According to characteristics of chemical industry process of production, this paper details the pneumatic diaphragm valve, s choice on type, acting mode, specific property of flow and diameter size.

If press trip characteristics, the regulator can be divided into straight travel and quarter-turn;

Based the brake horsepower characteristics of low specific speed centrifugal pump and the required features of pumps used for agriculture, the concept of non - overload centrifugal pumps is conceived.