Aug. 25, 2025
As with any industry, the search for simpler and lower maintenance solutions is an ongoing pursuit to improve the bottom line. The turbomachinery industry is no exception. Tilt pad bearings are often used in these applications for their ability to operate at high speeds; however as with any lubrication-based system, maintenance due to wear caused by friction must always be factored into the ability to meet production goals. New WayⓇ offers an alternative to minimize maintenance with a non-contact solution. New Way’s precision radial bearings provide a frictionless solution through its keystone Porous Media TechnologyTM, utilizing pressurized air or gas to ensure consistent performance every time.
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New Way has been manufacturing air bearings for the machine tool, semiconductor and wafer manufacturing, and medical industries for 25 years. Recognizing the need for Frictionless Motion®️ in the turbomachine industry, we developed a solution, leveraging our porous media technology we pioneered for linear usage, and placing it along the outer diameter of a curves surface. The result is our radial bearings and balance bearings, ideal for supporting a rotating artifact in such applications as:
Tilt pad bearings are prominent in the turbomachinery industry because of their ability to operate at high speeds without causing whirl in certain configurations. While they are able to meet rigorous operating requirements demanded by the turbo industry, this comes at a cost in maintenance and complexity, ultimately affecting profits. Let’s look at five areas where New Way’s radial bearings for turbomachinery are able to overcome obstacles inherent to the tilt pad bearing design.
1. Zero Friction
Friction plagues engineers because of its effect on equipment life, precision, speed, and the oil /lubrication requirements it demands. Tilt pad bearings require oil lubrication systems to manage friction during operations.
In addition to zero friction during operation, radial air bearings use of an external supply of gas that provides zero friction at start/stop, a known deficiency with tilt pad bearings.
2. Precision
Tilt pad bearings require careful design of a series of typically three to six curved pads, each of which can move around a pivot, line, or point. The clearance between the pad and the shaft must be understood and monitored to achieve the desired precision level. This requires complex monitoring software factoring in the number of pads, pre-load, pivot offset, and the direction of the load. The sheer number of components to consider make nano-precision accuracy cumbersome and challenging to achieve.
New Way’s Porous Media’s sub-micron holes allow for even distribution of air across a single face, simplifying attainment of the desired accuracy, as compared to tilt pad bearings. This fact, coupled with zero friction (including start/stop,) allow porous media bearings to operate to nano-precision positioning consistently, making it more reliable and precise. This is a key discriminator of Externally Pressurized Porous (EPP) Gas Bearing Technology in meeting the demand for increased precision of radial bearings in the turbomachine industry/
3. Wear
While lubrication minimizes friction, it cannot completely eliminate it, particularly at start/stop where contact is made. As a result, lubrication-based bearings like tilt pads, experience wear, eventually resulting in maintenance downtime.
The use of EPP Technology in radial bearings equates to no moving parts and no contact (even at start/stop.) The end result is consistent performance and less maintenance, yielding greater production.
4. Speed
For tilt pad bearings, speed is yet another item to consider in its complicated monitoring software. A change in speed must consider the impacts on other aspects of the system (e.g. movement of pads, temperature implications, etc.)
While tilt pad bearings are known for their ability to operate at high speeds, porous media air bearings are also capable of operating at high speeds, yet with a simpler methodology. Given there is no contact and no moving parts, the EPP Technology in New Way products offers a straightforward approach to reaching comparable high speeds.
5. Heat Generation
Heat generation can induce wear and impact operations requiring maintenance downtime. One of the disadvantages of tilt pad bearings is the heat generation created as a result of the sheer number of moving pieces, directly impacting the viscosity of the oil lubricant. This thermal relationship is another factor in the complex equations required to operate tilt pad bearings to meet the desired performance. In some instances, costly cooling systems are required.
Porous media bearings inherently have less heat generation since there are fewer moving components. EPP Technology creates gas across an even porous surface as compared to oil across multiple moving surfaces affected by heat and viscosity changes. While a thermal relationship still needs to be monitored, it is greatly simplified. An external pressure supply allows the input pressure to easily be modified to create a gap, affecting the temperature, if necessary. Our bearings minimize heat generation and provide streamlined methods for managing temperature changes, resulting in less maintenance downtime and longevity of operating equipment.
