The needle valve is a kind of adjustable valve, which has a wide range of uses, such as the cutting distance for flame cutting, and the knob for adjusting the flame temperature is the needle valve. The instrument needle valve is an important part of the instrument measuring pipeline system. It mainly includes a globe valve and a ball valve, and its function is to open or cut the pipeline path. The spool of a needle valve is a very pointed cone, inserted into the valve seat like a needle, hence the name.
Shut-off valves, also known as gate valves, are forced-sealed valves, so when the valve is closed, pressure must be applied to the clapper to force the sealing surface to not leak. When the medium enters the valve from below the valve flap, the resistance to be overcome by the operating force is the friction force between the stem and the packing and the thrust generated by the pressure of the medium. The diameter should be large, otherwise the failure to bend the valve stem will occur.
Installation Precautions
1. The installation position, height, and inlet and outlet directions must meet the design requirements. Note that the direction of the medium flow should be consistent with the direction of the arrow marked on the valve body, and the connection should be firm and tight.
2. The valve must be visually inspected before installation. The nameplate of the valve should comply with the provisions of the current national standard "General Valve Mark" GB 12220. For valves with a working pressure greater than 1.0 MPa and acting as a shut-off on the main pipe, strength and tightness performance tests should be carried out before installation, and qualified before use. During the strength test, the test pressure is 1.5 times the nominal pressure, the duration is not less than 5min, and the valve housing and packing should be qualified for no leakage. During the tightness test, the test pressure is 1.1 times the nominal pressure; the duration of the test meets the requirements of GB 50243.
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