Instructions for the operation and use of the valve

After the valve is installed, the operator can familiarize with the structure and performance of the valve and transmission device, correctly identify the opening direction, opening degree mark, indication signal, etc. of the valve, and can operate the valve skillfully and accurately, and timely and decisively handle each An emergency failure. The correct operation of the valve directly affects its service life and is related to the smooth and safe production of equipment and equipment.

Manual valve operation
Manual valves are operated by handwheels and handles. They are widely used in petrochemical plants. Operators should pay attention to the following points:
◆ The opening direction of the valve, usually counterclockwise to indicate that the valve is open, clockwise to indicate that the valve is closed. Therefore, pay attention to the direction when opening and closing the valve.
◆The handle of the valve, the size of the hand wheel is designed according to the valve manual switch. Therefore, the switch can be realized by manually turning the valve, and it is generally not allowed to open and close the valve by means of a lever or a wrench. In order to prevent excessive force, damage to sealing surfaces and other parts
◆When the closed gate valve and the shut-off valve are closed to the dead point, turn 1/4 turn to 1/2 turn to make the thread better tighter, so as not to overtighten and damage the valve
◆Do not use the gate valve or the stop valve for throttling, so it is easy to flush the valve plate and sealing surface, and introduce vibration leakage and damage the valve.
◆When the steam valve is opened, it should be slowly opened to remove the condensed water in the pipeline to prevent water hammer. Damage to valves and pipes
◆ Large-diameter gate valves, globe valves and butterfly valves, some with bypass valves, which balance the pressure on both sides of the valve and reduce the opening force. Therefore, when opening, the bypass valve should be opened first, then the valve should be opened slowly. When closing the valve, the bypass valve should be closed first, then the main valve should be closed slowly.
◆After some valves are closed, after the temperature drops, the valve member shrinks and the sealing surface shows a slight leakage. At this time, the valve should be closed after the valve is closed.

Automatic valve operation
◆Trap valve
Before being activated, the dirt and impurities in the pipeline should be discharged to prevent blockage by debris and malfunction. During operation, check the operation of the trap. If the steam is discharged too much, the valve is not working properly. If only the water is drained, the valve is working normally.
◆Safety valve
The safety valve shall be regularly subjected to constant pressure inspection, and the constant pressure record and mark shall be made. Before installation, it shall pass the pressure test and constant pressure test. In the past, safety valves were all off-line, and production units had a scientific management method. In recent years, some units have introduced safety valve online calibration instrument, which consists of mechanical, hydraulic and electronic records. The advantage is that the working conditions are more in line with the actual production, the data is more realistic, and can not affect the production, no need to disassemble And handling, and can improve the adjustment rate of the safety valve. The disadvantage is that it can only be used for spring safety valves, and the valve stem must be threaded; the average diameter of the valve sealing surface must be known; the safety valve cannot be cleaned, ground, replaced, and airtight tested. If the safety valve cannot return to the seat after the start of the jump, it will run a large amount of material and affect the production. Measures should be taken immediately for disposal. The method is to use a safety valve with a wrench on the hand plate, the gap is opened once for a period of time, and the dirt is drained.
◆Reducing valve
Open the bypass valve or flush valve cleaning pipe before starting. Close the bypass valve and activate the pressure reducing valve after the pipe is clean.

Operation of other valves
Other valves use electric, electromagnetic, pneumatic and hydraulic devices to open and close the valve. Remote control is achieved by means of meters and electric switches. Therefore, the operator should know in detail the structural characteristics and working principle of his moving valve, be familiar with the operating procedures, and be able to operate independently, and perform emergency treatment in the event of an accident.

Precautions in valve operation
◆ Prevent the valve from being staggered, misaligned, leaked, and leaked. The operator should clearly understand the role of each valve and the position in the process pipeline to prevent misuse, otherwise it may cause accidents such as running materials, mixing, and rolling. For example, in a refinery, steam is purged before the start of construction, and a vent valve is leaked after being purged. As a result, at 370 °C, the high temperature slurry is discharged from the vent valve, causing a fire and the installation device is shut down.
◆When the temperature is below 0 °C, the valve should be mainly antifreeze, and the plug at the bottom of the valve should be opened in time to discharge the condensation water inside. Keep warm for valves that cannot be excluded and work intermittently.
◆ For valves working at high temperature, when the temperature rises above 200 °C, the bolts are heated and elongated, which makes the valve seals not tight. When necessary, the bolts should be “hot tight”. When the heat is tight, it should not be carried out at the valve full close position. . In order to avoid the valve stem from dying, it is difficult to open again.
◆When the valve leaks, the leaking part and the cause should be firstly identified. Under normal circumstances, there are two kinds of internal leakage and external leakage. External leakage is divided into packing leakage and bonnet, valve body leakage and sealing surface or lining according to its external structure. If the material leaks, the operator should accurately judge that the problem that he can solve is to be dealt with in a timely manner.

◆The valve packing gland should not be pressed too tightly, so the valve stem can be flexibly rotated, and the pressure is too tight, which will increase the valve stem friction and increase the operating torque. When the valve is working, under normal circumstances, it is not possible to replace or add packing with any pressure. Otherwise, the leakage of the medium may cause danger.