Common Valves for Large Desalination Projects

Currently, a large amount of large desalination projects are being built in China. Valves are used as key devices for desalination project.

 

Chloride may corrode equipments during desalination. Temperature of sea water has great influence on velocity of corrosion. The higher temperature is, the faster corrosion is. Otherwise, solid contaminants can also damage protective film of materials, resulting in erosion corrosion. Other chemical contaminants also increase corrosion probability. Ingredient additives are a kind of artificial marine chemical pollutants. However, utilizing appropriate ingredient additives cannot cause pollution. For example, sodium hypochlorite can be used to suppress algaes while high dose can cause serious pitting corrosion. 

 

Utilizing rational valves can descend consumption of materials, local resistance and energy consumption, convenient for installation and maintenance.

 

Pipe diameter of desalination project is DN300-1600, having exceeded usable range of ball valve and globe valve. Compared with gate valve having same diameter, butterfly valve has the advantages of simple structure, excellent corrosion resistance, short length, low consumption of steel, similar coefficient of local resistance. For that, butterfly valve is more economical and practical when it is used as stop valve. Based on pressure, butterfly valve can be classified into low pressure butterfly valve and high pressure butterfly valve. 

 

Check valve is usually installed at the exit of pump, in case of back flow of sea water and damage to equipments caused by water hammer. At present, common check valves utilized for large desalination projects include slowly closing butterfly check valve, liner butterfly wafer check valve, single disc wafer check valve and single disc duplex steel wafer check valve.