Strange Spheres in Journal Bearing Oil 1

[Metalguy]

We have recently found some tiny (5-12 micron) somewhat spherical objects in the journal-bearing oil of a large pump. They are primarily Fe, with some C and O. Previous oil samples have never found these. The oil is a simple R&O (rust and oxidation resistant) oil, and the bearings are tin-based babbitt. No Sn was found in the spheres via SEM/EDS.

Our lube engineer has read something about micro-melting of steel within fatigue cracks--something new to me.

Any ideas?

Gold is for the mistress - silver for the maid
Copper for the craftsman cunning in his trade.
"Good!" said the Baron, sitting in his hall
But iron - cold iron is the master of them all.
Rudyard Kipling

 

[CoryPad]

Any cast iron in the system? Spheroidal graphite/iron/iron oxide could come from it.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Metalguy]

Ah. Turns out this is a motor bearing, not a pump. Checking to see if cast iron, especially ductile iron, is present.

Lube engineer found these spheres using a 200X microscope--something he hadn't done before. I told him to go buy a 25X lens.<g>

Gold is for the mistress - silver for the maid
Copper for the craftsman cunning in his trade.
"Good!" said the Baron, sitting in his hall
But iron - cold iron is the master of them all.
Rudyard Kipling

 

[metengr]

Metalguy;
Is this a horizontal, split sleeve tin-based babbit bearing? The iron could be from the cast iron bearing housing or a seal that wiped bad enough to cause molten metal droplets. It could also be fine shot blast that somehow worked its way into the oil reservoir system. You should really have the bearing oil sent to an oil lab. This is what we do for our critical plant equipment to track metals and oil condition.

 

[btrueblood]

Is it possible that some component in the bearing housing is fabricated from powder-metal (sintered steel powder)?

 

[Metalguy]

This is a vertical shaft, 12,000 HP motor. The bearing housing is *probably* some sort of cast iron--still checking. Even though it's ~30+ years old, it could have had these tiny spheres in the oil since day one.

I'll see if the met. lab. we use can make a met. mount of one so I can see what the microstructure looks like. We picked the spheres up, along with a bunch of other stuff, with
Scotch tape to look at them in the SEM--don't know how well that'll work trying to make a mount.

Gold is for the mistress - silver for the maid
Copper for the craftsman cunning in his trade.
"Good!" said the Baron, sitting in his hall
But iron - cold iron is the master of them all.
Rudyard Kipling