Hot bearing
Hot bearing
(OP)
Hi Guys,
We have installed a 250Kw 4pl motor on a pump application, the motor is running at 47hz and drawing 350 amps, the nameplate details are as follows: 250Kw 4pl 400-690 D/Y 50Hz Class F, B temp rise, IP55, VSD rated with 3 x PTC's. This motor is working in a large machine room with an ambient of 13 deg C at present outside temp at the moment between -5 to + 2. The bearing on the drive end is a cylindrical roller, the NDE is a insulated ball. The roller at the DE is measuring 78 deg at the bearing cap and the NDE bearing is 23 deg C, around the top of the fins behind the terminal box (roughly in the middle) the temp is 67 deg. The motor is cooled by its own fan, the vsd has not gone out on over temperature or over current and it is working away fine but we are concerned by the temp of this NDE bearing, i checked the grease plate and it is not over full, when we stopped it for a few hours the temp dropped and it gradually creeped back up to 78 deg over the coarse of a few hours as the motor warmed up. Any comments would be welcome.
We have installed a 250Kw 4pl motor on a pump application, the motor is running at 47hz and drawing 350 amps, the nameplate details are as follows: 250Kw 4pl 400-690 D/Y 50Hz Class F, B temp rise, IP55, VSD rated with 3 x PTC's. This motor is working in a large machine room with an ambient of 13 deg C at present outside temp at the moment between -5 to + 2. The bearing on the drive end is a cylindrical roller, the NDE is a insulated ball. The roller at the DE is measuring 78 deg at the bearing cap and the NDE bearing is 23 deg C, around the top of the fins behind the terminal box (roughly in the middle) the temp is 67 deg. The motor is cooled by its own fan, the vsd has not gone out on over temperature or over current and it is working away fine but we are concerned by the temp of this NDE bearing, i checked the grease plate and it is not over full, when we stopped it for a few hours the temp dropped and it gradually creeped back up to 78 deg over the coarse of a few hours as the motor warmed up. Any comments would be welcome.





RE: Hot bearing
RE: Hot bearing
If it really is a higher than normal temeprature as compared to historical or sister units, then some possible causes can include:
overgreasing (housing full)
recent greasing (temperature tends to spike up
other lubrication problems - incompatible or aged lubriants
excess load - from misalignment of direct coupled machine or from excess belt tension of belted machine.
skidding - use of cylindrical roller bearings in direct coupled application.
In addition to question above, if you provide the machine speed, bearing part number, and connection to driven load (belted or coupled), we can provide some more discusion. For example the SKF website lists minimum load for cylindrical roller bearings to prevent skidding at various speed. If you provide the requested info we have enough info to determine whether this is a misapplication of a cylindrical roller bearing.
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RE: Hot bearing
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Hot bearing
RE: Hot bearing
The attached spreadsheet is a calculation for NU319 bearing showing the minimum load is 2.5kN. I used the per SKF guidelines shown here
http://www
If you look here you will see a motor somewhat similar to yours... weight is 2650 pounds
http:/
If you look here, the rotor weight is typically somewhere around 1/3 of motor weight.
ht
So let's round up to 2700 pounds motor weight and take 1/3 to estimate your rotor weight as 900 pounds. Half of rotor weight per bearing would be 450 pounds. That is around 2 kN load per bearing. It falls short of the 2.5kN minimum load to prevent skidding specified in the SKF catalogue.
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RE: Hot bearing
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Eng-tips forums: The best place on the web for engineering discussions.
RE: Hot bearing
I learned something here.
Thanks.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Hot bearing