Strange corrosion of Steel Journal

[BrianBT]

We have a failure of a swivel arrangement which sits in a load path of a derrick.

The fauilure takes the form of material loss from the journal surface (dia abt 150mm) leaving being a very uniform patten of hemispherical lumps which one assumes must have been related to some fabrication or previous repair process. the lumps are about 10mm in diameter.

I have attached a pitcure of one of the journals. The damage is repeated in a negtive complimentary way in the brass/bronze journal.

Can anybody shed any light

 

[metengr]

BrianBT:
Is there grease or other lubricant used in this bearing?

 

[Metalguy]

Weird. Electrical arcing? That should leave lots of discoloration though.

"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein

 

[Compositepro]

The pattern looks manufactured. Could it be there to hold in place a cast-on bearing material which has worn away?

 

[BrianBT]

Many thanks for your prompt replies

Yes it is supposed to be greased but there was evidence of this

The bearing in which it runs appears to be a brass/bronze and has dimples which match the humps.

We do not believe that there are no additional bits that have disappeared although there are no assembly drawings

It definitely appears as the non-deliberate result of some manufacturing process.

 

[Compositepro]

Maybe you bronze sleeve bearing seized and is supposed to be on the journal. Just a thought.

 

[boo1]

The dimples are uniform, appear to be fabricated. Possibly a lubrication feature of a bushing liner.

What is the bearing model?

 

[metengr]

As a suggestion and something I would do is use a high power magnifying glass under good lighting conditions and have a much closer look at these dimples along with a closer look of the journal surface material in between the dimples. See if you can evaluate if the dimple is caused by transfer of metal or raised.

I studied the photo and the more I look at this I can't come to grips with an explanation of how this surface texture was created - manufactured or caused by some effect in service.

 

[MikeHalloran]

The pattern looks like bubble wrap, replicated somehow.
But bubble wrap shouldn't be there in service, and I'm having a hard time figuring how it could corrode two surfaces if it were present.



Mike Halloran
Pembroke Pines, FL, USA

 

[unclesyd]

If this is stationary and subject vibration you could have a form of brinelling or some way type fretting. I would have to see the surface at a higher magnification to maybe pin it down.
Brinelling and fretting are the most likely way I know that will transfer patterns.
Another possibility is abrasive transfer if the shaft is stationary and vibrates.