Actuator to control steam valve

Question

I have a steam radiator at home and it has a valve similar to the picture below.

Please note that the valve doesn't have grooves on top to attach things to.

I want to build something to turn it on and off depending on the temperature at certain points in the room.

I have that taken care of but cannot find a way to attach a actuator(actuator is the right word in the context I guess?) to turn the valve in both directions.

Also It is a rented apartment so I would like to avoid making any modifications to the radiator itself.

Answer 1

Well, being the manipulator removable, so you can attach other thing to the valve shaft, you have so much options.

Mechanical coupling

You could use a coupled rotary actuator to the shaft by the means of a shaft coupler. There's many types, this is a simple one, but you probably would not get the actuator axle full aligned with the valve shaft, so a coupler that permits some misalignment is desirable, like these:

rubber shaft coupler http://www.abssac.co.uk/uploads/products/cat_pp651_coupling%20jaw%202.jpg

Every coupler has its specifications and types of misalignment it will support.

You can use a belt or chain transmission too. Then you need to attach a pulley or sprocket to the valve axle.

Chain and sprocket transmission

Synchronous belt transmission

A possible problem with these two option is the lateral force the transmission could put on the valve shaft, as it has not made to support this, it probably will wear. ^{One way to overcome this is to use a shaft coupler to a bearing with the transmission, so the lateral force will be supported by the bearing.}

Electro-mechanical actuator

For actuating the valve, you can use a couple of options.

• A stepper motor.
• A DC brushed-motor with a reduction gearbox like this

^{The gears are show for illustration purposes, they are normally enclosed.}

There's many types of reduction gearbox too, I will not extend into this on this answer.

You probably need some way of knowing the position of the valve shaft (feedback). It can be a multi-turn potentiometer for simple analog output.

RC servo motor

If the valve needs less than 1 turn you can try to use an RC servo-motor, they have a DC-brushed motor, a reduction gearbox, a potentiometer for feedback, and a control circuit. You then feed with the angle position in a signal modulated by a technique know as PWM. Along the fact that the valve will operate at less than a 360° angle, you need to be sure the torque of the RC servo motor will be superior to the needed. Also metal gears and shaft will provide a more robust system, considering the torque.

Assembly

^{@DiegoCNascimento the image can be used with credits}

Here's a final assembly possibility. You should be sure the pipe could support the forces involved with a safety margin, if not, use the wall mount supports.

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Note: some valves main axles will go up or down when rotated, if this is the case the mechanical coupler should support this.

I do not assume any responsibility by any damage or injure in the mounting of this, the user should have plenty attention he/she is working with high-temperature and high-pressure parts that can pose danger.

Answer 2

If the valve has enough traction with a rubber band¹, you can use one to control the valve as in the image below.

To make sure the rubber band doesn't start falling over time due to gravity, you could attach a half-circular plate under the valve, so the rubber band wouldn't slowly slide down as it would rest on that plate. Note that the amount of the pressure on the plate should be very small, since the rubber band is quite stretched to provide enough stretch for rotation, so a not so strong glue might do the trick for that plate.

¹ This both depends on the material it's made of and quite importantly, how much torque is required to turn the valve.