KingCole Tilting Pad Thrust Bearing

Advantages of KingCole LEG Technology

Leading Edge Groove (LEG) technology, introduced by Kingsbury in 1984, advanced the performance of fluid-film bearings by enabling higher load capacity, lower friction losses, and controlled white metal temperatures. By directing cool oil into the hydrodynamic film at the leading edge of each pad, LEG lubrication improves thermal stability and operating efficiency.

The KingCole LEG bearing applies this proven directed lubrication approach in a non-equalized thrust bearing design. Compared to standard thrust bearings, KingCole LEG bearings deliver measurable improvements in temperature control, load capacity, and oil flow requirements.

When compared to a conventional thrust bearing, KingCole LEG 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 design of the KingCole bearing may resemble other non-equalized tilting-pad bearings, several key features distinguish it from competitive designs. These features allow KingCole LEG bearings to outperform flooded and spray-lubricated thrust bearings while maintaining a simpler, more compact configuration.

Pads

All KingCole bearing pads incorporate Leading Edge Groove lubrication to improve oil flow, reduce friction losses, and lower pad operating temperatures. Bearings are designed for a specific direction of shaft rotation, allowing pad pivots to be offset to increase load-carrying capacity. Because the design does not use leveling plates, pad heights are manufactured to tighter tolerances to promote improved load distribution.

Pad bodies are typically constructed from low-carbon steel with a high-tin white metal face. Alternative materials can be specified for unusual operating conditions or application requirements.

KingCole pads feature a raised spherical button on the back of each pad, allowing it to tilt freely in all directions. Unlike traditional rocking strips that permit motion in only one plane, this spherical pivot design improves self-alignment under load. Pad buttons are manufactured from carbon tool steel and heat treated to 52–57 Rockwell C to resist flattening. Kingsbury testing has shown this design significantly reduces temperature variation from pad to pad.

Carrier Rings

Carrier rings, typically manufactured by Coleherne, are produced to exacting ISO tolerances and are normally supplied split to simplify installation in confined or difficult-to-access locations. Standard construction is low-carbon steel with a minimum tensile strength of 483 MPa.

Lubrication ports in the carrier ring deliver oil directly to the bearing pads, ensuring even oil distribution and consistent pressure across the bearing surface.

Pad Retention

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

Oil Feed Tube

Oil feed tubes connect the carrier ring to each pad and are designed to allow unrestricted pad pivoting. This design directs oil precisely to the pad face while eliminating potential leakage paths and ensuring consistent oil delivery to the leading edge of the hydrodynamic film.

Bearing Housing Requirements

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

Fresh oil enters the bearing through an annulus located at the rear of the base ring. The discharge space should be sized to minimize interaction between discharged oil and the rotating thrust collar, and the oil outlet should be sufficiently large to allow free drainage from the bearing cavity.

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

Designed to Outperform Flooded and Spray-Fed Bearing Technology

Extensive testing and field experience have demonstrated that KingCole LEG bearings provide superior performance compared to flooded and spray-fed thrust bearing designs. While the underlying concept is straightforward, its impact on bearing performance is substantial.

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

In spray-fed bearings, lubricant is introduced between bearing surfaces rather than directly into the oil film. This can lead to uneven lubrication, the need for higher supply pressures, and an increased risk of small jet holes clogging with contaminants. The result is higher friction, elevated operating temperatures, and increased power loss.

By delivering oil directly to the leading edge and operating at reduced flow rates, KingCole LEG 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 reflected in the accompanying performance curves.

Applying KingCole LEG Technology

KingCole LEG bearings combine the efficiency benefits of Leading Edge Groove lubrication with a non-equalized thrust bearing design that offers simplicity, compactness, and ease of installation. This makes them well suited for applications where space constraints, operating stability, or system simplicity favor a non-equalized bearing solution.

Kingsbury’s engineering team can assist with bearing selection, performance evaluation, and retrofit considerations to determine whether KingCole LEG technology is the right fit for your application.

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