Gate valve with electric actuator: selecting a multi-turn actuator
Electrically actuated gate valves are used for remote control, frequent operation or large sizes that take too long to close by hand. A wrongly sized actuator either fails to seat the valve or breaks the stem. These are the factors to consider.
TAZ Engineering Team · · 7 min
Multi-turn actuation
A gate valve needs many stem turns to close, so it uses a multi-turn electric actuator that drives the stem nut, turning rotation into axial wedge travel. In GOST designations an electric actuator is shown by the digit 9, as in 30s941nzh.
Torque and thrust
Required torque comes from wedge thrust at maximum differential pressure plus friction in the packing and stem thread. The valve manufacturer states the required torque for each DN and PN. Size the actuator with margin, but keep its maximum output below the stem’s allowable torque.
Turns and stroke time
Stroke time equals stem turns divided by actuator output speed. On large valves closing too fast causes water hammer; closing too slowly disrupts the process. Agree the stroke time with the designer.
Mounting and switching
The mounting flange is standardised, for example to ISO 5210 sizes F10, F14, F16 and so on. Gate valves usually close on torque so the wedge seats firmly and open on position so the stem does not jam on the backseat. Setting limit and torque switches is a mandatory commissioning step.
Enclosure and controls
Specify supply voltage, enclosure rating, climate class, explosion protection if needed, control mode (local, remote, fieldbus) and manual override. TAZ supplies gate valves with actuators set up and tested as an assembly.
Checklist
- DN, PN and maximum differential pressure
- required torque
- number of turns
- stroke time
- ISO 5210 flange
- torque and position switching
- power supply
- enclosure and climate
- explosion protection
- control interface