New Way provides a range of precision radial bearings in varying sizes, as well as custom solutions. In addition to radial bearings, we also manufacture thrust bearings for axial/thrust loads which can be used as an alternative to tilt pad oil bearings. A special subset of our radial bearings are the balance bearings. Hard or soft mount compatible, the Balance Bearings balance shafts without contacting hard rollers. New Way’s design improves rotor-balancing through proven EPP Technology. Don’t worry if you aren’t designing from scratch! Balance Bearings can be retrofitted to existing machinery.
Tilting pad thrust bearings are designed to transfer high axial loads from rotating shafts with minimum power loss, while simplifying installation and maintenance. The shaft diameters for which the bearings are designed range from 20 mm to more than 1,000 mm. The maximum loads for the various bearing types range from 0.5 to 500 tons. Bearings of larger size and load capacity are considered nonstandard but can be made to special order.
Each bearing consists of a series of pads supported in a carrier ring; each pad is free to tilt so that it creates a self-sustaining hydrodynamic film. The carrier ring may be in one piece or in halves with various location arrangements.
Two options exist for lubrication. The first is to fully flood the bearing housing. The second, which is more suitable for higher speed applications, directs oil to the thrust face. This oil is then allowed to drain freely from the bearing housing.
Similarly, two geometric options exist. The first option does not use equalizing or leveling links (Figure 1). This option is used in many gear units and other shaft systems where perpendicularity between shaft centerline and bearing faces is assured.
Figure 1. Flooded Lubrication:
Typical Double-thrust Arrangement
Bearings for both flooded and directed lubrication are intended for machines where an equalized thrust bearing is specified by API requirements, or where the bearing may be required for other reasons.
The conventional method of lubricating tilting pad thrust bearings is to flood the housing with oil, using an orifice on the outlet to regulate the flow and maintain pressure. A housing pressure of 0.7 to 1.0 bar (10.1 to 14.5 PSI) is typical, and to minimize leakage, seal rings are required where the shaft passes through the housing.
Although flooded lubrication is simple, it results in high parasitic power loss due to turbulence at high speed. Where mean sliding speeds in excess of 50 meters per second (m/s) are expected, these losses may be largely eliminated by employing the system of directed lubrication. As well as reducing power loss by typically 50 percent, directed lubrication reduces the bearing temperature, and in most cases, oil flow.
Some typical double-thrust bearing arrangements using directed lubrication are shown in Figure 2.
Figure 2. Directed Lubrication: Typical Double-thrust
Arrangements Designed to Prevent Bulk
Oil from Contacting the Collar
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It should be noted that:
Directed and flooded bearings have the same basic sizes and use identical thrust pads.
Preferred oil supply pressure for directed lubrication is 1.4 bar (20.3 PSI).
Oil velocity in the supply passages should not exceed three meters per second (m/s) to ensure full pressure at the bearing.
The bearing housing must be kept free of bulk oil through an ample drain area around the collar periphery.
No seal rings are required on the shaft.
Manufacturers offer a variety of pad materials. Some polymeric materials are capable of operating at temperatures up to 120°C (248°F) higher than conventional white metal or babbitt. Also, pad pivot position can have an effect on thrust pad temperature.
All pads can be supplied with offset pivots, but center-pivoted pads are preferred for bidirectional running, foolproof assembly and minimum stocks. At moderate speeds, the pivot position does not affect load capacity; however, where mean sliding speeds exceed 70 m/s, offset pivots can reduce bearing surface temperatures and thus increase load capacity under running conditions.
Thrust bearings can be fitted with temperature sensors, proximity probes and load cells.
In hydraulic thrust metering systems, a hydraulic piston is located behind each thrust pad and is connected to a high-pressure oil supply. The pressure in the system then gives a measure of the applied thrust load. Figure 3 shows a typical installation of this system complete with control panel, which incorporates the high-pressure oil pump and system pressure gauge calibrated to read thrust load.
