Slimline Tilting Pad Thrust LEG Bearing

Advantages of LEG Slimline Technology

Kingsbury’s Leading Edge Groove (LEG) Slimline bearings apply proven directed lubrication technology in a low-profile, fully equalizing thrust bearing design. Originally introduced in 1984, LEG technology has enabled equipment manufacturers to increase bearing capacity while reducing friction losses and maintaining babbitt temperatures within acceptable limits. The Slimline configuration extends these benefits to applications where axial space is limited.

Compared to standard thrust bearings, the LEG Slimline bearing is engineered to deliver measurable performance improvements without increasing envelope size.

When compared to a conventional thrust bearing, LEG Slimline bearings can:

Reduce operating temperatures at the 75/75 location by approximately 8 to 27°C, depending on shaft speed
Increase load carrying capacity by 15 to 20%, based on temperature reduction
Operate at oil flow rates up to 60% lower, with a corresponding reduction in friction losses of approximately 40%

General Description

While the overall arrangement of the LEG Slimline bearing may appear familiar, several design features distinguish it from conventional tilt-pad thrust bearings. These features allow SlimLine bearings to outperform flooded and spray-lubricated designs while fitting into extremely shallow axial envelopes.

Pads

All LEG Slimline bearing pads incorporate Leading Edge Groove lubrication to deliver cool oil directly into the hydrodynamic film. Bearings are designed for a specific direction of rotation, allowing the use of offset pivots to increase load-carrying capacity and ensure predictable performance based on design conditions rather than averaged operation.

Pad bodies are typically manufactured from low-carbon steel with a high-tin babbitt face, though alternative materials can be specified for unusual operating conditions.

The low-profile equalizing Slimline design uses a raised spherical button on the back of each pad to allow full 360-degree pivoting. Unlike strip-style pivots that limit movement to one direction, this configuration allows self-alignment under load. Pad buttons are manufactured from carbon tool steel and heat treated to 52–57 Rockwell C to prevent flattening. Testing has shown this design promotes more uniform temperatures across all pads.

Leveling Plates

Slimline leveling plates are assembled within the carrier ring and distribute load evenly across all pads. Their low-profile design allows installation in extremely shallow envelopes, making Slimline bearings well suited for retrofit applications where equalizing bearings could not previously be used.

Carrier Rings

Carrier rings are manufactured to ISO tolerances and are typically supplied in split halves to simplify installation in confined or difficult-to-access locations. Standard construction is low-carbon steel.

Pad Retention

Pads are secured using retaining fasteners that can be easily removed to facilitate inspection, service, or replacement.

Lubrication

Lubrication passages drilled through the carrier ring deliver oil to each pad via individual oil feed tubes. These tubes are designed to allow the pad to pivot freely while ensuring oil is directed precisely to the leading edge of the pad face. This configuration promotes uniform lubrication and eliminates bypass or leakage paths.

Bearing Housing Requirements

The housing requirements for LEG Slimline bearings are similar to those of standard thrust bearings. Oil seals are not required, as inlet oil is confined to passages within the carrier ring assembly.

Fresh oil enters the bearing through an annulus located at the outside diameter of the carrier ring. The discharge space should be sufficiently sized to minimize interaction between expelled oil and the rotating thrust collar. The oil outlet should allow free drainage from the bearing cavity.

A tangential discharge opening is recommended, sized at approximately 80% of the thrust collar thickness. When possible, the discharge outlet should be located at the bottom of the bearing housing or tangential to collar rotation.

Designed to Outperform Flooded and Spray-Fed Bearing Technology

Extensive testing and years of field experience have demonstrated that the LEG Slimline bearing represents a highly effective directed lubrication solution. While the concept is straightforward, its impact on performance is significant.

Slimline bearing pads and the carrier ring are configured so that cool, undiluted inlet oil flows from the leading edge groove directly into the oil film. This cool oil insulates the babbitt surface from hot oil carried over by the rotating thrust collar, resulting in lower operating temperatures and improved film stability.

In contrast, spray-fed bearings introduce oil between bearing surfaces rather than directly into the oil film. This can lead to uneven lubrication, higher required supply pressures, and a tendency for small jet holes to clog with contaminants. The result is increased friction, higher temperatures, and greater power loss.

By delivering oil directly to the leading edge and operating at reduced flow rates, LEG Slimline bearings achieve lower friction power loss than both flooded and spray-fed designs. Lower pad surface temperatures increase load capacity and improve overall bearing efficiency. These performance improvements are demonstrated in the accompanying performance curves.

Evaluating LEG Slimline for Your Equipment

LEG Slimline bearings combine the proven benefits of Leading Edge Groove lubrication with a low-profile, fully equalizing design. This makes them a practical solution for new equipment designs as well as retrofits where space constraints, thermal limits, or rising loads challenge conventional thrust bearings.

Whether replacing a non-equalizing bearing or specifying a new machine, Kingsbury’s engineering team can help determine how LEG Slimline technology can improve performance within your available envelope.

Contact Kingsbury to discuss LEG Slimline bearing selection, retrofit options, or application support.