Selection of valves and design of pipes shall comply with the following principals:

　　In terms of locations and purposes of valves, the suitable valves can be selected after knowing relevant specification, size,

　　standards,principal and permission;

　　Need to specify the working condition, applicable medium, working pressure and working temperature of media;

　　Need to specify the nominal diameter to match the pipeline: DN（mm）

　　Need to specify the connecting type of the pipeline, including flanged type, inside&outside screwed type, welded type, wafer

　　type, clip type, groove

　　type,and union type etc.;

　　Need to specify the operating type of the valve, including lever, worm gear, pneumatic actuator, hydraulic actuator,

　　electromagnetic actuator and electromagnetic-hydraulic actuator etc.;

　　Need to specify the model of the valve, including gate valve, globe valve, throttle valve, ball valve, butterfly valve, diaphragm

　　valve, plug valve, check valve, safety valve, reducing valve, steam trap and plunger valve etc.;

　　Need to specify the working type of valve, including on-off type, adjusting type, safety type etc.;

　　Need to specify material of body and trim, including grey iron, ductile iron, carbon steel, alloy steel, stainless steel, monel alloy,copper alloy, aluminum alloy, plastic etc.;

　　Need to specify the requirements on

　　seal performance and grade or leakage;

　　Need to specify the requirements on coating, packing and transportation;

　　Need to specify face to face dimension, height, outline sizes, flow resistance, drainage ability, flow characteristic, protected

　　grade, anti-explosive performances etc. for special valves;

　　Need to specify the installed position and direction for the valve.