Bearing Journal Rebuild

[USMechE6]

Hello,

We have a shaft's journal damaged from a locked bearing and are looking at options to refurb it. I know there are some processes to deposit more material down and then turn to spec - can anyone provide some guidance/considerations for what to select? I know bending stresses, thermal growth and other conditions are important but wanted some thoughts on the general fundamentals of the processes themselves and if anyone's had success/failure with them. I only know that the shaft is carbon steel, nothing more specific on the type. 160 mm nominal diameter, 100 mm wide bearing. Feedback would be greatly appreciated.

 

[JJPellin]

More details would be helpful. Ball bearing or roller bearing? Radial bearing or thrust bearing? Speed? Load? What type of machine is this part of? Are you constrained by cost or repair time?

With so few details, I would default to HVOF tungsten carbide. It is expensive, but has worked very well for shaft repairs in a variety of applications?


Johnny Pellin

 

[USMechE6]

Hi,

Thanks for the response. The link to the bearing is here Link Load is approximately up to 30,000 lbs., just 60 rpm. Cannot provide machine detail but service is continuous load, not shock-loading. Temperature variations less than 40 deg. F.

 

[JJPellin]

Based on that, my recommendation stands.

Johnny Pellin

 

[Tmoose]

The shaft may be "bent" from the heat and mechanical distress.
Repair methods that don't monitor the runout on the rest of the shaft can cause BIG PROBLEMS.
In-place weld/grind repairs, even ones that create handsome accurate journals are especially vulnerable to missing the "big picture."

The API Recommended Practice RP 687 rotor repair is full of practical information about the processes and pitfalls of repairing shafts and rotors.
The advice on straightening is especially painful, but needs to be considered carefully.

 

[USMechE6]

Thanks.

I will say that this journal is part of a shaft on a precision machine, so you're especially right about the runout. Fortunately we have specs on the tolerances to go by. Do any of these treatments have sensitivity to the base material used or dissimilarity? I ask because again I'm not sure exactly what kind of steel we have. Maybe that resource has this information.

 

[JJPellin]

I have never seen HVOF Tungsten-Carbide disbond from carbon steel. We have used this on steam turbine rotors running in excess of 700 °F. Can this rotor be removed for grinding or does the repair have to be made in place without turning the shaft? Certainly, repairs where the shaft cannot be turned are much trickier.

Johnny Pellin

 

[USMechE6]

Good to know. The entire assy (welded together) can be removed from the machine and turned.