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Valve control.

Valve control.

Valve control.

I have to turn an 8" butterfly valve 90 degrees in 250ms.  I need about 150in-lbs to assure turning ability.

I need to do this electrically, not pneumatically.  I'm going in circles dithering over what method to use.

The valve needs to open that fast but can take a long time closing (seconds). It closes into the highest torque need as the butterfly seats into the gasket. Unseated it takes only about 15in-lbs to turn.  The 90 degrees isn't important at all.  It could be 80 degrees or 100 degrees, no matter.

I'm considering a gear motor which can dish out 150in-lbs at 60RPM which by definition gives 90 degrees/250ms.  Then possibly detecting the stall as it's closing. Or maybe using a microswitch to signal "closed" just as it's happening, to suspend drive.

But then I start thinking I could need a profile to close it reasonably.  That gets me thinking I need a servo motor to know right where everything is all the time.

Then I think nothing will change so why not use a stepper motor to just go to the dead reckoned closed location each time.  But then I start thinking about the noise you get with steppers, especially one that will result in 150in-lbs. I don't really want to hear whining every cycle.

Running a servo just 90 degrees seems like some kind of overkill/waste.  I wonder about some sort of bell-crank linear actuator instead - extend/retract.  But suspect this might be the most expensive method.

Can we get some discussion on this.   Suggestions?  Ideas?

Keith Cress
kcress - http://www.flaminsystems.com

RE: Valve control.

Electro-hydraulic actuator: opens under power, big spring and hydraulic dump valve for return. They're available as self-contained packages.

If we learn from our mistakes I'm getting a great education!

RE: Valve control.

Gaahhh.  Are we talking a hydraulic power pack having to run to supply the hydraulic pressure?  Hoses, leaks, and what not?

I think the 'spring closed' is a great idea though! That would keep the valve shut under no excitation and would completely take care of the otherwise tricky torque spike just around the valve seating position.

This would certainly reduce the control issue to just a sloppy 'open till a micro-switch is reached'.  Then I could just drop back to holding torque for the valve open duration of 2~5 seconds.  Then power off, for the spring to work its magic.
The only down side is the motor needs to now run the spring too.

Do you know of any spring thingys that are available for use with valve stems?  Is that an OTShelf item?

Thanks Scotty.  Thought I might've being posting into a blackhole.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Valve control.

No, there's a motor - a stepper in some designs - within the hydraulic pack to drive the hydraulic pump. No hoses. Just connect wires to it and off you go.

Check out the likes of Fisher (part of Emerson now) for ideas on valve actuator designs if you want to make your own.

Rotork have a hydraulic unit which will do what you want. Rotork don't know what 'cheap' means but they are a quality product and are designed to live outside for years between maintenance overhauls.

If we learn from our mistakes I'm getting a great education!

RE: Valve control.

You may use dc motor with gear and end switchs or an electromagnet with a mechanical arm amplifier to reach 90 degree.

RE: Valve control.

To rotate 90° in 250ms? Read the whole requirement.

If we learn from our mistakes I'm getting a great education!

RE: Valve control.

Maybe with electromagnet is too complicate but with DC motor seem to be much simple. 150in-lbs is about 16Nm and 60rpm is minim axe speed to reach 250ms. you can choose a 1.6Nm 600rpm DC or 0.32Nm 3000rpm DC motor with 1:10 or 1:50 gear ratio; sensing motor currrent can cut power to stop (like car windows). Stall motor current is much higher than nominal current and may be used for stop w/o using switchs. Any DC motor support stall current for 1-2 seconds.

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