Valve is a device used to control the direction, pressure and flow of the fluid in the fluid system. It is a device that makes the medium (liquid, gas, powder) flow or stop in the piping and equipment and can control its flow. The valve is an important control component in the fluid transportation system.
Preparation before operation
Read the operating instructions carefully before operating the valve. Before operation, the flow direction of gas must be clear, and the valve opening and closing signs should be checked. Check the appearance of the valve to see if it is damp. If it is damp, it should be dried; if there is any other problem, it should be handled in time, and no fault operation is allowed. If the electric valve has been stopped for more than 3 months, the clutch should be checked before starting, and the insulation, steering and electrical circuit of the motor should be checked after confirming that the handle is in the manual position.
Correct operation method of manual valve
Manual valve is the most widely used valve, its hand wheel or handle is designed according to the ordinary manpower, considering the strength of the sealing surface and the necessary closing force. Therefore, long lever or long spanner can not be used to move. Some people are used to using spanner, and should pay close attention to it. When opening the valve, the force should be stable to avoid excessive force, causing the valve to open and close. The force should be stable and not impact. Some parts of high-pressure valves with impact opening and closing have considered that the impact force is not equal to that of general valves.
When the valve is fully opened, the handwheel should be reversed a little to make the threads tight to avoid loosening and damage. For rising stem valves, remember the position of the stem when fully open and fully closed, so as to avoid hitting the top dead center when fully open. It is convenient to check whether it is normal when fully closed. If the valve does fall off, or valve core seal between the embedded larger debris, fully closed valve stem position will change. Valve sealing surface or handwheel damage.
Valve opening sign: when the groove on the top surface of the valve stem of ball valve, butterfly valve and plug valve is parallel to the channel, it indicates that the valve is in the full open position; when the valve stem is rotated to the left or right by 90. The groove is perpendicular to the channel, indicating that the valve is in the fully closed position. Some ball valve, butterfly valve, plug valve with wrench and channel parallel to open, vertical for close. The operation of three-way and four-way valves shall be carried out according to the marks of opening, closing and reversing. Remove the movable handle after operation.
Correct operation method of safety valve
The safety valve has passed the pressure test and constant pressure before installation. When the safety valve runs for a long time, the operator should pay attention to check the safety valve. During the inspection, people should avoid the safety valve outlet, check the lead seal of the safety valve, pull up the safety valve with a wrench by hand, open it once at an interval to remove dirt and verify the flexibility of the safety valve.
Correct operation method of drain valve
Drain valve is easy to be blocked by water and other debris. When it is started, first open the flushing valve and flush the pipeline. If there is a bypass pipe, the bypass valve can be opened for short-term flushing. For the drain valve without flushing pipe and bypass pipe, the drain valve can be removed. After opening the cut-off flushing, close the shut-off valve, install the drain valve, and then open the cut-off valve to start the drain valve.
Correct operation of pressure reducing valve
Before starting the pressure reducing valve, the bypass valve or flushing valve should be opened to clean the dirt in the pipeline. After the pipeline is flushed, the bypass valve and flushing valve shall be closed, and then the pressure reducing valve shall be started. There is a drain valve in front of some steam pressure reducing valve, which needs to be opened first, then slightly open the shut-off valve behind the pressure reducing valve, and finally open the cut-off valve in front of the pressure reducing valve. Then, watch the pressure gauges before and after the pressure reducing valve, and adjust the adjusting screw of the pressure reducing valve to make the pressure behind the valve reach the preset value. Then slowly open the shut-off valve behind the pressure reducing valve to correct the pressure behind the valve until it is satisfactory. Fix the adjusting screw and cover the protective cap. For example
If the pressure reducing valve fails or needs to be repaired, the bypass valve should be opened slowly, and the cut-off valve in front of the valve should be closed at the same time. The bypass valve should be roughly adjusted manually to make the pressure behind the pressure reducing valve basically stable at the predetermined value. Then close the pressure reducing valve, replace or repair it, and then return to normal.
Correct operation of check valve
In order to avoid the high impact force formed at the moment when the check valve is closed, the valve must be closed quickly, so as to prevent the formation of great backflow velocity, which is the cause of impact pressure when the valve is suddenly closed. Therefore, the closing speed of the valve should match the attenuation rate of the downstream medium correctly.
If the velocity range of downstream medium is large, the minimum velocity is not enough to force the closure to stop stably. In this case, the movement of the closing part can be restrained by a damper within a certain range of its action stroke. The rapid vibration of the closing parts will make the moving parts of the valve wear too fast, leading to premature failure of the valve. If the medium is pulsating flow, the rapid vibration of the closing part is also caused by extreme medium disturbance. In this case, the check valve should be placed at the place where the medium disturbance is the least.
Post time: Apr-06-2021