Claire Christian Valves April 14th, 2019 - 12:33:12
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.
Many people usually get motivated to get titanium valves because they want to increase the maximum revolutions per minute that they get. An engine that has titanium valves also tend to operate better in the long run, as it receives lesser stress. Though many drivers feel that these valves are quite pricey, many also think that they are a good investment. They are apparently good for the engine, as well as the total performance of the car. However, it is just as important to check the quality of the valves being sold in the market as not all of them are of the same quality.
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.
The last one is the valve type and sizing. Over-sizing of valves sometimes occurs when trying to optimize process performance through a reduction of process variability. Over-sizing the valve may hurt process variability in two ways. First, the oversized valve puts too much gain in the valve, leaving less flexibility in adjusting the controller. Best performance results when most loop gain comes from the controller. The second way oversized valves hurt process variability is that an oversized valve is likely to operate more frequently at lower valve openings where seal friction can be greater, particularly in rotary valves.
Among all the above mentioned considerations, it is rather necessary to talk about the actuator and positioner design. These two must be considered together. The combination of them affects the static performance (dead band), as well as the dynamic response of the control valve assembly and the overall air consumption of the valve instrumentation.
Needle Valves are used whenever control or metering of steam, air, gas, oil, water or other non-viscous liquids is required. This means they are used in almost every industry over a massive range of applications. Swagelok Valves are all factory tested with nitrogen at 1000 psig (69) bar to ensure that seats have a maximum allowable leak rate of 0.1 stdcm3/minute, and shell testing is performed to a requirement of no detectable leakage with a liquid leak detector.