Valve is in the fluid system, used to control the direction of the fluid, pressure, flow device is to make the pipe and equipment in the medium (liquid, gas, powder) flow or stop and can control the flow of the device, valve is an important control component in the fluid transport system.

Preparation before operation
Read the instructions carefully before operating the valve. The flow direction of gas must be clear before operation, and attention should be paid to check the opening and closing sign of the valve. Check the appearance of the valve to see whether the valve is damp, if there is damp to dry treatment; If other problems are found, they should be handled in a timely manner. If the electric valve is not used for more than 3 months, check the clutch before starting, confirm that the handle is in the manual position, and then check the insulation, steering and electrical circuit of the motor.

Correct operation of manual valve
The manual valve is the most widely used valve, and its hand wheel or handle is designed according to ordinary manual labor. The sealing surface strength and the necessary closing force are considered. So you can't use a long lever or a long spinner. Some people are used to using the wrench, should pay strict attention to, when opening the valve should be forced smoothly, avoid excessive force, resulting in the opening and closing of the valve, the force should be stable, not impact.The impact force of some high-pressure valve components has been considered and the general valve can not be equal.
When the valve is fully open, the hand wheel should be reversed a little, so that the thread between tight, so as not to loose damage. For pole-stem valves, remember the position of the stem when fully open and fully closed, to avoid hitting the top dead point when fully open.  And it is convenient to check whether it is normal when fully closed. If the valve does fall off, or between the spool seal embedded large debris, the position of the stem will change when fully closed.Damage to valve sealing surface or valve hand wheel.

Proper operation of pressure reducing valves
Before starting the pressure reducing valve, open the bypass valve or flush valve to clean the dirt in the pipeline. After the pipeline is cleaned, close the bypass valve and flush valve, and then start the pressure reducing valve.Before some of the steam pressure reducing valve, trap needs to open, then slightly open the cut-off valve after pressure reducing valve, finally the pressure reducing valve before the cut-off valve open, watch the pressure reducing valve and pressure gauge, adjust the relief valve adjusting screw, the valve after pressure to the expected value, then slowly open the shut-off valve after pressure reducing valve, valve after pressure correction, until satisfied.Fix the adjusting screw and cover the protective cap.
If the pressure reducing valve is faulty or repaired, the bypass valve should be opened slowly first, and the cut-off valve should be closed at the same time, and the bypass valve should be roughly adjusted manually, so that the pressure of the pressure reducing valve is basically stable at the predetermined value, and then the pressure reducing valve should be closed for replacement or repair, and then return to normal.
Correct operation of check valves
To avoid excessive impact force upon check valve closure, the valve must be closed quickly to prevent the extreme back flow velocity that is the cause of shock pressure when the valve is suddenly closed. Therefore, the closing speed of the valve should match the attenuation speed of the downstream medium correctly. 
If the velocity of the downstream medium varies widely, the minimum velocity is not enough to force the shutoff to stop steadily. In this case, the movement of the closing part can be suppressed by means of dampers within a certain range of its action stroke. The rapid vibration of the closing parts will make the valve moving parts wear too fast, resulting in premature failure of the valve. If the medium is pulsating, the rapid vibration of the shutoff is also caused by extreme medium disturbance. In this case, the check valve should be located where the medium disturbance is minimal.