Hi All,
I have been taking readings on a pair of pulpers for about 6 months now. I realize that seeing gmf is normal, and that any problems will most likely be indicated by high sidebands. I dont realy have a way of noteing the load on the unit because product is dumped in seemingly at random increasing and decreasing resistance for the pulper. When do i know that i should be inspecting the gears etc? Unit is on circulating/cooling lube system. Is there a certain % of gearmesh amplitude that a sideband should reach to warrent an inspection? Any input, specific or general would be greatly appreciated. I have included a spectrum. There is alot of energy present. I have zoomed in a little to make for better viewing.
Thanks in Advance!

This message has been edited. Last edited by: John Elliot,

John,

I think we need some more info before we can respond.

1. How many stages are in the gear box?
2. Does this box load/unload while you are collecting data?
3. Are you taching the speed or does it stay very consistent?
4. The sidebands are running speed of which shaft?
5. What type of gears are used?

More Questions:
Stud, flat magnet or 2 pole magnet? May be some resonance excitation.

Do you have an acceleration time waveform? Might be better for determining the nature and severity of any defects.

John,

The spectrum above appears to be one of an unloaded gearbox, or else you have severe wear.
The 3X gear mesh would lead me to believe backlash, and the excess broadband around it kinda makes me believe that is the case also.
I like to take a TWF on gearboxes.

The low 1X gm is not uncommon, but I see higher amplitudes than that on loaded gears.

I don't really have any hard and fast rules as to amplitude of sidebands, but rather I view it as I would a bearing, the numbers of sidebands are more of a gauge of severity than the amplitude of any particular one. It is not uncommon to see at least two sets around each gm peak, with the first set being around 1/2 the amplitude of gm peak on a heavily loaded gear set.

If that box is on a circulating system that is spraying lubricant down into the mesh, I would be surprised if doesn't last at least your lifetime. That is a good system of lubrication, and providing the gears are good to start with, will last a long time. I am thinking of Horsburgh-Scott type box with helical gears and spray lubricant.

Dave

1. goes from 1200ish to 400ish I have never seen the inside of this unit. One shaft in, one shaft out at 90 degrees up into the vessel.
2. Product is being dumped into vessel when i am collecting data
3. Constant 1200 since i started readings
4. The motor
5. I have never seen the inside of this unit.

2 Bar magnet, Not optimal at all but all i have right now.
I do collect a time waveform.

The following spectrum is two months befor first posted.

All good tips from others.

Do you have any similar spectrums from say three months back for comparison? Looking for a situation that is getting worse or staying pretty much the same.

It is evident that this is a bevel (out at 90 degrees up) so the fundamental quality of the gearing might not be all that high to begin with. If it has ever been apart and not reassembled by knowledgeable people then the bevel settings can be way off as well. Setting bevels is a highly specialized skill.

Very often bevels have a tooth combination that is susceptible to assembly phase issues as well. Check your tooth combination.

John from PA

This is a twf of the same point most recent

let me know what area you would like zoomed

Quick, you must have posted the older plot while I was typing, which I do by the hunt and peck method.

Clearly evident is a big change in the 2X of mesh, but a steady level of the 3X of mesh. Changes in 2X of mesh are often signs of tooth flank wear. Are you doing a lube oil analysis program?

You probably should schedule a peak into this thing when you get a chance. Usually there is an inspection cover and you should try to get a good look at the drive flanks of the gearing.

John from PA

John,please post your results on this problem.
We have had the same problem on a pupler at Armstrong plant, Marietta PA