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Danny Harvey

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One client is having problems with overheating on their planetary reducers.

They routinely run them at 2250 rpm input instead of the 1790 that is normal.  My thought is that this is causing overheating, a drop in viscosity and premature gear wear.

Does anyone have experience with the speed limitations on this type of reducer?
John from PA

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Reply with quote  #2 
Quote:
Originally Posted by Danny Harvey
One client is having problems with overheating on their planetary reducers.

They routinely run them at 2250 rpm input instead of the 1790 that is normal.  My thought is that this is causing overheating, a drop in viscosity and premature gear wear.

Does anyone have experience with the speed limitations on this type of reducer?


You pose an interesting question so back at you.

Is it a planetary arrangement, or are you using the term planetary in a generic sense?

Is the machine fitted with an external lubrication system?

Is the client currently having failures, and if so describe. 
Danny Harvey

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I believe it is a true planetary reducer but I am not sure of the configuration.

No external lubrication system.

They are experiencing excessive heating and eventual lock-up.  No internal investigation occurs. Just remove and replace.

Walt Strong

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Is the gear reducer operating at a speed and/or load that is outside of the OEM design specifications? Is the lubricant type and level per OEM specifications? Do you monitor case temperature along with vibrations? I have found that ultrasound with contact sensor can indicate gear lubricant deterioration (viscosity reduction at near end of change interval).

Walt
ruben

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[CITA = Danny Harvey] Un cliente está teniendo problemas con el sobrecalentamiento en sus reductores planetarios.

Los ejecutan habitualmente a una entrada de 2250 rpm en lugar de la 1790 que es normal. Mi pensamiento es que esto está causando un sobrecalentamiento, una caída de la viscosidad y un desgaste prematuro del engranaje.

¿Alguien tiene experiencia con las limitaciones de velocidad en este tipo de reductor? [/ QUOTE]
ruben

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How much temeperature show the case?
What kind of oil use these equipments? (Manufacturer and type)

ruben

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[CITA = ruben] ¿Cuánta temperatura muestra el caso?
¿Qué tipo de aceite utilizan estos equipos? (Fabricante y tipo)


[/ CITA]
ruben

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Have you made oil analytics?
John from PA

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Danny, the speeds you cite would indicate that the machine is being operated at about 26% above normal so I think you are likely correct in your analysis of overheating and lubrication breakdown and resultant gear distress.  Not having an external cooling method just increases that possibility.  Foaming of the lubricant is also very likely.

Do you know the HP rating of the machine and its manufacturer?

You made the comment that there isn't any examination being done, "Just remove and replace" after failure.  Speculation on my part, but this makes me think that these machines might be relatively small, off the shelf catalog reducers.  Is product output related to speed?  The product must be worth more than a replacement gearbox?  These gearboxes might be purchased with a factory fill lubricant.  "Ruben" brings up a good point on the lubricant; assuming it is now a mineral based lubricant, if they could change to a synthetic it might improve the life considerably.  Synthetics work well in epicyclic gearboxes in that the foaming is substantially reduced.

As far as the arrangement I've attached a graphic of epicyclic arrangements.  If you know the ratio and the relative directions of rotation you can make a educated guess at the arrangement type, especially in a single stage machine.  The "solar" arrangement is somewhat rare and offers small ratios (1.2:1 to 1.7:1).  The "star" arrangement gives you some higher ratios (2:1 to 11:1) but flips the rotations.  Both the "solar and "star" arrangements have rotating ring (annulus) gears.  In the planetary arrangement the ring gear is fixed.

     

 
Attached Files
pdf Epicyclic Arrangements.pdf (152.42 KB, 19 views)

Danny Harvey

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I don't have any of the application details and I don't do the data collection or analysis.  I have repeatedly suggested that they monitor the temperature on the ring gear and perform routine oil analysis but they still don't.

These drive some conveyors and I suppose that they are oversped to increase production but don't know that for a fact.

I suggested that they change to a synthetic lubricant and add some external cooling. I was not keep on their idea to use compressed air because it might make for uneven heating/cooling of the ring gear and result in pitchline abnormalities.

As far as I know, these are as John describes:  small, off-the-shelf, right out of the catalog reducers.  The product is quite high in value and the contracts are now quite time sensitive due to retaliatory tariffs from their export destination country.

Thanks John, Walt and Reuben for the helpful suggestions.  If I can get them to just put a floor fan on them, we would likely be in better shape. Changing them to drives capable of handling the speed probably isn't going to happen. My guy on site will look at the nameplate, though and I will tell him to look at the sight-glasses for signs of foaming.

I'll let you know what I find out.
Walt Strong

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Reply with quote  #11 
Compressed air is the most expensive cooling method. A fan with better lubricant would probably be the way to go, as you suggest.

Walt
Danny Harvey

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Reply with quote  #12 
I had a running battle with one client about the use of compressed air to cool fan bearings.  First off, as Walt points out, it's really expensive. They had rigged up a 3/8" line to several big Cooper pillow block bearings that were running hot because they weren't properly installed. They wanted the air blowing on the bearing which made things worse because cooling it from the outside actually made the housing shrink before the bearing and made the clearance tighter. I told them if they must blow compressed air to cool things down, they were better off blowing it on the shaft so that the bearing would cool from the inside out and open up the clearances.  

After years of us moving the lines back and forth, they finally listened and assembled the bearings right and were able to remove the air lines.

If anyone has a calculator for compressed air costs, figure out what it cost them to run 8 3/8" diameter lines at 100 PSI for 4 years.

The other point is that it's a little more tricky than just aiming an airline.
MarkL

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Reply with quote  #13 
Had a new customer running compressed air lines to cool some snl housings on a fan issue was incorrect installation first three monthly surveys had proved fitment issues. I told them how bad using compressed air was economically and thankfully they reinstalled a new set correctly and no temperature issues. The condition monitoring contractors there previously had been ignoring the setup for over 2 years......I say no more on that!
OLi

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Reply with quote  #14 

I have had 2-3 cases where cooling was surprisingly good, one was a pulp pump and the first case we saw a composite part bearing fail and there were 3 beside each other so one was always carrying some load and the FFT looked like a mess since the balls were everywhere. Customer put a fan on it and it got better and was run 6+ months that they needed. When looking afterwards I would not have put a bet on that.
In the other cases it is a small fan where we can't put a larger bearing that it need but a electrical fan makes it work, the same on a gluten mill but no compressed air part from testing, just electrical fans for those we can't fix or until they can be fixed.

 


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