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 body, powder) flow or stop and can control its flow device, valve is an important control part of the fluid delivery system.
Preparations before operation
Read the operating instructions carefully before operating the valve. Before operation, we must be clear about the gas flow direction, and should pay attention to check the valve opening and closing signs. Check the appearance of the valve to see if the valve is damp, if there is damp to dry treatment; If other problems are found, handle them in time and do not perform fault operations. If the electric valve is out of use 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 lines of the motor.
Proper operation of manual valves
Manual valve is the most widely used valve, its hand wheel or handle, is designed in accordance with ordinary manpower, considering the strength of the sealing surface and the necessary closing force. So you can't use long levers or long hands to move the board. Some people are used to using the plate hand, should pay strict attention to, open the valve should force and smooth, avoid excessive force, resulting in the opening and closing of the valve, force should be smooth, not impact. Some of the high pressure valve parts of the impact have taken into account the impact force and general valves can not be equal.
When the valve is fully opened, the handwheel should be reversed a little, so that the thread between the tight, so as not to loose damage. For open rod valves, remember the position of the valve stem when fully open and fully closed, to avoid hitting the top dead point when fully open. And easy to check whether the full closure is normal. If the valve is off, or large debris is embedded between the spool seal, the position of the valve stem should be changed when it is fully closed. Damage to valve sealing surface or valve handwheel.
Valve opening mark: ball valve, butterfly valve, plug valve stem top groove and channel parallel, indicating that the valve in the fully open position; When the stem is rotated 90 to the left or right. When the groove is perpendicular to the channel, indicating that the valve is in the fully closed position. Some ball valves, butterfly valves, plug valves with a wrench and channel flat behavior open, vertical closed. The operation of three-way and four-way valves should be carried out according to the marks of opening, closing and reversing. Remove the handle after operation.
Correct operation of safety valve
Safety valve in the installation before the pressure test, constant pressure. When the safety valve runs for a long time, the operator should pay attention to check the safety valve. During the check, people avoid the safety valve outlet, check the lead seal of the safety valve, pull up the safety valve with a wrench, open it once at intervals, remove dirt, and check the flexibility of the safety valve.
Proper operation of trap
The trap is easily blocked by water pollution and other debris valve. When enabled, first open the flushing valve, flushing pipe. If there is a by-pass pipe, the by-pass valve can be opened for short flushing. If there is no drain valve for washing pipe and bypass pipe, remove the drain valve, open and cut off the drain valve after washing, close the cut-off valve, install the drain valve, and then open the cut-off valve to enable the drain valve.
Correct operation of pressure reducing valve
Before using the reducing valve, open the bypass valve or flushing valve, clean the pipeline dirt, after cleaning the pipeline, close the bypass valve and flushing valve, and then start the reducing valve. Some steam reducing valve before the trap, need to open, and then slightly open the cutting valve after the reducing valve, finally open the cutting valve before the reducing valve, watch the pressure gauge before and after the reducing valve, adjust the regulating screw of the reducing valve, so that the pressure after the valve to reach a predetermined value, then slowly open the cutting valve after the reducing valve, correct the pressure after the valve, until satisfied. Secure the adjusting screws and cover the protective cap.
If the reducing valve is faulty or to be repaired, the by-pass valve should be opened slowly, and the valve should be cut off before closing the valve. The by-pass valve should be roughly adjusted manually, so that the pressure after the reducing valve is basically stable at the preset value, and then the reducing valve should be replaced or repaired and then restored to normal.
Correct operation of check valves
To avoid excessive impact force at the moment the check valve is closed, the valve must be closed quickly to prevent the extreme backflow velocity that is responsible for 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.
Given a wide range of velocity variations in the downstream medium, the minimum velocity is not sufficient to force the closure to stop stably. In this case, the motion of the closing member can be inhibited by a damper within a certain range of its operating stroke. The rapid vibration of the closing parts will make the movable parts of the valve wear too fast, resulting in premature valve failure. If the medium is pulsating flow, the rapid vibration of the closing part is also caused by extreme medium disturbance, where there is such a case, the check valve should be placed in the place where the medium disturbance is minimal.
