Detailed method for correct operation of valves II

Correct operation of safety valve

The safety valve has undergone pressure test and constant pressure before installation. When the safety valve runs for a long time, the operator shall pay attention to the inspection of the safety valve. During the inspection, the operator shall avoid the outlet of the safety valve, check the lead seal of the safety valve, pull up the safety valve with a wrench by hand, and open it once in a period of time to discharge the dirt and check the flexibility of the safety valve.

Correct operation method of drain valve

Drain valve is easy to be blocked by water pollution and other sundries. When it is used, first open the flushing valve and flush the pipeline. If there is a bypass pipe, the bypass valve can be opened for short flushing. For the drain valve without flushing pipe and bypass pipe, the drain valve can be removed. After opening the shut-off flushing, close the shut-off valve, install the drain valve, and then open the shut-off valve to enable the drain valve.

Correct operation of pressure reducing valve

Before the pressure reducing valve is opened, the bypass valve or flushing valve shall be opened to clean the dirt in the pipeline. After the pipeline is cleaned, the bypass valve and flushing valve shall be closed, and then the pressure reducing valve shall be opened. Some steam pressure reducing valves have drain valves in front of them, which need to be opened first, then slightly open the cut-off valve behind the pressure reducing valve, finally open the cut-off valve in front of the pressure reducing valve, watch the pressure gauge in front of and behind the pressure reducing valve, adjust the regulating screw of the pressure reducing valve to make the pressure behind the valve reach the predetermined value, then slowly open the cut-off valve behind the pressure reducing valve, and correct the pressure behind the valve until it is satisfied. Fix the adjusting screw and cover the protective cap.

If the pressure reducing valve fails or needs to be repaired, slowly open the bypass valve first, close the front shut-off valve at the same time, roughly adjust the bypass valve manually, so that the pressure behind the pressure reducing valve is basically stable at the preset value, and then close the pressure reducing valve for replacement or repair, and then return to normal.

Correct operation of check valve

In order to avoid the high impact force at the moment when the check valve is closed, the valve must be closed quickly to prevent the formation of a great backflow speed, which is the reason for the formation of impact pressure when the valve is suddenly closed. Therefore, the closing speed of the valve should be correctly matched with the attenuation speed of the downstream medium. 

If the velocity of the downstream medium varies widely, the minimum velocity is not enough to force the closure to stop stably. In this case, the motion of the closing member can be restrained by a damper within a certain range of its action stroke. The fast vibration of the closing parts will cause the valve moving parts to wear too fast, leading to premature failure of the valve. If the medium is pulsating flow, the fast vibration of the closing part is also caused by extreme medium disturbance. In any case, the check valve should be placed at the place with the least medium disturbance.

Post time: Mar-16-2020

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