Tilting Pad Bearing Performance Comparison of LEG vs Other Types

Kingsbury's equalized LEG thrust bearings are fitted with leveling plates to ensure optimum load distribution and trouble free operation, while taking advantage of other features such as offset pivots to achieve the best possible performance. Other key features make the LEG bearing superior to other directed lubrication bearings in use today:

• Oil feed tubes connecting the base rings to the shoes ensures that cool oil does not bypass the film.
• The LEG feature is an integral part of the shoes, delivering oil immediately to the film.
• Large oil flow passages eliminate the possibility of clogging that can occur in nozzles.
• No oil seal rings are required, lowering power loss and simplifying design and installation.
• The LEG does not require special, higher pressure lube systems to deliver oil to the film.

These optimal design features are standard on the LEG and contribute to the performance advantages. However, the bearing's technological advantages extend beyond performance improvements. Since cool oil flows directly into the oil wedge, there is a significant reduction in the flow that results in much lower power losses that allows the use of smaller lubrication oil systems, cutting capital costs.

LEG bearings are perfect for retrofit applications and can be used to economically increase bearing performance in existing installations. Retrofitting with LEG bearings is the perfect solution if field experience has proven a bearing installation to be marginal or if upgrades or changes in operating conditions have caused an increase in load. LEG bearings can be installed quickly, with a minor modification to the housing for a bottom drain. Merely replacing standard bearings with LEG retrofits will immediately result in lower oil flow rates, power losses and shoe babbitt temperatures. For new applications as well as for retrofits, LEG thrust and journal bearings provide the following benefits:

• Lower friction power loss for increased overall machine efficiency.
• Lower operating temperatures and increased load capacity.
• Lower oil flow requirements and/or smaller lubricating oil systems and lower capital costs.
• Ability to optimize for maximum load capacity or to minimize power loss.

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LEG Bearings Outperform Flooded and Other Directed Lube Types

Kingsbury's LEG bearing design has proven itself through exhaustive testing and years of trouble-free operation to represent the ultimate in directed lubrication technology. Yet the design concept is remarkably simple.

The bearing shoes and base ring are constructed so that cool undiluted inlet oil flows from the leading edge groove in the bearing shoe directly into the oil film. The cool oil in the oil film wedge insulates the babbitt face from the hot oil carryover that adheres to the rotating collar.

Because of these features, LEG thrust bearings can:

• Reduce operating temperatures at the 75/75 location by 8 to 28°C, depending on load and shaft speed.
• Provide a load capacity increase of 15 to 35%.
• Operate at oil flow rates as much as 60% lower, with an accompanying reduction in power losses of 45%.

Power loss is lower than both flooded and spray feed bearings due to the elimination of parasitic losses. The flow of cool oil over the leading edge lowers shoe surface temperatures, increasing the LEG bearing's capacity. The resulting performance improvements are shown in these graphs.