The valve body is a main part of the valve; there are different mechanical manufacturing methods according to the pressure level. For example: casting, forging, etc. The valve body of medium and low pressure specification is usually produced by casting process. The medium and high pressure valve body is produced by forging process. It can effectively bear the medium pressure after being sealed together with valve core and valve seat sealing ring. The material of valve body shall be different metal materials according to different process media. Common materials are: cast iron, cast steel, stainless steel, carbon steel, etc.
Definition, function and application classification of valve body
1. Definition of valve body: valve is a device used to control the direction, pressure and flow of fluid in the fluid system. The valve is a device that makes the medium (liquid, gas, powder) in the piping and equipment flow or stop, and can control its flow.
2. According to the different functions of the opening and closing valves, there are many kinds of valve classification methods. Here are the following.
I. classification by function and use:
(1) block valve: block valve, also known as closed-circuit valve, is used to connect or block the medium in the pipeline. Block valves include gate valve, globe valve, plug valve, ball valve, butterfly valve and diaphragm.
(2) check valve: check valve is also known as one-way valve or check valve. Its function is to prevent the backflow of medium in the pipeline. The bottom valve of water pump 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 valve: the regulating valves include regulating valve, throttle valve and pressure reducing valve, whose function is to regulate the pressure, flow and other parameters of the medium.
(5) diverter valve: diverter valves include various distribution valves and drain valves, whose function is to distribute, separate or mix the medium in the pipeline.
II. Classification by operating temperature:
(1) ultra low temperature valve: used for the valve with medium working temperature T - 100 ℃.
(2) low temperature valve: used for the valve with medium working temperature of - 100 ℃ ≤ t ≤ - 40 ℃.
(3) normal temperature valve: used for the valve with medium working temperature - 40 ℃ ≤ t ≤ 120 ℃.
(4) medium temperature valve: used for medium working temperature 120 ℃
(5) high temperature valve: used for the valve with medium working temperature T 450 ℃.
3. Classification by structural features:
(1) closure shape: the opening and closing parts (disc) are driven by the valve stem to move up and down along the center line of the valve seat;
(2) plug shape: the opening and closing parts (gate valves) are driven by the valve stem to move up and down along the center line perpendicular to the valve seat;
(3) plug valve: the opening and closing parts (cone plug or ball) rotate around their own center line;
(4) swing valve: the hoist (disc) rotates around the shaft outside the seat;
(5) Butterfly: the hoist (disc) rotates around the fixed axis in the valve seat;
(6) slide valve travel: the opening and closing parts slide in the direction perpendicular to the channel.
IV. classification by connection method:
(1) threaded connection valve: the valve body is provided with internal thread or external thread, which is connected with pipeline thread. (2) flange connected valve: the valve body is equipped with flange, which is connected with the pipeline flange.
(3) welded connection valve: the valve body is provided with a welding groove, which is welded to the pipeline.
(4) clamp connection valve: the valve body is provided with a clamp, which is connected with the pipe clamp.
(5) ferrule connecting valve: the valve is connected with the pipeline by ferrule.
(6) wafer connection valve: the connection mode of directly threading the valve and two end pipes together with bolts.
V. classification by valve body material:
(1) metal material valve: the 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, Monel alloy valve, etc.
(2) non metallic material valve: its valve body and other parts are made of non-metallic material. Such as plastic valve, ceramic valve, enamel valve, FRP valve, etc.
(3) metal valve body lined valve: the valve body is metal in shape, and the main surfaces in contact with the medium are lined, such as rubber lined valve, plastic lined valve, ceramic lined valve, etc.
Vi. classification by driving mode:
(1) automatic valve refers to the valve that does not need external force to drive, but relies on the energy of the medium itself to make the valve act. Such as safety valve, pressure reducing valve, drain valve, check valve, automatic control valve, etc.
(2) power driven valve: the power driven valve can be driven by various power sources. Electric valve: valve driven by electricity. Pneumatic valve: valve driven by compressed air. Hydraulic valve: valve driven by liquid pressure such as oil. In addition, there are several combinations of the above driving modes, such as gas electric valve, etc.
(3) manual valve: manual valve is operated manually by hand wheel, handle, lever and sprocket. When the opening and closing torque of the valve is large, this wheel or worm gear reducer can be set between the hand wheel and the valve rod. If necessary, the universal joint and transmission shaft can also be used for remote operation. To sum up, there are many classification methods for valves, but they are mainly classified according to their functions in pipelines. General purpose valves in industrial and civil engineering can be divided into 11 categories, namely gate valve, stop valve, plug valve, ball valve, butterfly valve, diaphragm valve, check valve, throttle valve, safety valve, pressure reducing valve and drain valve. Other special valves, such as valves for instrument, hydraulic control pipeline system, valves for various chemical mechanical equipment, etc., are not included in the scope of this book.
VII. Classification by nominal diameter:
(1) small diameter valve: valve with nominal diameter DN ≤ 40mm.
(2) medium diameter valve: valve with nominal diameter DN of 50-300 mm.
(3) large diameter valve: valve with nominal valve DN of 350-1200mm.
(4) oversize valve: valve with nominal diameter DN ≥ 1400mm.
VIII. Classification by nominal pressure:
(1) vacuum valve: refers to the valve whose working pressure is lower than the standard atmospheric pressure.
(2) low pressure valve: refers to the valve with nominal pressure PN ≤ 1.6Mpa.
(3) medium pressure valve: refers to the valve with nominal pressure PN of 2.5, 4.0 and 6.4Mpa.
(4) high pressure valve: refers to the valve with a pressure PN of 10-80mpa.
(5) ultra high pressure valve: refers to the valve with nominal pressure PN ≥ 100MPa.