Selection Basis of Valve Electric Device
Valve electric device is an indispensable device to realize valve programmable control, automatic control and remote control. Its motion process can be controlled by stroke, torque or axial thrust. Because the working characteristics and utilization rate of the valve electric device depend on the type of valve, the working specifications of the device and the position of the valve on the pipeline or equipment, it is very important to select the valve electric device correctly to prevent the phenomenon of overload (working torque is higher than control torque).
Operating moment is the most important parameter to select the valve electric device. The output moment of the electric device should be 1.2-1.5 times of the maximum operating moment of the valve.
One is to output the torque directly without the thrust disc; the other is to configure the thrust disc, and the output torque is converted to the output thrust through the valve stem nut in the thrust disc.
The number of rotating circles of output shaft: The number of rotating circles of output shaft of valve electric device is related to the nominal diameter of valve, the pitch of valve stem and the number of thread heads. The calculation is based on M=H/ZS (in formula: M is the total number of rotating circles that electric device should satisfy; H is the opening height of valve, mm; S is the pitch of valve stem drive thread, mm; Z is the number of valve stem thread heads).
Stem diameter: For open-rod valves of multi-turn type, if the maximum stem diameter allowed by the electric device can not pass through the stem of the matched valve, it can not be assembled into an electric valve. Therefore, the inner diameter of the hollow output shaft of the electric device must be larger than the outer diameter of the stem of the open stem valve. For some rotary valves and CONCEALED-ROD valves in multi-rotary valves, although the passage of stem diameter is not considered, the diameter of stem and the size of key groove should also be fully considered when selecting and matching, so that the valve can work normally after assembly.
Output speed: valve opening and closing speed is fast, easy to produce water hammer phenomenon. Therefore, we should choose the appropriate opening and closing speed according to different conditions of use.
Installation and connection modes: installation modes of electric devices include vertical installation, horizontal installation and landing installation; connection modes are: thruster disc; valve stem passing through (open rod multi-rotary valve); dark rod multi-rotation; no thrust disc; valve stem not passing through; partial rotation.