A brief history of the development of the hottest

2022-08-16
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A brief history of the development of valves and their types and uses

valves are devices used to control fluid flow, pressure and flow direction. The controlled fluid can be liquid, gas, gas-liquid mixture or solid-liquid mixture. The valve is usually composed of valve body, bonnet, valve seat, hoist, driving mechanism, seals and fasteners. The control function of the valve depends on the driving mechanism or fluid to drive the hoist to lift, slide, swing or rotate to change the size of the flow channel area

valves have a wide range of uses, which are closely related to people's daily life, such as faucets for tap water pipes and pressure reducing valves for LPG stoves. Valves are also indispensable components of various mechanical equipment, such as internal combustion engines, steam engines, compressors, pumps, pneumatic transmission devices, hydraulic transmission devices, vehicles, ships, etc. Two thousand years ago, the Chinese used bamboo pipes and wooden plug valves on water pipelines, and later used sluices on irrigation channels, plate check valves on bellows for smelting, and bamboo pipes and plate check valves to extract salt water in well salt mining. With the development of smelting technology and hydraulic machinery, copper and lead plug valves have appeared in Europe. With the use of boilers, lever hammer safety valves appeared in 1681. Before the advent of watt steam engine in 1769, plug valves and check valves were always the most important valves. The invention of steam engine has brought valves into the field of mechanical industry. In addition to plug valves, safety valves and check valves, butterfly valves are also used in Watt's steam engine to regulate flow. With the increase of steam flow and pressure, the use of plug valve to control the steam inlet and exhaust of steam engine can no longer meet the needs, so there is a slide valve. Around 1840, stop valves with threaded stems and wedge gate valves with trapezoidal threaded stems appeared successively, which was a major breakthrough in the development of valves. The emergence of these two types of valves not only met the requirements of various industries at that time for the continuous improvement of pressure and temperature, but also preliminarily met the requirements for flow regulation. Since then, with the development of power industry, petroleum industry, chemical industry and shipbuilding industry, various high and medium pressure valves have developed rapidly

after the Second World War, due to the polymer materials and lubrication, and the development of their utilization materials in medical devices, stainless steel and cobalt based cemented carbide, the ancient plug valves and butterfly valves obtained new applications, and ball valves and diaphragm valves developed rapidly. The variety and quality of stop valves, gate valves and other valves have been increased. Valve manufacturing industry has gradually become an important sector of the machinery industry. Valves can be divided into six categories according to their functions: block valve, regulating valve, check valve, diverter valve, safety valve and multipurpose valve. Block valves are mainly used to block fluid paths, including stop valves, gate valves, plug valves, ball valves, butterfly valves, diaphragm valves, pinch valves, etc; The regulating valve is mainly used to regulate the pressure and flow of fluid, including regulating valve, throttle valve, pressure reducing valve and floating ball regulating valve; The check valve is used to prevent the reverse flow of fluid; The diverter valve is used to distribute the path and direction of the fluid, or separate the two-phase fluid, including slide valve, multi-way valve, steam trap, air exhaust valve, etc; The safety valve is mainly used for safety protection to prevent the boiler, pressure vessel or pipeline from being damaged due to overpressure; Multi purpose valve is a valve with more than one function, such as stop check valve, which can not only cut off but also check. According to the nominal pressure, industrial pipeline valves can be divided into vacuum valve, low pressure valve, medium pressure valve, high pressure valve and ultra-high pressure valve; According to the working temperature, valves can be divided into normal temperature valve, medium temperature valve, high temperature valve and low temperature valve; Valves can also be classified according to the type of driving device, the connection mode with the pipeline and the material used in the valve body

valves can be named individually or in combination according to various classification methods, and can also be named according to the structural characteristics or specific uses of hoists The basic parameters of the valve are working pressure, working temperature and diameter. For various valves widely used in industrial pipelines, nominal pressure and nominal diameter are commonly used as basic parameters. Nominal pressure refers to the maximum allowable working pressure of a valve made of a certain material under the specified temperature. Nominal diameter refers to the nominal inner diameter of the connecting end of valve body and pipe. Valves have different requirements according to their types and uses, mainly including sealing, strength, regulation, circulation, opening and closing, etc. When designing and selecting valves, in addition to the basic parameters and performance, the performance of the fluid should also be considered, including the phase state of the fluid (gas, liquid or containing solid particles), corrosivity, viscosity, toxicity, flammability, rarity, radioactivity, etc. Sealing performance and strength performance are the most basic and important performance of all valves. The sealing of the valve is divided into internal sealing and external sealing. The inner seal is the seal between the valve disc and the valve seat; The outer seal is the seal between the moving part of the valve rod and the valve cover, between the valve body and the valve cover, and between the valve body and the connecting part of the pipeline. When the valve is used, it is required not only to have good sealing performance, but also to ensure safety. If leakage occurs due to poor sealing or parts are damaged due to insufficient strength, it will cause varying degrees of economic losses, such as conveying toxic, flammable, explosive or highly corrosive fluids, and may also lead to serious safety accidents. In order to ensure the sealing and strength of the valve, in addition to complying with the provisions of relevant standards, reasonable structural design and process quality, materials must also be selected correctly. Generally, valves for low-pressure non corrosive fluids use cast iron or cast copper; Cast steel or forged steel for high and medium pressure valves; Alloy steel is used for high temperature or high pressure valves; Valves for corrosive fluids are made of stainless steel, plastic, corrosion-resistant alloys (such as copper nickel molybdenum alloy, titanium alloy, lead alloy, etc.) or cast iron and cast steel lined with corrosion-resistant materials. Generally, the sealing surfaces of low-pressure valves are mostly, so our manufacturing enterprises should establish a sense of society and use brass or bronze. High and medium pressure valves mostly use stainless steel. High and medium pressure valves or high-temperature valves with high requirements use Cobalt Based cemented carbide. Polymer materials have been widely used in valves. For example, the valve seat of ball valve is mainly made of polytetrafluoroethylene plastic, and the sealing ring of butterfly valve and the diaphragm of diaphragm valve are made of various rubber materials. These materials have better sealing performance than metals in the temperature range that can be used. With the development of modern nuclear industry, petrochemical industry, including new energy materials, nano materials, advanced composite materials, eco-environmental materials, high-performance structural materials, new functional materials, new chemical materials and other electronic and aerospace industries, as well as the development of automatic process control and long-distance fluid transportation, the development of modern cryogenic valves, vacuum valves, valves for nuclear industry and various regulating valves has been promoted. The application of valve driving devices for remote control and program control is more and more

in the future, the development of valves will expand product parameters, develop energy-saving, labor-saving and self-control valves, improve structure, adopt new materials and processes, improve the service life of valves, and analyze and develop special valve series for the start-up of hydraulic system in testing machine factory, such as cryogenic valves, vacuum valves, valves for nuclear industry, safety valves, regulating valves for liquid oxygen, liquid hydrogen and liquefied natural gas Steam trap and valve driving device, etc

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