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Correct operation method for different types of valves

Update:04-12-2020
Summary:

A valve is a device used to control the direction, pres […]

A valve is a device used to control the direction, pressure, and flow of fluid in a fluid system. It is a device that allows the medium (liquid, gas, powder) in the piping and equipment to flow or stop and can control its flow. The valve is a fluid delivery system An important control component in the

Preparation before operation

Before operating the valve, read the operating instructions carefully. Be sure to know the flow direction of the gas before operation, and check the valve opening and closing signs. Check the appearance of the valve to see if the valve is damp. If there is damp, it should be dried; if there are other problems, it should be dealt with in time, and no malfunction is allowed. If it is an electric valve that has been inactive for more than 3 months, check the clutch before starting. After confirming that the handle is in the manual position, check the motor insulation, steering and electrical wiring.

Correct operation method of manual valve

Manual valve is the most widely used valve. Its hand wheel or handle is designed according to ordinary manpower, taking into account the strength of the sealing surface and the necessary closing force. Therefore, you cannot use a long lever or a long wrench to move. Some people are accustomed to using wrenches, and they should be strictly careful. When opening the valve, they should use steady force to avoid excessive force that may cause the valve to open and close. The force should be steady and not impact. Some parts of high-pressure valves with impact opening and closing have considered that this impact force cannot be equal to that of general valves.

When the valve is fully opened, the handwheel should be turned upside down a little to tighten the threads to avoid loosening and damage. For rising stem valves, remember the valve stem positions when fully open and fully closed to avoid hitting the top dead center when fully open. And it is convenient to check whether it is normal when fully closed. If the valve stem falls off, or large debris is embedded between the valve core seal, the valve stem position will change when it is fully closed. Damage to the valve sealing surface or valve handwheel.

Valve opening sign: When the groove on the top surface of the valve stem of the ball valve, butterfly valve, and plug valve is parallel to the passage, it indicates that the valve is in the fully open position; when the valve stem rotates 90 left or right. When the groove is perpendicular to the channel, it indicates that the valve is in the fully closed position. Some ball valves, butterfly valves, and plug valves are opened with a wrench parallel to the channel and closed when vertical. The operation of three-way and four-way valves should be carried out according to the marks of opening, closing and reversing. The movable handle should be removed after the operation is completed.

 

 

Correct operation method of safety valve

The safety valve has undergone pressure test and constant pressure before installation. When the safety valve is running for a long time, the operator should pay attention to checking the safety valve. During the inspection, people should avoid the exit 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 at intervals. Drain the dirt and verify the flexibility of the safety valve.

Correct operation method of trap

A trap is a valve that is easily blocked by debris such as water and dirt. When enabled, first open the flush valve and flush the pipeline. If there is a bypass pipe, the bypass valve can be opened for short flushing. For traps without flushing pipes and bypass pipes, remove the traps, open the shut-off flushing, and then close the shut-off valve, install the trap, and then open the shut-off valve to activate the trap.

Correct operation method of pressure reducing valve

Before the pressure reducing valve is activated, the bypass valve or flushing valve should be opened to clean the pipeline dirt. After the pipeline is flushed, the bypass valve and the flushing valve should be closed, and then the pressure reducing valve should be activated. Some steam pressure reducing valves have traps in front of them, which need to be opened first, then slightly open the shut-off valve after the pressure reducing valve, and finally open the shut-off valve before the pressure reducing valve, watch the pressure gauges before and after the pressure reducing valve, and adjust the pressure reducing valve Adjust the screw to make the pressure after the valve reach a predetermined value, then slowly open the shut-off valve after the pressure reducing valve, and correct the pressure after the valve until you are satisfied. Fix the adjusting screw and cover the protective cap.

If the pressure reducing valve fails or needs to be repaired, first slowly open the bypass valve and close the shut-off valve in front of the valve. Manually adjust the bypass valve so that the pressure after the pressure reducing valve is basically stable at the predetermined value before closing. After the pressure reducing valve is replaced or repaired, it returns to normal.

Correct operation method of check valve

In order to avoid the excessively high impact force at the moment of closing of the check valve, the valve must be closed quickly to prevent the formation of a great reverse flow velocity, which is the cause of the 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 flow velocity is not sufficient to force the closure to stop stably. In this case, the movement of the closing member can be suppressed by a damper within a certain range of its movement stroke. The rapid vibration of the closing parts will wear the valve moving parts too fast, leading to premature valve failure. If the medium is a pulsating flow, the rapid vibration of the closing member is also caused by extreme medium disturbance. Whenever this situation exists, the check valve should be placed where the medium disturbance is minimal.

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