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RustyCas

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Reply with quote  #1 
Do any of you guys work with large ball mills? 

If so, what type couplings do you usually see between the gearbox output shaft and the mill pinion gear shaft?  The pinion shaft is 8" diameter and turns 121 RPM.

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Noknroll

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Reply with quote  #2 
Mine have the Falk grid flex type coupling.
Beatnik

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Reply with quote  #3 
We use Kop-flex Max-C type WB. Never heard of any problems in 7 years. Our pignon shafts are 10.75" at 180 RPM

http://www.emersononlinecatalog.com/guide/Industrial_Products_Couplings/52.php  P.55
RustyCas

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Beatnik, I'm looking at that one as well.  I specified one of these (much smaller) to replace a clutch-type coupling on the input to a ball mill gearbox and it worked out very well.  Never had a problem with it and the rubber elements were easy to change.  But I assume the larger sizes would cost a lot more than a grid-flex.

The ball mill (that we used the Max-C on) had a large gear coupling on the output side and it mostly ran OK except for 2 instances.  The teeth on the hubs are "offset" to one side, and in one instance they mounted the hub backwards after a gearbox change-out.  When they started it up, I couldn't believe how smooth it all was.... until I noticed the mill wasn't turning!  The next instance, they actually followed my recommendation to clean an re-lubricate the coupling (1st time that's ever happened), but called me when they started it up because it was making a "terrible noise."  Took vibration data and surmised the coupling was "dry".  Lubricator said, no, he lubed it himself and he put "a lot" of grease in it.  So I had them open it up.  Well, the coupling had "a lot" of grease in it, but none on the teeth.  The grease fitting was not inline with the gear teeth, so it was all just piled up in the hub.  I tell people to ALWAYS pack bearings and couplings by hand, before they are closed up - but obviously they don't always listen.  (Effective training on basic maintenance practices seems not to exist, or not in Arkansas at least)

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John from PA

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Reply with quote  #5 
Quote:
Originally Posted by Beatnik
We use Kop-flex Max-C type WB. Never heard of any problems in 7 years. Our pignon shafts are 10.75" at 180 RPM

http://www.emersononlinecatalog.com/guide/Industrial_Products_Couplings/52.php  P.55


I've usually seen the grid type and a few times the Max-C WB that Beatnik refers to but I think that was on a synchronous motor driven coal crusher. 
Beatnik

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Reply with quote  #6 
On our new (and much bigger) mill we have torque limiters. As the name states, it acts as a coupling and a mecanical safety. 

It's a huge pain, when it opens it takes a lot of time and spare parts to re-boot the coupling and be able to produce again. The motor have everything it needs to protect itself (power and speed control), I've never heard any good arguments to justify the use of torque limiters outside "OEM say we need them and will void the garantee if we remove them".
Dan Timberlake

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Reply with quote  #7 
Ball tube mill Sold brand new in the last decade or so.
14 foot DIA 17 foot long for pulverizing coal

FALK xxxxT10 

Falk Steelflex Grid Couplings - no disk brake or controlled slip

Not that there aren't other ways to do it.

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RustyCas

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Reply with quote  #8 
Thanks, Dan.  They were "blowing up" the original coupling (likely due to gross misalignment -- before I was involved, of course) and went to a "custom" coupling, that weighs twice as much as the original and has to be aligned within a few thousandths. Not sure what they were thinking.  
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JB1

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Reply with quote  #9 
We replaced our mill gear coupling with http://www.atra-flex.com/ series "A" to eliminate the grease PM.
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