is specified as the closing direction, and the counterclockwise rotation is specified as the opening direction. However, the opening and closing direction of some valves is opposite to the above, and the opening and closing signs should be checked before operation.

The size of the handle and hand wheel of the manual valve is designed according to normal people. Therefore, it is stipulated in the use of the valve: the operator is not allowed to open and close the valve with the help of a lever and a long wrench. At the same time, the handle length and the diameter of the handwheel are less than 320mm, only allowed to operate by one person; for the handwheel with a diameter equal to or more than 320mm, two people are allowed to operate together, or one person is allowed to operate with an appropriate lever (generally less than 0.5m in length). However, diaphragm valves and non-metal valves are strictly prohibited to operate with levers or long wrenches, and do not apply excessive force or force to close the valves.

Some operators are accustomed to using levers and long wrenches to operate manual valves, thinking that the greater the closing force, the better, but this is not the case. This will cause premature damage to the valve and even cause an accident. Practice has proved that, with the exception of the impact-type handwheel, operating the valve too aggressively can easily damage the handwheel and handle, scratch the valve stem and sealing surface, and even crush the sealing surface. Secondly, if the handwheel and handle are damaged or lost, they should be equipped in time, and an adjustable wrench should be used instead.

For valves such as gate valves and globe valves, when they are closed or opened to the end (ie bottom dead center or top dead center), they must be rotated 1/4 to 1/2 turn to make the threads more tightly, so as to facilitate the inspection during operation, so as not to twist Too tight to damage the valve.

Larger diameter butterfly valves, gate valves and stop valves, and some are equipped with bypass valves. The function of the bypass valve is to balance the pressure difference between the inlet and outlet and reduce the opening torque. When opening, the bypass valve should be opened first, and then the large valve should be opened.

Before opening the steam valve, the pipe must be preheated to discharge the condensed water. It should be opened slowly to avoid water hammer and damage the valve 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 passage, it indicates the full open position of the valve; when the valve stem is rotated 90 degrees to the left or right, when the groove is perpendicular to the passage, Indicates that the valve is in the fully closed position. Some ball valves, butterfly valves, and plug valves are opened with a wrench parallel to the channel, and closed when vertical. The operation of the three-way and four-way valves should be carried out according to the marks of opening, closing and reversing, and the movable handle should be removed after the operation is completed.

For gate valves and throttle valves with a mark, check and adjust the fully open or fully closed indication position. Rising stem gate valves and globe valves should also be used in fully open and fully closed positions, so as to avoid hitting the dead point when fully open. When the valve is fully closed, the ruler and mark can be used to find that the closing part falls off or resists the foreign body in order to troubleshoot.

The newly installed pipelines and equipment have many internal dirt and welding ballast. Dirt is easily stuck on the sealing surface of the normally open manual valve. Use the slightly open method to let the high-speed medium wash away these foreign objects, and then gently close it.

After some manual valves are closed, the temperature drops and the valve shrinks, causing small gaps on the sealing surface and leakage. In this way, it should be closed again at an appropriate time after it has been closed.

See the Sample:Manual valve

The correct operation of the valve directly affects the service life of the valve.

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