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DMG-06-3C2-50 
DMG-04-3C60-21
DMG-01-3C4-1038
DMG-06-3C60-50
DMG-06-3C4-50
DMG-04-3C4-D21
DMG-04-3D2-21
DMG-01-2D2-10
TC1G-01-40
JT-02-100-11
JT-02-200-11
JT-02-35-11
JT-02-350-11
DSPG-01-C-D24-20
EHDFG-03-06-3C40-XY-30

Valves are devices within fluid systems that control the direction, pressure, and flow rate of fluids. They enable the flow or cessation of media (liquids, gases, powders) within piping and equipment while regulating their flow rate. Valves constitute vital control components in fluid conveyance systems.  
Preparations Prior to Operation  
Before operating valves, carefully review the operating instructions. Ensure the gas flow direction is clearly understood prior to operation. Pay attention to checking the valve open/close indicators. Inspect the valve externally for signs of moisture; if damp, dry thoroughly. Address any other issues promptly; never operate with faults present. For electric valves out of service for over three months, inspect the clutch before starting. Confirm the handle is in manual position, then check the motor insulation, rotation direction, and electrical wiring.   
Correct Operation of Manual Valves  
Manual valves are the most widely used type. Their handwheels or handles are designed for ordinary human strength, accounting for seal face strength and necessary closing force. Therefore, long levers or wrenches must not be used. Those accustomed to using wrenches should strictly note that when opening valves, force should be applied steadily and evenly, avoiding excessive force that could damage the valve. Force should be applied smoothly, without impact. Certain high-pressure valves engineered for impact operation incorporate components specifically designed to withstand such forces, differing fundamentally from standard valves.  
Upon fully opening the valve, slightly reverse the handwheel to ensure threaded connections are tightly engaged, preventing loosening and damage. For rising stem valves, memorise the stem position at both fully open and fully closed to avoid impact at the upper dead centre when fully open. This also facilitates verification of proper closure. Should the valve disc detach or significant debris become lodged between the valve core seals, the stem position at full closure will alter. This may indicate damage to the valve sealing surfaces or the valve handwheel.   
Valve open indication: For ball valves, butterfly valves, and plug valves, when the groove on the top surface of the valve stem is parallel to the passage, the valve is fully open. When the stem is rotated 90 degrees to the left or right, the groove becomes perpendicular to the passage, indicating the valve is fully closed. Some ball valves, butterfly valves, and plug valves indicate opening when the spanner is parallel to the passage and closing when perpendicular. Operation of three-way and four-way valves should follow the markings for opening, closing, and directional change. The removable handle should be detached after operation.

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