The valve is the control device of the fluid pipeline. Its basic function is to connect or cut off the flow of the medium in the pipeline, change the flow of the medium, change the flow direction of the medium, adjust the pressure and flow of the medium, and protect the normal operation of the equipment in the pipeline.
The large-scale application of industrial valves is after Watt invented the steam engine. In the past 20 to 30 years, due to the needs of petroleum, chemical industry, power station, metallurgy, shipbuilding, nuclear energy, aerospace and other aspects, higher requirements have been placed on valves, prompting people to study And the production of high-parameter valves, the working temperature ranges from ultra-low temperature -269 °C to high temperature 1200 °C, even as high as 3430 °C, the working pressure ranges from ultra-vacuum 1.33x10-8Mpa (1x10-1㎜Hg) to 1460MPa, and the valve diameter ranges from 1mm to 600mm, even up to 9750mm, the material of the valve has developed from cast iron, carbon steel to titanium and titanium alloys, high-strength corrosion-resistant steel, etc. The driving method of the valve has developed from manual to electric, pneumatic, hydraulic, program-controlled, numerical control, remote control, etc. .
With the continuous development of modern industry, the demand for valves continues to increase. A modern petrochemical plant needs tens of thousands of various valves, and the valve usage is large. Frequent opening and closing, but often due to improper manufacture, use, selection, and maintenance, the phenomenon of running, running, dripping, and leaking occurs, resulting in fire, explosion, poisoning, and scalding accidents, or resulting in poor product quality, increased energy consumption, and equipment corrosion. , the increase of material consumption, environmental pollution, and even accidents such as production stoppage are not uncommon. Therefore, people hope to obtain high-quality valves, but also require to improve the use and maintenance level of valves. At this time, valve operators, maintenance personnel and engineering technicians , put forward new requirements, in addition to careful design, reasonable selection, and correct operation of the valve, but also timely maintenance and repair of the valve, so that the valve "running, running, dripping, leaking" and various accidents are reduced to the limit.