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Flender DMGH 25.4 GEAR UNIT CARB BEARING FAILURE

Flender DMGH 25.4 GEAR UNIT CARB BEARING FAILURE

(OP)
Hello everyone ,
I am not so good in english but i will do my best to explain the situation .
My intership is in a ciment plant , I am working on a gear unit flender DMGH 25.4 .
the problem is on floating shaft Bearing , I am sure that the failure of the CARB bearing is due to the axial thrust of
helical gears. I m trying to find a solution to this problem , i found an other type of bears : cylidrical bears TYPE NU which support axial thrusr but it doesn't support a big load like the carb bearing do.
anyone has knowledge on this type of gear units , i will be glad if he give me some advices .
NOTE : CARB C 3164 M
I am going to upload the manifucturar document with this thread.

RE: Flender DMGH 25.4 GEAR UNIT CARB BEARING FAILURE

I haven't figured out which bearing you are talking about, i.e., the CARB bearing.

You are correct that helical gears produce a substantial axial thrust while transmitting torque.

The gearbox manufacturer surely knows that, too, and would provide thrust bearings appropriate to bear that axial load.

There are also good reasons for using helical gears instead of straight spur gears, which naturally introduce substantial noise and vibration as the full load is transferred abruptly from one tooth to the next. ... whereas helical gears can effectively have two teeth in mesh at all times so power is transferred continuously. Of course that's a simplified explanation, but it would be a good idea to read the Gear Handbook by Darle W. Dudley, or something similar at some point in your career, and also to review all the engineering data you can find on the various bearings in use.

If you can recover the failed CARB bearing, it might help to post photographs of it here.
It would be even better to also send it to the gearbox manufacturer for examination, _after_ getting in touch with them to report the failure and ask for their assistance. I am sure they have someone who knows a lot more about gears and bearings than I do or than you do. Perhaps we can both learn something from your adventures.


Mike Halloran
Pembroke Pines, FL, USA

RE: Flender DMGH 25.4 GEAR UNIT CARB BEARING FAILURE

CARB bearings are not designed to handle large axial loads. They are primarily intended for radial loads with some angular shaft misalignment. The bearing at the opposite end of the helical gear shaft should constrain the gear shaft axially in both directions. The CARB bearing should be installed so that it has a small amount of axial float. Otherwise, if it is over-constrained axially it can experience excessive loading

RE: Flender DMGH 25.4 GEAR UNIT CARB BEARING FAILURE

Okay, I had to look it up; 'CARB' refers to a self-aligning roller bearing. The day is a success because I learned something.

Figure 4 of the document you sent suggests that the helical gears driving the two girth gear drive pinions are of opposite hand, so there should be no net thrust on the 'Moveable shaft'.
Are you referring to a CARB bearing on that shaft having failed, or is there another one?

Have you taken advantage of FLENDER's offered telediagnostics?

Mike Halloran
Pembroke Pines, FL, USA

RE: Flender DMGH 25.4 GEAR UNIT CARB BEARING FAILURE

(OP)
Hello Mr Mike
Yes, what you said is true .
The pignon gears on the left and the right of the moveable shaft are designed to compensate the axial thrust ( V form .. or renault form )
I need to calculate thid axial and radial loads and see if there is an other type of bears which support this loads and work a little bit on lubrification

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