Thrust Bearing - an overview (2023)

Thrust bearings are used for axial positioning of the compressor rotor supporting thrust loads that arise from gas forces within the compressor case.

From: Compression Machinery for Oil and Gas, 2019

Related terms:

  • Olistostrome
  • Tungsten Carbide
  • Impeller
  • Journal Bearing
  • Steam Turbine
  • Thrust Loads
  • Tomography
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Electrical submersible pumps

James F. LeaJr, Lynn Rowlan, in Gas Well Deliquification (Third Edition), 2019

12.3.3 Seal thrust bearing

The thrust bearing location is depicted in Fig. 12.11A for the labyrinth seal type and in Fig. 12.11B for the positive barrier or bag seal type. The bearing consists of a thrust runner, a down-thrust bearing, and an up-thrust bearing, as shown in Fig. 12.14. The thrust runner is keyed to the seal’s shaft, and its position on the shaft is fixed with snap rings. The thrust runner can move up and down between the down-thrust bearing and the up-thrust bearing by a fixed amount. For a 400 series seal the travel between the bearings is approximately from 1.55 to 1.65in.

Thrust Bearing - an overview (1)

Figure 12.14. Typical seal thrust bearing assembly.

Source: Courtesy Valiant ALS.

A down-thrust bearing, thrust runner, and up-thrust bearing are shown in Fig. 12.15. The down-thrust bearing in 400 series seal can carry 6000lbs of thrust at 3500RPM at oil temperatures up to 200°C (392°F). The up-thrust bearing is designed for much smaller loads since a special set of circumstances must occur to place the seal shaft into up thrust. Thrust will be discussed in detail in Section 12.5.

Thrust Bearing - an overview (2)

Figure 12.15. Left to right, seal down-thrust bearing, seal thrust runner, and seal up-thrust bearing.

Source: Courtesy Valiant ALS.

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Andras Z. Szeri, in Encyclopedia of Physical Science and Technology (Third Edition), 2003

II.D.7 Thrust Bearings

Fixed pad is by far the most common thrust bearing configuration (Fig. 21), but fixed pad bearings can accommodate rotation in only one direction, the direction of film convergence. Thus if there is a possibility or a need for reversal of runner motion, pivoted pad thrust bearings must be employed (Fig. 22).

Thrust Bearing - an overview (3)

FIGURE 21. Fixed-pad thrust bearing. [Reprinted with permission from Raimondi, A. A., and Szeri, A. Z. Journal and thrust bearings. In Booser, E. R. (1984). “CRC Handbook of Lubrication,” CRC Press, Boca Raton, FL.]

Thrust Bearing - an overview (4)

FIGURE 22. Pivoted-pad thrust bearing. [Reprinted with permission from Raimondi, A. A., and Szeri, A. Z. Journal and thrust bearings. In Booser, E. R. (1984). “CRC Handbook of Lubrication,” CRC Press, Boca Raton, FL.]

Lubricant pressure in a thrust bearing is governed by the Reynolds Eq. (2). As the film thickness distribution depends on the inclination of the pad to the runner, the nondimensionial load variable will be a function of the slope parameters, mr, mθ. This relationship, which is different for bearings of different geometries, is portrayed graphically in Fig. 23. Looking at it differently, the load conditions determine the equilibrium position of the pad. When in this position, then net torque on the pad must vanish, thus the location of the pivot and that of the center of pressure must be identical. To achieve a design with given load condition and specified pivot position, the designer must employ an iteration procedure involving Figs. 23, 24 and 25.

Thrust Bearing - an overview (5)

FIGURE 23. Load capacity chart for sector thrust-pad (laminar flow). [Reprinted with permission from Raimondi, A. A., and Szeri, A. Z. Journal and thrust bearings. In Booser, E. R. (1984). “CRC Handbook of Lubrication,” CRC Press, Boca Raton, FL.]

Thrust Bearing - an overview (6)

FIGURE 24. Tangential location of center-of-pressure (fixed-pad sector), or pivot position (tilting-pad sector). [Reprinted with permission from Raimondi, A. A., and Szeri, A. Z. Journal and thrust bearings. In Booser, E. R. (1984). “CRC Handbook of Lubrication,” CRC Press, Boca Raton, FL.]

