There are many types of valves, but according to the characteristics of its action is divided into two categories, that is, the drive valve and automatic valve.
Driven valve is operated by hand or other power operated valve. Such as the cut-off valve, throttle valve (needle valve), gate valve, plug valves, etc., are these types of valves.
Automatic valve is the use of the medium itself flow, pressure or temperature parameters of the change and its own action of the valve. Such as check valve (check valve, Dan Liufa), safety valve, float valve, valve, valve and steam trap, etc., are automatic valve.
Engineering pipeline and the nominal pressure of the valve by GBJ235 - 82 standard is divided into: low pressure 010MPa. P≥ 9MPa;; working temperature ≥ 500. General water and warm engineering are low pressure systems, large power station boilers and various industrial pipelines with medium pressure, high pressure or high pressure system.
Here only the introduction of cold, hot water, steam and other common pipe valves, for other industrial pipelines due to the transmission medium is different, there are a variety of different requirements, according to the requirements of the valve.