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    What's Valve
    time:2011-07-07  |  visits:402  |  tags:valve,,,
    Detail:

    Valve is one device for controlling the flow direction, pressure and flow rates in flow system. Valve is one device makes the medium into the piping and equipment (liquid, gas, powder) flow or stop, and even more control the medium flow rates.
    Valve can be divided into various types according to different functions.
    1. According to valve functions
    a) Cut-off valve: cut-off valve is also called as closing valve, cut-off valve function is connecting and cutting off the medium in the pipe. Cut-off valve includes gate valve, globe valve, plug valve, ball valve, butterfly valve and diaphragm valve.
    b) Check valve: check valve is also called as non-return valve, check valve function is preventing of the medium back flow in the pipe. The foot valve on the pump suction pipe is also check valve.
    c) Safety valve: safety valve function is preventing the medium pressure in the pipe and equipment from exceeding the set ones, in order to achieve the purpose of protecting the pipe and equipment.
    d) Regulating valve: regulating valve includes control valve, throttle valve and reducing valve, regulating valve function is regulating the medium pressure, flow, etc.
    e) Diverter valve: diverter valve includes various distributing valves and traps; diverter valve function is distributing, separating or mixing the medium in the pipe.
    2. According to valve nominal pressure
    a) Vacuum valve: vacuum valve working pressure is lower than standard atmospheric pressure.
    b) Low pressure valve: low pressure valve nominal pressure is ≤1.6Mpa.
    c) Middle pressure valve: middle pressure valve nominal pressure is 2.5, 4.0, 6.4MPa.
    d) High pressure valve: high pressure valve nominal pressure is 10~80MPa.
    e) Excess high pressure valve: excess high pressure valve nominal pressure is ≥100Mp.
    3. According to valve working temperature
    a) Ultralow temperature valve: ultralow temperature valve medium working temperature is <-100鈩.
    b) Cryogenic valve: cryogenic valve medium working temperature is -100鈩儈-40鈩.
    c) Normal temperature valve: Normal temperature valve medium working temperature is -40鈩儈120鈩.
    d) Intermediate temperate valve: intermediate temperate valve medium working temperature is 120鈩.
    e) High temperature valve: high temperature valve medium working temperature is >450鈩.
    4. According to valve operating
    a) Automatic valve: automatic valve does not need external force driving, but depends on the medium self energy to drive the valve action. Such as safety valve, reducing valve, trap, check valve and self-regulating valve.
    b) Power driven valve: power driven valve depends on various types of power to drive the valve. Motorized valve depends on the electric drive; pneumatic valve depends on the compressed air drive; hydraulic valve depends on the oil or other liquids pressure drive.
    c) Manual valve: manual valve depends on the hand wheel, handle, lever, chain wheel to operate the valve by manual labor. When valve on-off torque is big, there need mount gear or worm reducer between hand wheel and stem.
    5. According to valve nominal diameter
    a) Small-sized valve: small-sized valve nominal diameter is ≤40mm
    b) Middle-sized valve: middle-sized valve nominal diameter is 50~300mm
    c) Large-sized valve: large-sized valve nominal diameter is 350~120mm
    d) Extra big-sized valve: extra big-sized valve nominal diameter is ≥1400mm
    6. According to valve structure
    a) Stop valve: stop valve on-off part (disc) lift movement is driven by stem along the stop valve seat center line.
    b) Wedge valve: wedge valve on-off part (gate) lift movement is driven by stem along the center line that’s perpendicular to valve seat center line.
    c) Plug valve: plug valve on-off part (plug or ball) turns around them.
    d) Swing valve: swing valve on-off part (disc) turns around the shaft outside the valve seat.
    e) Butterfly valve: butterfly valve on-off part (plate) turns around the fixed shaft in the valve seat.
    f) Slide valve: slide valve on-off part slides along the direction that’s perpendicular to flow port.
    7. According to valve ends connection
    a) Threaded end valve: threaded end valve body has male threads or female threads connected with pipe threads.
    b) Flanged end valve: flanged end valve body has flanges connected with pipe flanges.
    c) Welded end valve: welded end valve body has welding groove connected with pipe welding groove.
    d) Clamp end valve: clamp end valve body has clip connected with pipe clamp.
    e) Wafer end valve: wafer end valve is connected directly with two ends pipes.
    8. According to valve materials
    a) Metal material valve: metal material valve body and other parts are made of metal materials, such as cast iron valve, carbon steel valve, alloy steel valve, copper alloy valve, aluminum alloy valve, lead alloy valve, titanium alloy valve and Monel metal valve.
    b) Nonmetal material valve: nonmetal material valve body and other parts are made of nonmetal materials, such as plastic valve, ceramic valve, enamel valve and glass steel valve.
    c) Metal body lining valve: Metal body lining valve body is metal while all the wetted parts are lining, such as rubber lined valve, plastic lined valve and ceramic lined valve.
    From the above, we can see there are many types of valves, but normally there are 11 types of valves, such as gate valve, globe valve, plug valve, ball valve, butterfly valve, diaphragm valve, check valve, throttling valve, safety valve, reducing valve and trap. 

     
       
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