The electric control valve is a combination of a regulating valve and an electric device, so how to correctly select the electric device after the valve is determined is an important factor related to whether the actual needs can meet the engineering needs. When selecting an electric device, not only the aforementioned working environment, electrical control and general technical performance should be considered, but also the comprehensive technical performance of the electric device should be fully considered.
1. Output torque and speed of electric device The output torque value is one of the important technical parameters of the electric device, and it is also an important parameter that needs to be selected during use. Excessive or insufficient output torque of the electric device selected when the group is equipped with the regulating valve is not preferable. Because of the general situation, the electric device manufacturer needs to test and adjust the output torque value when the product leaves the factory, which is relatively accurate. If the excessive output torque margin is selected, the dynamic regulating valve will have great potential danger. Once the control protection failure occurs, the valve will be easily damaged (the valve stem is bent and the valve body is broken). Caused a pipeline system accident. Therefore, it is not advisable to select the output torque margin too large. If you can't open the valve in actual work, it is unreasonable.
Regarding the determination of the output speed of the electric device, when the valve is not strictly required for its opening and closing time, the slower speed should be selected as much as possible.
Because of the unnecessarily fast speed, the motor power will be increased under the same torque requirement, which not only wastes energy, increases engineering cost, but also causes the electric device to increase in volume and cause various wastes.
At present, the electric devices developed and developed in China have a small number of motor specifications designed in each frame number (generally 2-3 specifications), and the speed ratio range of the gear pair and the worm gear pair in the main transmission is limited. Therefore, there is not much torque binning and speed binning for each frame number.
2. Maximum thrust allowable value of the electric device If the axial force of the valve is borne by the electric device (ie, the stem nut is in the electric device), the thrust value must not exceed the allowable value of the electric device.
3. The maximum number of revolutions of the stem nut When using the multi-turn valve electric device, the maximum number of revolutions of the stem nut during valve operation must be stated, so that the gear ratio of the position indicating mechanism in the electric device can be correctly selected to make the position The indication has sufficient accuracy to observe the degree of opening and closing of the valve during the working process of the valve, otherwise it may cause illusion and affect normal operation.
4, the allowable value of the stem diameter The lifting rod valve selection electric device should pay attention to the stem diameter value allowed to pass, the stem diameter must be less than this value. In addition, for multi-turn electric devices, the height of the stem cover should be raised when selecting (related to the valve pain path). Rotary rod valves are not equipped with a stem cover.
5, the connection between the valve and the electric device The connection type and size of the valve and the electric device should conform to the national standard: GB/T12222-1989 multi-turn valve drive device connection, GB/T12223-1989 part of the rotary valve drive device connection.
At present, some rotary valve electric devices have mechanical limit to prevent the position of the valve disc from being judged. The correspondence between the screw holes and the keyway position between the valve and the electric device is strict.