Created Date: February 11,2010

Created by: Bob S BN

You don't mention a torque value to reliably turn the valve. You'll need this value to choose a motor.

Since you want it slow turning, a packaged gearmotor will probably get you the most compact package.

Have you looked in McMaster-Carr or Grainger at their gearmotor selections? They have many choices in both AC and DC. Some of the smaller Hurst motors in grainger are well built units. Here's a page with a bunch of them at Grainger...

http://www.grainger.com/Grainger/synchronous-motors-and-gearmotors/gearmotors/power-transmission/ecatalog/N-aqp?op=search

Depending on the torque to turn the actuator, this may be a good place to use a "rubber o-ring " drive. McMaster-Carr has pulleys and belts. If done right, this could give you give you your "overtravel " protection and your "manual turn " by allowing slip of the belt.

Just my $.02, Good Luck,

Created Date: February 11,2010

Created by: dieselvette

I like your belt-drive idea, thanks for the input. I would also consider using a rubber hose as a "shaft coupler " if the motor RPM was right. This one at Mcmaster-carr would work great, plenty of power: 6409K27

Required torque will be less than 0.25in/lb, unless the valve hits full-open or full-closed position. It could get stuck there and require much higher torque (depending on how hard it was turned) to get un-stuck. I hadn't thought of it at first, but this will also be a problem if I use a slip-drive of some sort. If it takes more torque to get it un-stuck than it did to bottom it out in the first place, that won't work.

I could just forget about the slip drive, and then include a current or position sensing device so that the PLC knows when to stop turning the valve. Maybe there's a stepper/servo with the right controller could do it. But I really want to avoid complicating it in that way, and adding expense.

Maybe I could attach a 10-turn pot to the needle valve shaft and stop the motor before it bottoms out hard. Or find a motorized pot that could turn it, but they 're rather spendy - and I want to stick with more common readily-available parts.

Created Date: February 11,2010

Created by: Bob S BN

Ya, you'll have issues if you hit the ends of the valve

I'll give you this site just to drool over, lots of clutches and motors and gears and stuff, but may get too complicated and spendy.

http://www.sdp-si.com/

If you can get over the manual part this might help. Do a direct, solid shaft coupling, and don't solid mount the motor so that it can rotate about the shaft. Use a couple compression springs next to an "anti-rotation " tab mounted to the motor. Springs will keep the motor from turning in normal movement. Install micro switches next to the "anti-rotation " tab so that at overload, the torque causes the motor to turn and hit a limit switch and stop the motor. Should fire right up in the other direction.

I know, a little complicated, but cheap.

Good luck, Bob

PS, I asked this b4 but never heard back. Do you have one, or did you build one?? A "dieselvette " I mean, or is that name from something else entirely?

Created Date: February 11,2010

Created by: dieselvette

(I'm posting this in "General apps " because I don't think a stepper/servo will apply)

We have an application where we need to monitor & control a corrosive gas pressure and/or flow under relatively low pressure (125 PSI max) and flow (up to 10 CFM). Responsiveness does not need to be quick, as the process variables will normally change very slowly.

I normally use a DL06 on the machine.

I would like to use a motorized needle valve for pressure control, so that with a pressure input it would act as a pressure regulator of sorts (we 're trying to regulate back-pressure so that we 're using as much flow as we can without draining the system of too much pressure). Sometimes it would also be used with a mass flow meter to control flow.

Mostly what I'm looking for is a suitable motor to control the 1/4 " needle valve that we presently use, the mechanics of it/mounting I can figure out. (I intend to arrange it so that in case of failure the needle valve can be controlled manually and so that if the valve is fully opened/closed and the motor keeps going, there is a slip fitting.) Needle valve is about 10-turns from open to close. I would like to stick with this valve because it is compatible with the gas, precise enough, and yet economical.

I don't think it would require a stepper. A simple reversible clock motor or other gear-reduction motor could work - Here's why: I intend to have it slowly close or open as needed to maintain SP. Don't even need to complicate it with a PID loop or variable speed motor. Can use buffers & hysteresis in the program to prevent constant "hunting " or "cycling ". (I have seen mass flow controllers that work in this way - they 're not quick to open or close but are able to maintain flow very precisely.)

Any suggestions for what to use as the actuator motor?