Classification of valves Industrial valves were born after the invention of the steam engine. In the past two to three decades, due to the needs of petroleum, chemical industry, power station, metallurgy, shipbuilding, nuclear energy, aerospace, etc., higher requirements have been put forward on valves, and people have studied And the production of high-parameter valves, the working temperature ranges from ultra-low temperature -269℃ to high temperature 1200℃, or even as high as 3430℃; working pressure ranges from ultra-vacuum 1.33×10-8Pa (1×10ˉ10mmHg) to ultra-high pressure 1460MPa; valve diameter ranges from 1mm to 6000mm, or even 9750mm. The materials of the valves have developed from cast iron and carbon steel to titanium and titanium alloy steel, as well as high-strength corrosion-resistant steel, low-temperature steel and heat-resistant steel valves. The drive mode of the valve developed from electric, pneumatic, hydraulic, to program control, air number, remote control, etc. The valve processing technology also ranges from ordinary machine tools to assembly lines and automatic lines. According to the different functions of opening and closing valves, there are many classification methods of valves. Here are the following. 1. Classification by function and purpose (1) Cut-off valve: Cut-off valve is also called closed-circuit valve, its function is to connect or cut off the medium in the pipeline. Block valves include gate valves, globe valves, plug valves, ball valves, butterfly valves and diaphragm valves. (2) Check valve: Check valve is also called one-way valve or check valve, its function is to prevent the medium in the pipeline from flowing back. The bottom valve of the pump to close the water is also a check valve. (3) Safety valve: The function of safety valve
is to prevent the medium pressure in the pipeline or device from exceeding the specified value, so as to achieve the purpose of safety protection. (4) Regulating valves: Regulating valves include regulating valves, throttle valves and pressure reducing valves, whose function is to regulate the pressure, flow and other parameters of the medium. (5) Diversion valve: Diversion valves include various distribution valves and traps, etc., whose function is to distribute, separate or mix the medium in the pipeline. 2. Classification by nominal pressure (1) Vacuum valve: refers to a valve whose working pressure is lower than the standard atmospheric pressure. (2) Low-pressure valve: refers to the valve with a nominal pressure PN ≤ 1.6Mpa. (3) Medium pressure valve: refers to the valve with nominal pressure PN of 2.5, 4.0, 6.4Mpa. (4) High-pressure valve: refers to the valve whose working pressure PN is 10～80Mpa. (5) Ultra-high pressure valve: refers to the valve with nominal pressure PN≥100Mpa. 3. Classification by working temperature (1) Ultra-low temperature valve: used for valves with medium working temperature tu003c-100℃. (2) Cryogenic valve: a valve used for medium working temperature -100℃≤t≤-40℃. (3) Normal temperature valve: used for valves with medium working temperature -40℃≤t≤120℃. (4) Medium temperature valve: used for medium working temperature 120℃ (5) High temperature valve: used for medium working temperature tu003e450℃ valve. 4. Classification by driving method (1) Automatic valve refers to a valve that does not require external force driving, but relies on the energy of the medium to make the valve actuate. Such as safety valves, pressure reducing valves, traps, check valves, automatic regulating valves, etc. (2) Power driven valve: Power driven valve can be driven by various power sources. Electric valve: A valve driven by electricity. Pneumatic valve: A valve driven by compressed air. Hydraulic valve: A valve driven by the pressure of liquids such as oil. In addition, there are combinations of the above several driving methods, such as pneumatic-electric valves. (3) Manual valve: Manual valve uses hand wheel, handle, lever, sprocket, and manpower to control valve action. When the valve opening and closing torque is large, this wheel or worm gear reducer can be set between the handwheel and the valve stem. If necessary, the universal joint and drive shaft can also be used for remote operation. In summary, there are many classification methods for valves, but they are mainly classified according to their role in the pipeline. The general valves in industrial and civil engineering can be divided into 11 categories, namely gate valves, globe valves, plug valves, ball valves, butterfly valves, diaphragm valves, check valves, throttle valves, safety valves, pressure reducing valves and traps. Other special valves, such as valves for instruments, valves for hydraulic control piping systems, and valves for various chemical machinery and equipment bodies, are not within the scope of this book. 5. Classification according to nominal diameter (1) Small diameter valve: valve with nominal diameter DN≤40mm. (2) Middle diameter valve: the valve whose nominal diameter DN is 50～300mm. (3) Large-diameter valves: valves whose nominal valve DN is 350～1200mm. (4) Extra-large diameter valve: Valve with nominal diameter DN≥1400mm. 6. Classification according to structural characteristics (1) Sectional door shape: the opening and closing parts (valve) are driven by the valve stem to move up and down along the center line of the valve seat; (2) Cock shape: the opening and closing parts (gate valve) are driven by the valve stem It moves vertically along the center line of the valve seat; (3) Plug valve: the opening and closing part (cone plug or ball) rotates around its own center line; (4) Swing valve: the opening and closing part (valve) surrounds the outside of the seat (5) Butterfly line: the opening and closing member (disc) rotates around the fixed axis in the valve seat; (6) Slide valve line: the opening and closing member slides in the direction perpendicular to the channel. 7. Classification according to the connection method (1) Threaded valve: The valve body has internal or external thread and is connected with the pipe thread. (2) Flange connection valve: The valve body has a flange and is connected with the pipeline flange. (3) Welding connection valve: The valve body has a welding groove and is welded to the pipeline. (4) Clamp connection valve: The valve body has a clamp, which is connected with the pipe clamp. (5) Ferrule connection valve: the ferrule is connected to the pipeline. (6) Wafer connection valve: a connection form that directly clamps the valve and the two pipes together with bolts.
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