Worm and Wheel gearbox bearing failure

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Here is an interesting one. History is a worm wheel conveyor drive (Radicon Type). This operates in a rough environment and it ran for 8 months after maintenance and started to make a lot of audible noise.

It has a MJT 2 ¾ and a LJT 3 ½ on the input shaft. Coupling was the rubber pin type.

On inspection, there looks to be poor worm/wheel contact with some hair line surface cracks in the wheel gear. The gearbox input worm shaft NDE bearing has very bad damage.

We are thinking three possibilities for the root cause: Impact during mounting resulting in spalling at ball pitch and/or Spalls (Hertzian Fatigue) due to excessive thrust loading due to assembly or alignment errors. Also the possibility of transportation/storage damage. 

Anyone got any input?

Vibration Trends:

 

Acceleration trend showing increase after maintenance and the sharp increase.

 

 

PeakVue Trend showing a similar increase as the Acceleration trend.

 

 

Velocity Spectrum with high BPFI matches.

 

On Inspection Gear:

Incorrect gear meshing indications.

Visual surface hair line cracks.

 

Visual Inspection Outer Raceway:

Top left of image looks to be a hole in the raceway, there were two at 180 degrees opposite.

 

Microscope image of the outer raceway defect.

 

Visual Inspection of the Inner Raceway:

Images from around the inner raceway.

 

Microscope image of the inner raceway defects.

 

Visual Inspection of the Rolling Elements:

Two of the rolling elements, they all have various level of similar damage.

Microscope images of the rolling elements defects.

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