Kingsbury Thrust bearing Pads damage!

[Mech5656]

Hello Engineers,

On one of the 9 stage Barrel pump (BB5 API style), which is pumping petroleum coke, we noticed that the Babbitt on pads (also called shoes) on thrust bearings are melted and moved to other pads. Please see attached pictures. Can you tell what has possibly caused this? Have you seen damage like this on Kingsbury thrust bearing pads? If yes, what was the issue?

 

[TugboatEng]

Why is it so corroded? Should it not have been in an oil bath?

 

[EdStainless]

Looks like it ran very hot.
Not enough lube, or poor lube circulation, of hot environment.
Babbit gets soft fast as it gets warm.

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P.E. Metallurgy, consulting work welcomed

 

[TugboatEng]

I agree that the bearing got hot and caused the babbitt to wipe off the surface. It even has the appearance of some heat tint or varnish in the blue circle.

Regardless, what is the up with all of the pitting corrosion (green circles)? Was this unit flooded with salt water at any time?

Kingsbury type bearings require lots of clean lubricating oil. Did the oil lack cleanliness or quantity or both?

How long did this unit sit in storage prior to commissioning?

 

[JJPellin]

For that style of pump, I would add a couple of other options. This could have failed from overload even if the lubrication was correct. Overload could be a result of a failed balance piston (balance disk, balance drum). Or, some pumps might have the balance line routed back to a suction drum with valves in the line. If the balance line was blocked in, the balance piston would not function and the thrust bearing could fail from overload.

In my refinery, I would use the term petroleum coke to describe a solid, not a liquid. You must be using the term differently than I would if your pump is pumping pet coke.

Johnny Pellin

 

[quadtracker]

I agree, most likely if it has a balance pipe it probably plugged off, which caused a heavy axial load on the thrust bearing from the extreme hydraulic pump forces in one direction. Some balance pipes have a restricting orifice or adjustable globe or needle valve to control flow rate. Petroleum coke can have solids in suspension which can build up over time in low flow cooler conditions. Majority of the thrust is controlled by the use of the balance pipe and the kingsbury thrust type bearings are to control the remainder of the thrust from the pump.

 

[electricpete]

It has the appearance of overload to me. Sounds like you got good advice. I think they covered environmental contaminants (based on rusty appearance), loading, correct lubricant.

One thing I'll add is speed (if the machine is variable speed). The bearings cannot sustain as much thrust load at lower speed. I don't know how the pump's thrust varies with speed and fluid conditions. If the speed is variable there may be more risk of someone making a mistake by operating the machine too slowly. Sorry if I'm stating the obvious.

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