As the valve wide range of applications, the use of medium range of corrosion varies, so from national standards to industry standards make no provision for the life of the valve, Ministry of Machinery Industry in 1980 in order to improve the mechanical quality of industrial products and in line with national quality product appraisal, developed a "valve industry product quality grading regulations" in which the valve, closing Laval's first-class products, superior product provides life test requirements; such as Dn ≤ 200 ~ 400 high pressure valves grade scratch Views 2000 times, superior product is 4000 times. Because nuclear power plants are unique, the service life of valves for nuclear power countries have done a requirement; such as the U.S., France has 40 years, Japan was 30 years to 40 years.

Keywords:butterfly valve ,knife gate valve,ball valve,globe valve,slurry gate valve