The Origin and Development of the Valve (2)
Sealing and strength performance are basic and the key performance for valves. Sealing of valves can be divided into internal sealing and external sealing. Internal sealing could be the sealing relating to the valve clack along with the valve seat external sealing could be the sealing involving the moving part of the valve stem as well as the valve bonnet, the valve body as well as the valve bonnet plus the valve body and also the connecting part of the pipeline. Valves are needed to not simply have good sealing performance, but also be safe when they are functioning.
If leakages happen on account of poor sealing performance or the part is broken on account of poor strength, different examples of economic losses will likely be caused. Transporting toxic, flammable, explosive or highly corrosive fluids can lead to serious accidents. To guarantee sealing performance and strength of valves, we should also correctly find the material besides reasonably designing the framework and ensuring of quality of the process based on the related standard requirements.
Usually, brass or bronze is adopted for the sealing top of the low-pressure valve stainless is used for high and medium pressure valves and cobalt based hard alloy is utilized for top pressure valves, medium pressure valves and also temperature valves that have high requirements. Polymeric materials have been popular for valves. As an example, PTFE is principally adopted for valve seats of ball valves, and various rubber materials is adopted for sealing rings of butterfly valves and diaphragms of diaphragm valves. This stuff have better sealing performance compared to those of metals at the applicable temperature range.
With the creation of the modern nuclear industry, the petrochemical industry, the electronics industry, the aerospace industry, automatic charge of process technology and long-distance fluid transportation, modern cryogenic valves, vacuum valves, valves for nuclear industries and various regulating valves are further developed. Increasingly more driving devices are put on handy remote control and program control.
The near future development trend in the valve is usually to expand parameters from the valve product, to enhance structures restore lives of valves, adopting new materials and new processes, and to develop valves with power saving, labor saving and automatic control and series of special valves like cryogenic valves and vacuum valves useful for liquid oxygen, liquid hydrogen and liquefied natural gas and nuclear industrial valves including safety valves, regulating valves, steam traps and valve drives.
Source: China Valves Manufacturer – Yaang Pipe Industry (www.ugsteelmill.com)