A valve is a device which controls the flow rate, stress or the direction. The controlled fluid can be the liquid, gas, the mixture of gas and liquid or the mixture of strong and liquid. The valve commonly is composed of physique, seat, bonnet, parts for opening or closing, actuating device, sealing element and so on. The controlling function of the valve depends on the actuating device or the movement of the fluid which drives the sliding, rotating or turning of the parts for opening or closing to alter the location of the flow passage.

Two thousands years ago, the Chinese people applied the bamboo trunk and wooden plug into water pipeline. Then later they applied the sluice into the irrigational canal, the plate check valve into bellows for smelting and so on. With the improvement of smelting approach and hydraulic machinery, the plug valve created of brass and lead appeared in Europe. In addition to, with the wide application of boiler, in 1681 the secure valve with lever and heavy bob came into the world. Ahead of the invention of the Watt steam engine, the plug valve and check valve had been the most significant valves. The steam engine leaded the valve into a new field namely mechanical industry.

With the improve of the steam flow price and stress, the plug valve can not satisfy the quantity of steam admission and exhaustion at all. In order to resolve the issue, people then invented the slide valve. In 1840, the verify valve with threaded stem and the wedge gate valve with threaded stem turn out to be the fantastic breakthrough in the valve field. Click Here did not only meet the requirement for pressure and temperature at that time but also initially satisfy the require for flow regulation. Later, mainly because of the rapid improvement of energy business, oil sector, chemical market and shipbuilding market, all sorts of high or middle valves sprang up like mushrooms. What is much more, after the Second Globe War, owning to the invention of new components such as polymeric material, stainless steel, lubricating material, the old plug valve and butterfly valve get the new application and the ball valve and diaphragm valve create rapidly.

All in all, step by step the valve manufacturing becomes a single of the vital sectors in the mechanical market. There are a lot of applications for the valve. It is closely connected with our every day life. For example, the tap utilised for operating water pipe and the lowering valve utilized for liquefied petroleum gas stove are the valves. What is more, it is the important element for different mechanical equipments such as gas engine, steam engine, compressor, pump, vehicle, ship or aerocraft.