Conveyor gearbox output shaft failure
Conveyor gearbox output shaft failure
(OP)
Could you help with the failure analysis of this shaft?
The shaft is the gearbox output shaft toward a low speed coupling. The gearbox is on a conveyor secondary drive assembly.
The shaft is the gearbox output shaft toward a low speed coupling. The gearbox is on a conveyor secondary drive assembly.





RE: Conveyor gearbox output shaft failure
Can you give us some information about the failure?
regards
desertfox
RE: Conveyor gearbox output shaft failure
RE: Conveyor gearbox output shaft failure
How long as the shaft been in service? and does it see a constant torque load or variable.
The failure to me looks like a fatigue failure and the river lines point toward the centre of the shaft, toward a little redish blue mark on the photo which suggests the area were the crack or cracks propagated from.
Thats about as much as I can say without more information such as material of shaft, loading, temperature etc.
I would further add that if the crack as I believe started from the centre of the shaft it would appear to be a material flaw that was there from day one perhaps from a incomplete heat treatment for example.
Regards
desertfox
RE: Conveyor gearbox output shaft failure
RE: Conveyor gearbox output shaft failure
Russell Giuliano
RE: Conveyor gearbox output shaft failure
The most practical advice I could offer as a practicing metallurgist, and not offending anyone, is to obtain the services of a competent metallurgical lab and have a failure analysis performed. I have been burned just relying on pictures to offer a root cause.
RE: Conveyor gearbox output shaft failure
metengr offered the best course of action, however, I am going to jump in and offer my opinion nontheless! There are at least four different fatigue crack origins on the outside diameter of that shaft, with two occurring in the locations that digger200 identified, and another two occurring at the 6 o'clock and 9 o'clock. There may be one at the 5 o'clock position too. The shaft definitely failed by overload after the fatigue cracks grew to ~ 60% of the diameter of the shaft. It is difficult to tell whether or not bending or torsion is the most significant contributor to the initiation and growth of these cracks. You definitely need to have a thorough metallurgical analysis performed of the fractured shaft.
RE: Conveyor gearbox output shaft failure
So Cagou, was there a stress riser?
Failure is a prerequisite of successful design
RE: Conveyor gearbox output shaft failure
Regards,
Cory
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RE: Conveyor gearbox output shaft failure
The conveyor has been in service intermittently to unload shipments. In total I would say it has been running under load 2 weeks in total.
RE: Conveyor gearbox output shaft failure
Some other checks I would be doing are things like the braking system,I am assuming that you have dual hydraulic pressures and also dual times for decelleration and full braking force?
And cuurent applied to the electric motor for drive(I seriously doubt you have a problem here but hey whilst maintenance are "doing nothing")
RE: Conveyor gearbox output shaft failure
I have to check the load applied on the shaft if the gearbox assembly was resting on it.
RE: Conveyor gearbox output shaft failure
Given the large size of the shaft, and the probable expense, you really need to take it to some grownups to look at.
Cheers
Greg Locock
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RE: Conveyor gearbox output shaft failure
Johnny Pellin
RE: Conveyor gearbox output shaft failure
You mentioned LS coupling, is it a parallel or taper fit shaft (from the photo, I assumed it was a hollow mounted reducer). If your LS coupling has excessive run out and your torque arm is rigid, your drive (via output shaft) will see full LS torque of the reducer - which it probably wont be designed for. The failure does not appear to have necking at the radii as I would have expected associated with this method of overload (though I am not a materials expert).
Being a secondary drive, the 2:1 drive ration means if the primary drive "sheds" 10 % of its share of the total load, the secondary drive see "20%" (not just when running, what about when starting). As you have VSD’s would probably have reasonable control.
There are plenty of other issues.
Regards,
Lyle
RE: Conveyor gearbox output shaft failure
RE: Conveyor gearbox output shaft failure
I work at EMO bulkterminal in Rotterdam and we have had a few broken drive shafts in the same looking matter as yours.
The cause was not one thing but a combination of some things.
We changed from mechanical drum brakes to hydraulic disc brakes. In case of emergency stops the brakingforce of the discs is higher than the drumbrake was. Another thing were our couplings. We drive with Voith turbo couplings (hydraulic) and when starting under full load these couplings sometimes blow their safety plug and lose their oil. When filled again, the filling was sometimes too much.
The coupling became too stiff and caused too much torque.
The fixation of the reaction arm of the driveset in some cases was not flexible enough, it allowed too less movement of the gearbox and the drumshaft
Like Lylebrown00 and Greglocock say: Have someone who knows his business make a full investigation an report
Succes,
Polleke