How to select electric Actuator for gate valve?
Electric gate Valve The correct choice of electric actuator is a basis to follow, the following points can be referred to:
1. Operating torque: Operating torque is the most important parameter to select the gate valve electric device, the output torque of the electric actuator should be 1.2~1.5 times the maximum torque of the gate valve operation.
2. The main structure of the operation Thrust Gate valve electric device has two kinds: one is not to configure the thrust disk, direct output torque, the other is to configure the thrust disk, the output torque through the thrust disk of the stem nut converted to the output thrust.
3. Output shaft Rotation ring Number: The number of output shaft rotation ring of the electric device is related to the nominal diameter of the gate valve, the stem pitch, the number of threaded head, to be calculated according to M=h/zs (m for the electric device should meet the total number of rotating ring, H for the gate valve opening height, s for the stem drive thread pitch,Z is the number of STEM threaded heads).
4. Stem diameter to multi-rotary Ming rod gate Valve, if the electric device allowed to pass the maximum stem diameter can not pass through the valve rod with the gate valve, it can not be assembled into electric gate valve. Therefore, the inner diameter of the hollow output shaft of the electric device must be greater than the outer diameter of the stem gate valve. Although there is no need to consider the passing problem of the stem diameter of the dark rod gate valve in the partial rotary gate valve and the multi-rotary gate valve, 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.
5. Output speed: Gate valve opening and closing speed if too fast, easy to produce water hammer phenomenon. Therefore, according to the different conditions of use, the appropriate opening and closing speed should be selected.
6. The gate valve has its special requirements, that is, it must be able to limit the torque or axial force. Usually the gate valve electric device adopts the connecting shaft of limiting torque. When the specifications of the electric device are determined, the control torque is determined. Generally operating within a predetermined period of time, the motor will not overload.
However, if the following conditions can lead to Overload:
First, the power supply voltage is low, can not get the required torque, so that the motor stop turning,
second, is the wrong adjustment torque limiting mechanism, so that it is greater than the stop torque, resulting in continuous generation of large torque, so that the motor stop turning;
third, is intermittent use, resulting in heat savings Exceeding the allowable temperature appreciation of the motor;
four, is due to some reason torque limit mechanism circuit failure, so that the torque is too large;
five, is the use of environmental temperature is too high, relative to reduce the thermal capacity of the motor.
Six, the basic protection method of overload is:
1. To the motor continuous operation or point operation of the overload protection, the use of thermostats;
2. The protection of motor plugging and turning, the use of thermal relays;
3. For short-circuit accidents, the use of fuses or overcurrent relays.