Sign up Calendar Latest Topics Donate
 
 
 


Reply
  Author   Comment  
JuddJones

Sr. Member
Registered:
Posts: 384
Reply with quote  #1 
I would love to hear others thoughts on this outer race. I am guessing the discoloration near the holes in the race is related to corrosion? The pitting at the rolling element spacing under the microscope appears to be corrosion related, so is the discoloration at the holes in the outer race corrosion as well from the accumulation of oil leaving the bearing as its rotating?

  2017-09-20 15_17_46-Quad bearing resized 2.png 

Noknroll

Avatar / Picture

Sr. Member / Supporter
Registered:
Posts: 843
Reply with quote  #2 
Looks heat related to me, was the bearing removed cold? or heat applied?
Dark patch on the right looks like soot from an oxy-acetylene torch not adjusted properly from an orange carbonising? flame to an oxidising? blue flame. terminology maybe wrong but the colours are right. anyway, somewhere to start the discussion.
JuddJones

Sr. Member
Registered:
Posts: 384
Reply with quote  #3 
The spot on the right is another hole in the race in poor lighting. It looks just like the one at the bottom. The outer race was split with a cutoff wheel on a grinder. There is little to no H.A.Z. around the cut area. The color around the holes looked like heat to me as well, but not seeing any indication of heat from friction or rotation in the bearing. I thought maybe the lubrication got contaminated and oxidized the race where the oil was draining through while turning. The pitting at the roller spacing looks like corrosion under the microscope (pic below), so I know there was corrosion in play at some level, however the color around the holes has me slightly confused.
23236 outer race.jpg 

Ralph Stewart

Avatar / Picture

Sr. Member
Registered:
Posts: 235
Reply with quote  #4 
What does the backside of the hole look like?

Also, are all holes in this condition or only the ones on the loaded (bottom) side?

Had it been shutdown for an extended time and could any water in the oil system have settled in the bottom of the housing, if the other holes (unloaded/ upper oil holes) are not in the same condition?

Is this bearing from a paper machine dryer?

__________________
Ralph Stewart
AlertAnalytical.com
dmcmmc

Avatar / Picture

Member
Registered:
Posts: 69
Reply with quote  #5 
Is this a grease or oil lubed bearing?
JuddJones

Sr. Member
Registered:
Posts: 384
Reply with quote  #6 
Quote:
Originally Posted by Ralph Stewart
What does the backside of the hole look like?

Also, are all holes in this condition or only the ones on the loaded (bottom) side?

Had it been shutdown for an extended time and could any water in the oil system have settled in the bottom of the housing, if the other holes (unloaded/ upper oil holes) are not in the same condition?

Is this bearing from a paper machine dryer?

This bearing is from a bandsaw. All the holes are in this condition. Water in the oil is not real likely, it is inside with no water in use nearby. The saw is shutdown for 2 days a week, and has operated on this bearing for probably at least 8 years. Pic below of the outside of the bearing. The bearing is oil lubricated dmcmmc.

2017-09-21 06_54_17-IMG_3105.jpg


Ralph Stewart

Avatar / Picture

Sr. Member
Registered:
Posts: 235
Reply with quote  #7 
Thanks Big J.

It sort of looks like heat, as mention before.




__________________
Ralph Stewart
AlertAnalytical.com
John from PA

Sr. Member
Registered:
Posts: 963
Reply with quote  #8 
OK, we have a bearing which has lasted for 8 years and has prominent heat related discoloration, both inner and outer race surfaces, at the lubrication supply holes.  OP further states all the holes are in this condition.

I'd like to suggest that the discoloration has been present since the day the bearing was mounted and further suggest it was mounted with a torch.  When exposed to high heat, the areas around the holes would be most susceptible to the discoloration.

There may have also been some corrosive activity.  Even though a machine is indoors only a proper test of the lubricant can rule out water in the oil.  Any machine that is shut down cools off, and as it cools off cooler air enters through typically a breather.  Condensation on internal surfaces can occur.  Do you regularly do oil analysis on the lubricant?
JuddJones

Sr. Member
Registered:
Posts: 384
Reply with quote  #9 
Thank you John, that seems very likely. I am pretty sure a bearing heater would have been used, but it certainly could have been overheated when it was installed.
electricpete

Sr. Member
Registered:
Posts: 651
Reply with quote  #10 

Looking at the outside of the outer race, there are concentric circle/oval patterns which cross smoothly from the seating surface to the oil groove and onto the seating surface on the other side of the oil groove.  That is quite an interesting pattern in itself. Does anyone have an idea what would cause that?

JuddJones

Sr. Member
Registered:
Posts: 384
Reply with quote  #11 
I am still a little baffled by the color around the holes. I am almost positive a bearing heater would have been used to install this bearing. The inner race would have been really hot to get the outer race warm enough to turn it blue. For some reason I keep going back to oxidation in my little pea brain.
Noknroll

Avatar / Picture

Sr. Member / Supporter
Registered:
Posts: 843
Reply with quote  #12 
My money is on heat and then oxidation followed in the H.A.Z. if any moisture was present in oil
Might be difficult or even impossible to find out the heating method used to install 8 years ago
Pete, if the installer decided to localise heat with a gas torch around the lube holes would explain the concentric circle crossing from one surface to the other (inner to outer)
John from PA

Sr. Member
Registered:
Posts: 963
Reply with quote  #13 
Is there any chance those holes are drilled and tapped?  Such an operation is not that unusual and is done so that an oil control orifice can be added.

The range of colors supports that the local temperatures may have reached 400° to 500° F.  To do a drilling and tapping operation a tempering operation would have likely been necessary.

See attached chart courtesy of "By Zaereth - Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=18561876".

Tempering colors.JPG 

Previous Topic | Next Topic
Print
Reply

Quick Navigation:

Easily create a Forum Website with Website Toolbox.