A valve is a device for controlling fluid flow, pressure and flow direction. The controlled fluid can be liquid, gas, gas-liquid mixture or solid liquid mixture. Valve is usually composed of valve body, valve cover, valve seat, headstock gear, drive mechanism, seal and fastener. The control function of valve is to realize the lifting, sliding, swing or rotary motion of the headstock parts by changing the size of the channel area by means of driving mechanism or fluid. The valve has a wide range of uses, and it has a close relationship with people's daily life, such as tap water taps, liquefied petroleum gas stove with pressure reducing valves are valves. Valves are also indispensable components for various mechanical equipment such as internal combustion engines, steam engines, compressors, pumps, pneumatic transmission devices, hydraulic transmission devices, vehicles, ships and aircraft. BC two thousand years ago, Chinese had used the water pipe valve bamboo and cork, and later use in irrigation channels gate, use check valves in the smelting of the bellows, the use of bamboo in the well salt mining and salt extraction plate check valves. With the development of smelting technology and hydraulic machinery, copper and lead plug valves appeared in europe. With the use of boiler, lever type safety valve appeared again in 1681. Before the advent of the Watt steam engine in 1769, plug valves and check valves have been the most important valves. The invention of steam engines brought valves into the field of mechanical industry. In Watt's steam engine, in addition to the use of plug valves, safety valves and check valves, butterfly valves are also used to regulate flow. With the increase of steam flow and pressure, the use of plug valves to control the steam and exhaust steam of the steam engine has been unable to meet the needs, so the slide valve appears. Around 1840, the valve with threaded stem and wedge valve with trapezoidal thread stem appeared successively, which was a major breakthrough in the development of valve. The appearance of these two types of valves not only satisfied the requirements of various industries for the continuous improvement of pressure and temperature at that time, but also met the requirements of flow regulation. Since then, with the development of power industry, petroleum industry, chemical industry and shipbuilding industry, a variety of high and medium pressure valves have been developed rapidly. After the Second World War, due to the development of polymer materials, lubricating materials, stainless steel and cobalt based cemented carbide, the old plug valves and butterfly valves have gained new applications, and the ball valves and diaphragm valves have been developing rapidly. The cut-off valve, gate valve and other valve varieties increased, quality improved. Valve manufacturing industry has gradually become an important sector of the machinery industry. Valve according to the use of function can be divided into cut-off valve, control valve, check valve, diverter valve, safety valve, multi-purpose valve six categories. The cut-off valve is mainly used for cut off fluid pathways, including cut-off valve, gate valve, plug valve, ball valve, butterfly valve, diaphragm valve pinch valve; the valve is mainly used for adjusting the pressure of the fluid flow, including control valve, throttle valve, pressure relief valve and the float valve; check to prevent reverse flow of fluid valve; valve for the distribution of fluid pathways whereabouts, or two-phase flow separation, including slide valve, multi valve, drain valve and air exhaust valve; safety valve is mainly used for security protection, prevent the boiler, pressure vessel or pipeline overpressure due to the damage; multi valve is a valve with more than one function such as the cut-off valve, drying both can play a role and can play the role of check. Industrial pipe valve according to nominal pressure can be divided into the vacuum valve, low pressure valve, pressure valve, high pressure valves, high pressure valve; the valve according to the working temperature can be divided into normal temperature, valve temperature valve, high temperature valves, cryogenic valves; valves can also be classified according to connection type, driving device and pipeline and the use of body materials etc.. Valves can be named individually or in combination according to various classification methods, or they can be named after the structural features or specific uses of the headstock parts. The basic parameters of the valve are working pressure, working temperature and caliber. For a large number of valves used in industrial piping, nominal pressure and nominal diameter are used as basic parameters. Nominal pressure refers to the maximum allowable operating pressure of a valve at a specified temperature.
A valve is a device for controlling fluid flow, pressure and flow direction. The controlled fluid can be liquid, gas, gas-liquid mixture or solid liquid mixture. Valve is usually composed of valve body, valve cover, valve seat, headstock gear, drive mechanism, seal and fastener. The control function of valve is to realize the lifting, sliding, swing or rotary motion of the headstock parts by changing the size of the channel area by means of driving mechanism or fluid. The valve has a wide range of uses, and it has a close relationship with people's daily life, such as tap water taps, liquefied petroleum gas stove with pressure reducing valves are valves. Valves are also indispensable components for various mechanical equipment such as internal combustion engines, steam engines, compressors, pumps, pneumatic transmission devices, hydraulic transmission devices, vehicles, ships and aircraft. BC two thousand years ago, Chinese had used the water pipe valve bamboo and cork, and later use in irrigation channels gate, use check valves in the smelting of the bellows, the use of bamboo in the well salt mining and salt extraction plate check valves. With the development of smelting technology and hydraulic machinery, copper and lead plug valves appeared in europe. With the use of boiler, lever type safety valve appeared again in 1681. Before the advent of the Watt steam engine in 1769, plug valves and check valves have been the most important valves. The invention of steam engines brought valves into the field of mechanical industry. In Watt's steam engine, in addition to the use of plug valves, safety valves and check valves, butterfly valves are also used to regulate flow. With the increase of steam flow and pressure, the use of plug valves to control the steam and exhaust steam of the steam engine has been unable to meet the needs, so the slide valve appears. Around 1840, the valve with threaded stem and wedge valve with trapezoidal thread stem appeared successively, which was a major breakthrough in the development of valve. The appearance of these two types of valves not only satisfied the requirements of various industries for the continuous improvement of pressure and temperature at that time, but also met the requirements of flow regulation. Since then, with the development of power industry, petroleum industry, chemical industry and shipbuilding industry, a variety of high and medium pressure valves have been developed rapidly. After the Second World War, due to the development of polymer materials, lubricating materials, stainless steel and cobalt based cemented carbide, the old plug valves and butterfly valves have gained new applications, and the ball valves and diaphragm valves have been developing rapidly. The cut-off valve, gate valve and other valve varieties increased, quality improved. Valve manufacturing industry has gradually become an important sector of the machinery industry. Valve according to the use of function can be divided into cut-off valve, control valve, check valve, diverter valve, safety valve, multi-purpose valve six categories. The cut-off valve is mainly used for cut off fluid pathways, including cut-off valve, gate valve, plug valve, ball valve, butterfly valve, diaphragm valve pinch valve; the valve is mainly used for adjusting the pressure of the fluid flow, including control valve, throttle valve, pressure relief valve and the float valve; check to prevent reverse flow of fluid valve; valve for the distribution of fluid pathways whereabouts, or two-phase flow separation, including slide valve, multi valve, drain valve and air exhaust valve; safety valve is mainly used for security protection, prevent the boiler, pressure vessel or pipeline overpressure due to the damage; multi valve is a valve with more than one function such as the cut-off valve, drying both can play a role and can play the role of check. Industrial pipe valve according to nominal pressure can be divided into the vacuum valve, low pressure valve, pressure valve, high pressure valves, high pressure valve; the valve according to the working temperature can be divided into normal temperature, valve temperature valve, high temperature valves, cryogenic valves; valves can also be classified according to connection type, driving device and pipeline and the use of body materials etc.. Valves can be named individually or in combination according to various classification methods, or they can be named after the structural features or specific uses of the headstock parts. The basic parameters of the valve are working pressure, working temperature and caliber. For a large number of valves used in industrial piping, nominal pressure and nominal diameter are used as basic parameters. Nominal pressure refers to the maximum allowable operating pressure of a valve at a specified temperature.