Figure 3. Hydraulic Thrust Metering
Arrangement
For systems incorporating load cells or hydraulic pistons, it is typically necessary to increase the overall axial thickness of the thrust ring.
Finally, thrust bearings incorporate hydraulic jacking provisions. These provisions ensure that an appropriate oil film exists between thrust runner and bearing pads while operating at low speeds.
At startup, the load-carrying capacity of tilting pad thrust bearings is restricted to approximately 60 percent of the maximum permissible operating load. If the startup load on a bearing exceeds this figure and a larger bearing is not an option, the manufacturer can supply thrust bearings fitted with a hydrostatic jacking system to allow the bearing to operate with heavy loads at low speeds. This system introduces oil at high pressure (typically 100 to 150 bar (1,450 to 2,175 PSI) between the bearing surfaces to form a hydrostatic oil film.
It should be noted that a similar approach is taken when making hydraulic jacking provisions for radial bearings. A hybrid thrust bearing is offered by Kingsbury and Colherne Company (based in the United Kingdom) under the name KingCole.
The bearing housing requirements for the KingCole LEG bearing are similar to those of standard thrust bearings. Oil seals at the back of the carrier rings are not required because the inlet oil is confined to passages within the base ring assembly. Fresh oil enters the bearing through an annulus located at the bottom of the base ring. The discharge space should be large enough to minimize contact between the discharged oil and the rotating collar. The discharge oil outlet should be sized so that oil can flow freely from the bearing cavity.
The manufacturer recommends a tangential discharge opening, equal in diameter to 80 percent of the recommended collar thickness. If possible, the discharge outlet should be located in the bottom of the bearing housing. Alternatively, it should be located tangential to the collar rotation. The bearing pads and carrier ring are constructed so that cool undiluted inlet oil flows from the leading edge groove in the bearing pad directly into the oil film. The cool oil in the oil film wedge insulates the white metal face from the hot oil carryover that adheres to the rotating collar.
In contrast to the LEG bearing, the oil for spray-fed bearings is injected between the bearing surfaces, not directly on them. This can result in uneven bearing lubrication and the need to supply nonpractical high pressure to achieve true effective scouring of the hot oil carryover adhering to the thrust collar. There is also a possibility for the small jet holes to clog with foreign material.
Friction power loss is claimed to be lower than both flooded and spray-fed bearings due to the reduced oil flow. The flow of cool oil over the leading edge lowers pad surface temperatures and increases the KingCole’s capacity.
The resulting performance improvements are shown in Figure 4.
Figure 4. LEG Bearings vs. Standard Flooded Bearings and Spray-fed BearingsAssuming an oil inlet temperature of 50°C (122.4°F), it is possible to estimate the white metal temperature of KingCole leading edge bearings from Figure 5. These temperatures are a function of surface speed and contact pressure.
Figure 5. LEG White Metal Temperatures at 75/75 Position (6- and 8-pad series, steel pads)Thrust load, shaft RPM, oil viscosity and shaft diameter through the bearing determine the bearing size to be selected.
Leading edge bearings are sized for normal load and speed when transient load and speed are within 20 percent of normal conditions.
All curves are based on an oil viscosity of ISO VG32, with an inlet oil temperature of 50°C (122.4°F). The manufacturer recommends ISO VG32 oil viscosity for moderate- through high-speed applications.
Table 1.
Thrust Bearing Designation
Numbers and Bearing Area
(KingCole 8-pad thrust bearings)
The basic principles of tilting pad journal bearing operation are explained in the selection guides and related literature of many competent manufacturers. One of these is Waukesha Bearings of Waukesha, Wisconsin.
Sources
The Glacier Metal Company in London, England and Mystic, Connecticut; Kingsbury Inc. in Philadelphia, Pennsylvania and Waukesha Bearings in Waukesha, Wisconsin.
Editor’s Note:
This article was published in Heinz Bloch’s book, Practical Lubrication for Industrial Facilities. This and other lubrication-related books are available through Noria's Online Bookstore.
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