The size of the handle and hand wheel of the manual valve of Shanghai electric valve manufacturer is designed according to the normal proportion. Therefore, it is stipulated in the use of the valve: the operator is not allowed to open and close the valve with levers and long wrenches. At the same time, the handle length and the diameter of the handwheel are less than 320mm, only one person is allowed to operate; the handwheel with a diameter of 320mm or more allows two people to operate together, or allows one person to operate with an appropriate lever (generally less than 0.5m in length). However, diaphragm valves and non-metal valves are strictly prohibited to use levers or long wrenches to operate, nor are they allowed to close the valves with excessive force or force.
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. Experiments have proved that, with the exception of the impact-type handwheel, operating the valve too hard and too much 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 it is not allowed to use an adjustable wrench instead.
Manual valve is a kind of valve commonly used in equipment and devices, it is operated by handle and hand wheel. In general, the clockwise rotation of the handle and handwheel is defined as the closing direction, and the counterclockwise rotation is defined 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.
For valves such as gate valves and globe valves, when they are closed or opened to the end (bottom dead center or top dead center), they must be rotated 1/4 to 1/2 turn to make the threads tighter, so as to facilitate the inspection during operation and avoid twisting Too tight to damage the valve.
Larger diameter butterfly valves, gate valves and globe 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, open the bypass valve first, and then open the large valve.
Before opening the steam valve, the pipe must be preheated to discharge the condensed water. It must 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.
Generally, the flow rate of the valve is too high in the case of a small opening of the valve, and a vigorous turbulent vortex area will be formed behind the valve. The vortex area and the new pressure are very low. The pressure at this place is lower than the saturation pressure corresponding to the water temperature. Flashing causes the phenomenon of soda water hammer: severe noise, vibration of valves and pipes, damage to valves, pipes, and pipe supports. To prevent the occurrence of such accidents, first consider the valve plug and valve seat in the valve flow path design to form a long and narrow throttling channel to restrict the formation of strong turbulent vortex; secondly, when selecting valves, try to increase the valve power as much as possible. To avoid the valve from operating at a small opening. In addition, when the pressure conditions are not involved, try to install the alkali balance valve in the return water pipeline with lower water temperature.
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