An MDF press (medium density fiberboard)has run for about ten years without bearing failure. Within the last 2 years there have been four bearing failures. The post mortem of the bearing revealed corrosion as a possible root cause of the failure.

Formaldehyde gas is released during the pressing operation. Is it possible for the Formaldehyde to condense in the oil system and create Formic acid?

Many Thanks,
David McCall

David,

Formic acid requires water molecules to be available for each molecule of formaldehyde, and may not be as simple as bubbling formaldehyde through water. However, with oil, normally there isn't that much water. But, formaldehyde could still act as a Lewis acid, but I'm not sure that would be enough to corrode bearing steel when we are talking about a small amount wafting into an oil reservoir. The oil would tend to protect the bearing from such corrosion.

Better to test the oil to see what you have there. A physical properties analysis of the oil is in order. Look for changes in the makeup of the oil versus new oil.

Also, what has changed over the last 2 years? If the bearings used to last 10 years, something must have changed. Are seals leaking? When the bearing was replaced after 10 years, was the new bearing installed differently? Is alignment an issue, etc.

Also, what kind of analysis was performed to pinpoint corrosion as the root cause of failure? For example, in wear particle analyis, corrosive wear refers to submicron wear particles in abundance, which aren't always formed by a chemical corrosion of the metal surface. Don't rule out mechanical wear causes that can be interpreted as corrosive wear.

With the bearings only lasting an average of 6 months, if formaldehyde in the oil is to blame, you should be able to see a significant accumulation of the carbonyl peak in an FTIR analysis when compared to the new oil. Try taking a sample soon after an oil change, and a bit later and seeing if the carbonyl peak increases.

Hope this helps.

Rich Wurzbach

MRG Power Labs
www.mrgcorp.com
rwurzbach@mrgcorp.com
717-843-8884

Dear David,

My experience with OSB production has shown that formulation of lubricants suggested by the press manufacturer has changed in the past two years. Based on your post involving bearings and oil, I am at a bit of a loss as to which area of the press you are referring. Oiling of the roll rods and outfeed chains has been problematic as of late due to the chemical reaction between the released gases and the lubricants. This is made more evident by the increase in reaction at the upper lubrication points (heat rising). Given more specifics on your bearing lubrication, we may be able to give some insight as to others with similar problems.

Thank you Rich and Shaun for your reply,
I was not clear in my original post. The four bearings that failed are in different locations. It is a little different from the typical OSB machine. This particular machine has several large rolls that press the fiber against a single very large roll through a steel belt. The rolls are hot, so there is significant off-gassing during the press operation.

The seals of these bearing housings rollers are not very tight, since we found significant fiber build up in the housings. So it is certain that what ever is in the air around the roll is also in the bearing housing and oil system.


The bearing that was inspected after failure had spalls that were spaced roughly at roller spacing. A few rollers had significant chunks missing. Many rollers were intact with only particle dents. Dark discoloration was present in all but the freshest cracks.

My heart of my question is: Is there anything in the gases (formaldehyde, water vapor,etc)that could cause corrosion in the bearings?

One theory is that the machine ran for years without oil changes, which may have allowed the depletion of corrosion inhibitors.

No formal oil analysis has been done until now. I have asked for TAN, particle count, spectrometric and photomicrographs. I will also ask for the FTIR test with an emphasis on carbonyl.

Thank you again, You have been very helpful.
David McCall