Details
Kingsbury's patented Leading Edge Groove (LEG) thrust bearings can significantly improve a machine's performance, reliability, and efficiency.
Our LEG bearing design has been refined through exhaustive testing and represents the ultimate in directed lubrication technology. Yet the design is simple.The bearings are constructed so that cool inlet oil flows directly over the leading edge of the bearing shoe into the oil film which insulates the babbitt face from hot oil carryover.
Applications have proven that advanced design LEG bearings can, compared to already reliable standard Kingsbury bearings:
- Reliably operate with lower oil flow requirements.
- Substantially reduce bearing power losses.
- Significantly reduce operating temperatures.
- Dramatically increase load capacity.
Oil flow and power loss benefits are obtained by the efficient admission of cool oil to the film.The LEG method of lubrication also allows operation in a non-flooded environment which eliminates parasitic (non-film) losses without risk of starving the oil film. Shoe temperature is lowered by protecting against the effects of hot oil carryover and by reducing parasitic losses between shoes that would add heat to the oil film.The lower shoe temperatures increase the bearing's load capacity.
Kingsbury has used LEG lubrication in field applications since 1985. The applications and data demonstrate that LEG technology is a cost effective and reliable method of lubrication that improves efficiency, lowers capital costs, and adds value to machinery.
Advantages Of LEG Technology
LEG bearings use Kingsbury's original features to ensure optimum load distribution and trouble free operation, and also take advantage of other features such as offset pivots to achieve the best possible performance. Key features make the LEG bearing superior to other directed lubrication bearings in use today:
- Oil feed tubes connecting to the shoes ensure that cool oil does not bypass the film.
- The LEG feature is an integral part of the shoes.
- Large oil flow passages eliminate small-hole clogging.
- No oil seal rings are required, lowering power loss and simplifying design and installation.
- The LEG does not require (but can use) special, higher pressure lube systems typically needed for spray lubrication.
These optimum design and key features are standard on the LEG which contribute to the performance advantages. The LEG bearing's advantages extend beyond performance improvements. Since most of all the fresh oil flows into the oil wedge, the significant reduction in flow and power loss allows 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 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, usually with only minor modifications to the bearing housing. Depending on the operating speed, replacing standard bearings with LEG retrofits will immediately provide advantages regarding oil flow rates, power loss and shoe temperatures. Furthermore, with minor modifications to existing housing parts and flow paths, optimum benefits can be obtained.
For new applications as well as for retrofits, LEG thrust bearings provide the following benefits:
- Lower friction power loss for increased overall machine efficiency.
- Lower operating temperature and increased load capacity.
- Lower oil flow requirements for smaller lubricating oil systems and lower capital costs.
- Ability to optimize for maximum load capacity or to minimize power loss.
Shoes
Kingsbury LEG bearing shoes are designed with offset pivots, 60% of the effective length of the shoe. Standard materials of construction of shoe body are low carbon steel with high tin content babbitt. Material selection can be engineered to meet unusual applications.
Kingsbury utilizes a distinctive raised spherical support on the back of the shoe to allow it to pivot a full 360°, rather than a raised strip which only allows the shoe to tilt in from side to side. Shoe supports are made of carbon tool steel, heat treated to 52 to 57 Rockwell C, to help prevent undue wear of the pivot. Kingsbury tests indicate that this feature allows self-aligning of the shoe, lowering the temperature difference between individual shoes.
Base Ring
Made of structural steel plate or forged steel, the base ring holds the shoes and leveling plates in their operating positions. An oil inlet annulus, at the back of the base ring, distributes oil to axial holes through the base ring outer wall and into the oil feed tube.
Oil Feed Tube
The oil feed tube, connecting the base ring and pad, is designed so that the pad is free to pivot. This not only allows freedom of movement in the pad, but also eliminates the possibility of leakage by directing the oil directly to the pad face.
Leveling Plate Assembly
The equalizing feature of the Kingsbury thrust bearing allows each shoe to carry an equal amount of the total thrust load. The upper and lower leveling plates, working with the spherical shoe supports, ensure that the thrust bearing face becomes perfectly aligned with the rotating thrust collar.
LEG Bearings Outperform Flooded and Other Directed Lube Types
Through exhaustive testing and years of trouble-free operation, Kingsbury's LEG bearing design has proven to be the ultimate in directed lubrication technology. Yet the design concept is remarkably simple.
The bearing shoes and aligning ring are constructed so that cool inlet oil flows from the leading edge groove directly into the oil film. The cool oil in the oil film wedge insulates the babbitt face from the hot oil carried over by 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 the 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.
