Selection of electric actuators for electric butterfly valves


Published:

2023-01-16

Due to the combination of butterfly valves and electric devices, the correct selection of electric devices after determining the butterfly valve is an important factor related to whether it can meet engineering needs in practical use. When selecting an electric device, not only should the aforementioned working environment, electrical control, and general technical performance be considered, but also the comprehensive technical performance of the electric device should be comprehensively considered.

Due to the combination of butterfly valves and electric devices, the correct selection of electric devices after determining the butterfly valve is an important factor related to whether it can meet engineering needs in practical use. When selecting an electric device, not only should the aforementioned working environment, electrical control, and general technical performance be considered, but also the comprehensive technical performance of the electric device should be comprehensively considered.
1. Allowable value of valve stem diameter
When selecting an electric device for the lifting rod valve, attention should be paid to the allowable valve stem diameter value, which must be less than this value. In addition, for multi turn electric devices, the requirements for the height of the valve stem cover (related to the valve diameter) should also be raised during selection. Rotating stem valves may not be equipped with stem covers.
2. Connection between valve and electric device
The connection type and size of valves and electric devices should comply with national standards: GB/T1222-1989 Connection of multi turn valve drive devices, and GB/T12223-1989 Connection of partial turn valve drive devices.
3. Output torque and speed of electric devices
The output torque value is one of the important technical parameters of electric devices and also an important parameter that needs to be selected during use. It is not advisable to use an electric device with excessive or insufficient output torque when assembling electric valves. Because in general, electric device manufacturers need to test and adjust the output torque value before leaving the factory, which is relatively accurate. If an excessive output torque margin is selected, electric valves will have great potential danger. Once the control protection fails, it is easy to cause valve damage (valve stem bending, valve body rupture), which can easily lead to pipeline system accidents. So it is not advisable to choose an excessive output torque margin. If the valve cannot be opened in actual work, it is also considered an unreasonable choice.
Regarding the determination of the output speed of electric devices, when there is no strict requirement for the opening and closing time of the valve, a slower speed should be chosen as much as possible.
Due to the unnecessary fast speed, the motor power will be increased under the same torque requirements, which not only wastes energy and increases engineering costs, but also increases the volume of the electric device and causes various waste.
At present, domestic self-developed electric devices are equipped with a limited number of motor specifications (usually 2-3 specifications) for each frame number, and the speed ratio range of the gear pair and worm gear pair in the main transmission is limited. Therefore, the torque and speed divisions for each frame number are not many.
4. Maximum thrust allowable value of electric device
If the axial force of the valve is borne by the electric device (i.e. the valve stem nut is in the electric device), its thrust value is not allowed to exceed the allowable value of the electric device.
5. Maximum number of turns of the valve stem nut
When selecting a multi turn valve electric device, it is necessary to specify the maximum number of turns of the valve stem nut during valve operation. This can correctly select the gear speed ratio of the position indication mechanism in the electric device, so that the position indication has sufficient accuracy to meet the observation of the valve opening and closing degree during valve operation. Otherwise, it may cause illusion and affect normal operation.
At present, some rotary valve electric devices have mechanical limits to prevent the inability to determine the position of the valve disc. The corresponding relationship between the connecting screw holes and keyway positions between these valves and the electric device is strictly required.