2. classification by nominal pressure(1) vacuum valve: refers to the working pressure is lower than the standard atmospheric pressure valve.(2): refers to the low pressure valve nominal pressure PN valve is less than 1.6Mpa.(3) medium pressure valve: refers to the nominal pressure PN 2.5, 4, 6.4Mpa valve.(4) high pressure valve: refers to the pressure valve PN is 10 ~ 80Mpa valve.(5) ultra high pressure valve: refers to the nominal pressure PN = 100Mpa valve.3. classification by operating temperature(1): ultra-low temperature valve for medium temperature valve T<100 C.(2): used for medium temperature valve operating temperature of 100 DEG C = t = 40 C valve.(3): valve used for medium temperature of-40 DEG C = t = 120 DEG C valve.(4) medium temperature valve: used for medium working temperature of 120 degrees(5) high temperature valve: valve used for medium temperature t>450 degrees celsius.
Two, according to the role of opening and closing valves, valve classification methods are many, here describes the following.1. classification by function and use(1) cut-off valve: cut off valve, also known as closed circuit valve, whose role is to connect or cut off the pipeline medium. The cut-off valve includes gate valve, globe valve, plug valve, ball valve, butterfly valve and diaphragm.(2) check valve: check valve, also known as one-way valve or check valve, its role is to prevent the medium back in the pipeline. Pump water off the bottom valve check valve also belongs to class.(3) safety valve: the role of the safety valve is to prevent the pipe or device in the medium pressure exceeds the required value, so as to achieve the purpose of safety protection.(4): regulating valve regulating valves including control valve, throttle valve and pressure relief valve, and its role in the regulation of the medium pressure, flow parameter.(5) shunt valve: diverter valve, including a variety of distribution valves and traps, etc., its role is to distribute, separate or mix the medium in the pipeline.
4. classification by drive(1) automatic valve refers to the valve does not require external force driven, but rely on the energy of the media itself to make the valve action. Such as safety valve, pressure reducing valve, steam trap, check valve, automatic control valve, etc..(2) power driven valve: power driven valve can be driven by a variety of power sources.Electric valve: electric drive valve.Pneumatic valve: driven by compressed air valve.Hydraulic valve: a valve actuated by liquid pressure such as oil.In addition, there are several combinations of driving methods, such as pneumatic electric valve.(3) manual valve: manual valve with hand wheel, handle, lever, chain wheel, by manpower to control valve action. When the valve opening and closing torque is larger, you can set the wheel or worm valve between the wheel or worm gear reducer. When necessary, the universal joint and the transmission shaft can also be used for long-distance operation.To sum up, the valve classification method is a lot of, but mainly in accordance with its role in the pipeline classification. Industrial and civil engineering general valve can be divided into 11 categories, namely, gate valve, globe valve, plug valve, ball valve, butterfly valve, diaphragm valve, check valve, throttle valve, safety valve, relief valve and drain valve. Other special valves, such as instrument valves, hydraulic control piping systems, valves, all kinds of chemical machinery, equipment, valves and so on, are not within the scope of this book.
First, the definition of valve:"Valve" is defined in the fluid system, used to control the direction of the fluid, pressure, flow device. A valve is a device for flowing or stopping the medium (liquid, gas, powder) in a pipe and equipment and controlling its flow.
