Agitator motors

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steve66

Senior Member
Location
Illinois
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Engineer
Fortunately it is not my problem,

Four units. Two sharing the same conduit. All in PVC. Industrial control panel by others. Not my problem. Not my problem. Not my...:happysad:

My wife's favorite saying:

Not my circus,...not my monkeys!!

:)
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
That might work in a pinch, but it risks screwing up the fluid dynamics.
Not to mention taking on responsibility for performance of a mechanical device...

See above, "Not my (his) job..."

Years ago I used to tackle projects like that, but I have been burned too many times. I was just trying to help (usually so I could get paid), but when my "fix" didn't work, suddenly everyone FORGETS that it didn't work BEFORE I touched it and it becomes MY fault. No thank you...

Oh, and when it DID work? No extra cash...
 

topgone

Senior Member
That might work in a pinch, but it risks screwing up the fluid dynamics.

Yep. BTDTGTT thing!:)
If the designers thought an 11kW device does the stirring but the device installed is 19kW, I wouldn't be wrong if I trim the props so it just delivers 11kW!
Same amount of work? Or are there extraneous bits re stirring manure slurry that I missed there?
 

GoldDigger

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Location
Placerville, CA, USA
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Retired PV System Designer
Yep. BTDTGTT thing!:)
If the designers thought an 11kW device does the stirring but the device installed is 19kW, I wouldn't be wrong if I trim the props so it just delivers 11kW!
Same amount of work? Or are there extraneous bits re stirring manure slurry that I missed there?

It may seem that way on the surface, but the key performance element for the application is not how much power it draws but how much stirring it does.
By casually trimming the prop (giving it a bowl haircut) instead of changing the pitch you risk at best getting less stir per kW and at worst having problems with cavitation or other serious local conditions.

I am not saying anything bad will for sure happen, just that I am not the person to say that it won't!
 
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
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EC - retired
The idea of these pits and stirring machines is to keep the solids in suspension until it is run through a separator and compression cycle. Literally the stuff is squeezed out of it until the solids can be reused in the loafing area. The liquid is recycled to flush the barns again. Result is fertilizer, bedding and little to no additional water for the flush. More than I know.
 

Haji

Banned
Location
India
The power requirement of the agitator depends on the pattern of flow of the medium around the impeller. If it is a turbulent flow, its power requirement is low. To ensure it, the Reynolds number should be greater than 10,000.

Reynolds number=(impeller dia in ft squared)*(revolutions per hour)*(density of medium in pound per cubic ft)/(viscosity of medium in lb/hr-ft)
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
The power requirement of the agitator depends on the pattern of flow of the medium around the impeller. If it is a turbulent flow, its power requirement is low. To ensure it, the Reynolds number should be greater than 10,000.

Reynolds number=(impeller dia in ft squared)*(revolutions per hour)*(density of medium in pound per cubic ft)/(viscosity of medium in lb/hr-ft)

The typical threshold for turbulence is an Re of 2,300. Full turbulent flow is at 4,000. At least, so say Bird, Stewart, and Lightfoot.

BTW, your units don't cancel. You've got L3 left over. I think you may have the wrong units for viscosity.
 

GoldDigger

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Location
Placerville, CA, USA
Occupation
Retired PV System Designer
The typical threshold for turbulence is an Re of 2,300. Full turbulent flow is at 4,000. At least, so say Bird, Stewart, and Lightfoot.

BTW, your units don't cancel. You've got L3 left over. I think you may have the wrong units for viscosity.
I think that the appropriate units for viscosity are pound-seconds per foot squared.
 
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