A valve is a device which controls the flow rate, pressure or the direction. The controlled fluid can be the liquid, gas, the mixture of gas and liquid or the mixture of solid and liquid. The valve usually is composed of body, 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 change the area of the flow passage. https://thegioivan.vn/
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 development of smelting process and hydraulic machinery, the plug valve made of brass and lead appeared in Europe. Besides, with the wide application of boiler, in 1681 the safe valve with lever and heavy bob came into the world. Before the invention of the Watt steam engine, the plug valve and check valve were the most important valves. The steam engine leaded the valve into a new field namely mechanical industry.
With the increase of the steam flow rate and pressure, the plug valve can not satisfy the number of steam admission and exhaustion at all. In order to solve the problem, people then invented the slide valve. In 1840, the check valve with threaded stem and the wedge gate valve with threaded stem become the great breakthrough in the valve field. The two valves did not only meet the requirement for pressure and temperature at that time but also initially satisfy the need for flow regulation. Later, because of the rapid development of power industry, oil industry, chemical industry and shipbuilding industry, all kinds of high or middle valves sprang up like mushrooms. What’s more, after the Second World War, owning to the invention of new materials such as polymeric material, stainless steel, lubricating material, the old plug valve and butterfly valve gain the new application and the ball valve and diaphragm valve develop quickly.
All in all, step by step the valve manufacturing becomes one of the important sectors in the mechanical industry. There are a lot of applications for the valve. It is closely connected with our daily life. For example, the tap used for running water pipe and the reducing valve used for liquefied petroleum gas stove are the valves. What’s more, it is the essential part for different mechanical equipments such as gas engine, steam engine, compressor, pump, vehicle, ship or aerocraft.