Basic knowledge of valve

The large number of applications of industrial valves came after Watt’s 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 power, aerospace, etc., higher requirements have been put on valves, prompting people to study And the production of high-parameter valves, its working temperature ranges from ultra-low temperature -269℃ to high temperature 1200℃, and even as high as 3430℃. The large number of applications of valves with working pressure from ultra-industrial use are after Watt invented the steam engine. The needs of petroleum, chemical industry, power station, metallurgy, shipbuilding, nuclear energy, aerospace, etc. put forward higher requirements on valves, prompting people to research and produce high-parameter valves. The working temperature ranges from ultra-low temperature -269℃ to high temperature 1200℃, and even Up to 3430℃, working pressure from ultra-vacuum 1.33x10-8Mpa (1x10-1mmHg) to ultra-high pressure 1460MPa, valve diameter from 1mm to 600mm, even up to 9750mm, the valve material has developed from cast iron, carbon steel to titanium and Titanium alloy, high-strength corrosion-resistant steel, etc., the drive mode of the valve has developed from manual to electric, pneumatic, hydraulic, program control, numerical control, remote control, etc.　　 With the continuous development of modern industry, the demand for valves continues to grow. A modern petrochemical plant needs tens of thousands of valves of all kinds, and the use of valves is large. Frequent opening and closing, but often due to improper manufacturing, use, selection, and maintenance, running, emitting, dripping, and leaking, which cause flames, explosions, poisoning, and scalding accidents, or cause poor product quality, increased energy consumption, and equipment corrosion , The increase in material consumption, environmental pollution, and even production stoppages are not uncommon. Therefore, people hope to obtain high-quality valves, and at the same time, they also need to improve the use and maintenance of valves. At this time, the To put forward new requirements, in addition to careful design, reasonable selection, and correct operation of the valve, it is also necessary to maintain and repair the valve in time to minimize the 'running, leaking, dripping, and leaking' of the valve and various accidents. 1. According to structural features, according to the direction of movement of the closing member relative to the valve seat, it can be divided into: 1. Sectional door shape: The closing piece moves along the center of the valve seat. 2. Gate shape: The closing piece moves along the center of the vertical valve seat. 3. Cock and ball: The closing piece is a plunger or ball, which rotates around its centerline. 4. Swing shape; the closing member rotates around the axis outside the valve seat. 5. Dish shape: The disc of the closing member, which rotates around the axis in the valve seat. 6. Sliding valve shape: The closing piece slides in a direction perpendicular to the channel. 2. According to the purpose, according to the different purposes of the valve can be divided into: 1. For breaking: used to connect or cut off pipeline media, such as globe valves, gate valves, ball valves, butterfly valves, etc. 2. Non-return use: used to prevent the medium from flowing back, such as a check valve. 3. Adjustment: used to adjust the pressure and flow of the medium, such as regulating valves and pressure reducing valves. 4. Distribution: used to change the flow direction of the medium and distribute the medium, such as three-way cock, distribution valve, slide valve, etc. 5. Safety valve: When the medium pressure exceeds the specified value, it is used to discharge excess medium to ensure the safety of the pipeline system and equipment, such as safety valves and emergency valves. 6. Other special purposes: such as traps, vent valves, drain valves, etc. 3. According to the driving mode, it can be divided according to different driving modes: 1. Manual: With the help of handwheel, handle, lever or sprocket, etc., it is driven by human power. When the transmission torque is large, it is equipped with worm gear, gear and other reduction devices. 2. Electric: Driven by motors or other electrical devices. 3. Hydraulic: driven by (water, oil). 4. Pneumatic; driven by compressed air. 4. According to the pressure, it can be divided according to the nominal pressure of the valve: 1. Vacuum valve: a valve whose absolute pressure is less than 0.1MPa, that is, 760mm mercury column, usually expressed in mm mercury column or mm water column. 2. Low pressure valve: valves with nominal pressure PN≤1.6MPa (including steel valves with PN≤1.6MPa) 3． Medium pressure valve: a valve with a nominal pressure of PN2.5-6.4MPa. 4. High-pressure valve: a valve with a nominal pressure of PN10.0-80.0MPa. 5. Ultra-high pressure valve: a valve with a nominal pressure of PN≥100.0MPa.