High Bearing Loading

Past Turbine Tips have covered the main reasons for bearings to wipe: 1) Insufficient lube oil supply, 2) Low lube oil pressure, and 3) Water in the lube oil. Every once in a while a fourth cause appears: High bearing loading.

Proper bearing loading is calculated by the elevations of the bearings, component weights and shaft alignments (bending moments, lateral, torsional). The OEM calculates the elevations and coupling alignments during the design process, based on the catenary curve (or sag chart). Calculations ofbearing loadings and alignment are usually accurate based on the design engineers’ mathematical calculations and computer model for the rotor’s geometry, speed, weight, and bearing design.

The Catenary Curve

Most of the time, high bearing loading is caused by misalignment of the turbine power train from the original design. That is, some force has moved the components from their original alignments. The source of the bearing failure can be eliminated by carefully measuring and re-aligning to the original specifications. But we have seen examples where the original calculations either were not accurate orover years of operation the bearing pedestals had moved.

Recalculating bearing loading is an arduous and potentially expensive process, so all other contributing factors should be eliminated before attempting this course. If necessary, TGM can perform the recalculation and re-alignment without the participation of the OEM. On three bearing units, it is not uncommon to utilize a dynamometer to check bearing loading during alignment and their adjustments.

An Attitude of Safety

Have you ever noticed that people who are successful in life, or are just happy, tend to have a positive attitude? And so it is with safety. Look at it this way–safety rules and procedures are written to protect you from harm. They are not written to make your work life more uncomfortable or inconvenient. After all, safety equipment and training costs your employer additional upfront money.

If you cooperate in safety matters, not only is there a lesser likelihood of you getting hurt, but you will not be doing battle with the people enforcing the safety rules. In addition, you should feel more confident on the job knowing you have a better chance of making it thorough the day without injury. Less fear of injury and the thought of no one on your back has to brighten your day!

We are not perfect. Even the best of us can forget or make errors in judgment. To maximize our safety efforts, we must look out for one another. If someone tells you that you are not working in a safe manner, do not become angry or defensive. They are just looking out for your well-being. If you did not know you were doing something wrong, be thankful your errors were noted before someone got hurt. If you simply forgot or got a little careless, be grateful that someone cares enough to get you back on track. If you see someone doing something unsafe, speak up, but do so diplomatically. Treat others just as you would like to be treated in the same situation.

Remember, attitude affects behavior. If you have a positive attitude, odds are you will exhibit safe behavior. A negative attitude toward safety will only cause conflict, stress and, ultimately, an accident.

This month, TGM celebrates over two calendar years without an OSHA-recordable accident. Please join us in our goal of an accident-free year.