itsmoked
Electrical
- Feb 18, 2005
- 19,114
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 -
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 -
