The manual valve is a control part of the pipeline fluid transmission system, which is used to change the channel section and the direction of the medium flow, with the functions of diversion, cut-off, regulation, throttling, check, shunt or overflow pressure relief. Valves for fluid control with nominal diameters ranging from very small instrument valves to industrial piping valves up to 10m in diameter.

First, the opening and closing of manual valves:

1, manual valve is the most widely used valve, its hand wheel or handle, is designed in accordance with ordinary manpower, considering the strength of the sealing surface and the necessary closing force. So you can't use long levers or long hands to move the board. Some people are used to using the plate hand, should strictly pay attention to, do not use too much force, otherwise it is easy to damage the sealing surface, or plate broken hand wheel, handle. 

2, open and close the valve, the force should be smooth, not impact. Some of the impact of the high pressure valve components have taken into account this impact force and general valves can not be equal. 

3, for the steam valve, before opening, should be heated in advance, and eliminate condensate, open, should be as slow as possible to avoid water shock phenomenon. 

4, when the valve is fully opened, the handwheel should be reversed a little, so that the thread between the tight, so as not to loose damage. For open-stem valves, remember the stem position when fully open and fully closed to avoid hitting the upper dead center when fully open. And easy to check whether the full closure is normal. If the valve is off, or large debris is embedded between the spool seal, the position of the valve stem should be changed when the valve is fully closed. 

5, when the pipeline is first used, the internal dirt is more, the valve can be slightly opened, the high-speed flow of the medium can be used to wash it away, and then gently closed (can not be fast closed, fast closed, to prevent residual impurities from hurting the sealing surface), open again, so repeated many times, wash the dirt, and then put into normal work. 

6, often open the valve, there may be dirt on the sealing surface, and it should be washed clean by the above method when closed, and then formally closed. 

7, such as the hand wheel, the handle is damaged or lost, should be immediately matched, can not be replaced by the flexible plate hand, so as to avoid damage to the valve stem square, opening and closing failure, resulting in accidents in production. 

8, some media, after the manual valve is closed to cool, so that the valve shrinkage, the operator should be closed again at the appropriate time, so that the sealing surface does not leave a fine seam, otherwise, the medium from the fine seam flow at high speed, it is easy to erode the sealing surface.

Second, precautions:

1, 200℃ above the high temperature valve, due to the installation at room temperature, and normal use, the temperature rises, the bolt is heated expansion, the gap increases, so it must be tightened again, called "hot tight", the operator should pay attention to this work, otherwise it is easy to leak. 

2, when the weather is cold, the water valve is closed for a long time, and the water after the valve should be removed. After the steam valve stops steam, condensate should also be removed. The bottom of the valve is like a silk plug, which can be opened to drain water. 

3, non-metallic valves, some hard and brittle, some low strength, operation, the opening and closing force can not be too large, especially can not make strong. Also pay attention to avoid objects bumping. 

4, when the new manual valve is used, the packing should not be pressed too tightly, so as not to leak, so as to avoid too much pressure on the valve stem, accelerate wear, and open and close laborious.