Worm and Wheel Gearbox Premature Failure

Hi all,

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.

3 thoughts on “Worm and Wheel Gearbox Premature Failure

  1. QPS has developed a fiber optics vibration sensor that is wide band , I wonder if it is useful to be used as a online monitoring tool to warn against the on set of these micro-cracks and spall ?

  2. What lubrication is being used? The wipe on the worm wheel looks like the lubricant film is not holding up. You might need a worm specific lubricant.
    A lot of the evidence is gone since this is such a late stage failure.

    The inner race damage is much heavier on one side, check the worm screw shaft for straightness. Pictures of the screw would be nice.

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