Problems In The Selection Of Electric Actuators
Date:Oct 12, 2019
In general, the correct choice of electric actuators is based on the following:
Operating torque The operating torque is the most important parameter for selecting an electric actuator. The output torque of the electric device should be 1.2 to 1.5 times the maximum torque of the valve.
There are two types of mainframe structures for operating thrust electric actuators: one is to configure the thrust disc without directing the thrust disc; the other is to configure the thrust disc, and the output torque is converted into the output thrust through the stem nut in the thrust disc.
Number of output shaft rotations The number of rotations of the output shaft of the electric actuator is related to the nominal diameter of the valve, the pitch of the stem, and the number of threads. It should be calculated according to M=H/ZS (M is the total rotation circle that the electric device should meet). Number, H is the valve opening height, S is the stem drive thread pitch, and Z is the stem thread number).
Stem diameter versus multi-turn type open-end valve. If the maximum stem diameter allowed by the electric device cannot pass through the valve stem of the valve, it cannot be assembled into an electric valve. Therefore, the inner diameter of the hollow shaft of the electric device must be larger than the outer diameter of the stem of the open rod valve. For the partial rotary valve and the dark rod valve in the multi-turn valve, although the problem of the diameter of the stem is not considered, the diameter of the stem and the size of the keyway should be fully considered in the selection, so that the assembly can work normally.
If the opening and closing speed of the output speed valve is too fast, water hammer is likely to occur. Therefore, the appropriate opening and closing speed should be selected according to different conditions of use.
Electric actuators have special requirements that must be able to limit torque or axial forces. Usually electric actuators use a torque limiting coupling. When the specifications of the electric device are determined, the control torque is also determined. Generally running in a predetermined time, the motor will not be overloaded. However, if the following conditions occur, the overload may be caused: first, the power supply voltage is low, the required torque is not obtained, and the motor stops rotating; second, the torque limiting mechanism is erroneously set to be greater than the stopped torque. Cause continuous excessive torque generation, so that the motor stops rotating; Third, intermittent use, the generated heat accumulation exceeds the allowable temperature rise of the motor; Fourth, for some reason, the torque limiting mechanism circuit fails, causing the torque to pass Large; five is the use of ambient temperature is too high, relative to the motor thermal capacity decreased.