Gearing Failure
Gearing Failure
(OP)
Hello All,
My background is electrical engineering, so I apologize if I do not understand the proper terminology.
We have had a gearing failure and there is some dispute as to what has caused the failure. The gears are straight spur gears and reduce the speed from 1800 rpm to around 500 rpm in the gearing of interest. The final output speed is 56 rpm. The installed horsepower is 800.
Looking at the gears, they look like the teeth flowed outward from the contact area toward the outer edges of the gear. The gears were in service for approx. 3 months. Bearing damage was minimal.
There are two theories as to what happened:
1) The gears were too soft; or
2) They ran without oil.
I have the failed gearing, but hardness readings at this point would be futile. Any thoughts as to how to pursue this further.
Regards,
Raisinbran
My background is electrical engineering, so I apologize if I do not understand the proper terminology.
We have had a gearing failure and there is some dispute as to what has caused the failure. The gears are straight spur gears and reduce the speed from 1800 rpm to around 500 rpm in the gearing of interest. The final output speed is 56 rpm. The installed horsepower is 800.
Looking at the gears, they look like the teeth flowed outward from the contact area toward the outer edges of the gear. The gears were in service for approx. 3 months. Bearing damage was minimal.
There are two theories as to what happened:
1) The gears were too soft; or
2) They ran without oil.
I have the failed gearing, but hardness readings at this point would be futile. Any thoughts as to how to pursue this further.
Regards,
Raisinbran





RE: Gearing Failure
Either scenario is a possiblility, along with that of the gears being too narrow.
No breakage means strength is there, but presence of lube is critical. Until you have this under control, you will have little control or insight into failures.
RE: Gearing Failure
Regards
Dave
RE: Gearing Failure
Why not have the hardness measured and find out?
guess why you might not: it's a nitrided geartrain and only the teeth are hardened
If the gear is carburized all over, then the hardness should be measurable away from the damaged areas.
How about sectioning the gear and looking at the microstructure variation through the tooth cross-section? I would think that you'd be able to see case depth, etc.
Why not find and measure other gears from the same production run? Gears from current production?
RE: Gearing Failure
ZCP
www.phoenix-engineer.com
RE: Gearing Failure
zcp is correct-- have the gear(s) analyzed by a competent metallurgical/failure analysis company before you do anything else to them. There are a number of different items to address including the exact type of failure mode, case depth/hardness, surface microstructure, surface condition/roughness, etc. If you need a recommendation for a good lab in a specific area of the USA, I would be happy to provide one. Good luck.
RE: Gearing Failure
RE: Gearing Failure
http://www.tribology-abc.com/sub1.htm
Check out the various discussions on failure/reliability.
David Baird
Sr Controls Designer
EET degree.
Journeyman Electrician.
RE: Gearing Failure