FIGURE 25. Radial location of center-of-pressure (fixed-pad sector), or pivot position (tilting-pad sector). [Reprinted with permission from Raimondi, A. A., and Szeri, A. Z. Journal and thrust bearings. In Booser, E. R. (1984). “CRC Handbook of Lubrication,” CRC Press, Boca Raton, FL.]

Oftentimes the pad is either deliberately crowned or it deforms under the combined action of load and frictional heat. Performance of such pads is still calculated in the manner discussed previously, except that the film thickness distribution now depends not only on the tilt parameters but also on pad deformation. Furthermore, cavitation of the lubricant film within its diverging geometry must be considered.

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Centrifugal Compressors

Jason Wilkes, ... George Talabisco, in Compression Machinery for Oil and Gas, 2019

Condition Monitoring

Compressors and their associated auxiliary systems are instrumented to ensure safety and reliability. Standard alarms, shutdowns, and control systems are discussed in detail within API 614 and API 670 standards. Typical parameters that are monitored online are listed below. Many of these measurements are fed into a machinery protection system. Trips related to overspeed and bearing oil pressure are generally required. Trips related to vibration level and axial position are often specified as well.

Typical Instrumentation


Rotor vibration and position (radial and axial)

Bearing metal temperatures (journal bearings and thrust bearings)

Lube oil console

Lube oil pressure, inlet temperature, and drain temperature

Lube oil differential pressure across the filter

Lube oil level

Lube oil cooling water temperature

Dry gas seal

Seal-gas supply

Vent-gas pressure(s) or flow(s)

Separation-gas pressure of flow

Differential pressure at each filter set

Lube oil cooling water temperature

Compressor performance

Suction and discharge pressure

Suction and discharge temperature

Flow rates

Manual inspections are also of importance. The compressor and the auxiliary equipment should be inspected for leaks at piping connections. Lubricating oil should be periodically checked for the presence of water and for degradation.

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Integrally Geared Compressors

Aaron M. Rimpel, ... Kolja Metz, in Compression Machinery for Oil and Gas, 2019

Thrust Management

It is extremely rare to use a double helical gear in an IG turbomachine because the net pinion thrust (i.e., sum of axial impeller gas forces) would act to load one face of the helical gear more than the other. Therefore, almost all IG turbomachinery use a single helical gear. Furthermore, thrust bearings are almost exclusively fluid film-type configurations with the oil and gas industry. To control the axial position of the large bull gear, a double-acting tapered-land thrust bearing is most commonly applied. The relatively low speed of the bull gear means that minimal fluid shear losses are present in the bull gear shaft thrust bearing.

To control the axial position of the pinion shafts, either thrust collars or thrust bearings are applied. Fig. 4.12 shows a pinion with thrust collars. Thrust collars transmit the net axial force from the aerodynamics and the gear mesh to the bull gear disk axial surface. The net residual thrust is then reacted against the bull gear thrust bearing (a lower speed and lower loss mechanism). The area of the load transmission is relatively small as it is formed by overlapping sections of the outer diameters from the bull gear and a thrust collar on the pinion gear (Fig. 4.13). A hydrodynamic oil film is established to keep the bull gear face separate from the pinion thrust collar. This is similar to a plain thrust bearing, with the difference being that relative motion between the bull gear face and the thrust collar face must be considered as both surfaces are in rotation about different axes. San Andres et al. [10] show an approach to thermal-mechanical and dynamic assessment of thrust collars to understand their performance characteristics.

Thrust Bearing - an overview (8)

Fig. 4.12. Example of pinion gear-shaft with thrust collars.

Courtesy Hanwha Power Systems Americas Inc.

Thrust Bearing - an overview (9)

Fig. 4.13. Thrust collar load area.

Fig. 4.14 shows a pinion shaft and combination journal/thrust bearings. The thrust bearings on the pinion shaft transmit the net axial load from the aerodynamics and gear axial force through the thrust bearing to the static bearing housing. The advantage of the high-speed thrust bearing is that large axial loads can be mitigated; however, this comes at the cost of higher fluid shear losses than a thrust collar.

Thrust Bearing - an overview (10)

Fig. 4.14. Example of pinion gear-shaft with thrust bearings.

Courtesy Waukesha Bearings.

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Marine Engines

John B. Woodward, Tor Erik Andersen, in Encyclopedia of Physical Science and Technology (Third Edition), 2003

VI Dynamic Interaction between Engine and Hull

We have observed that development of marine engines has reached a point where the design of the engine no longer dominates the design of the ship; usually a choice can be made among several engine types, and none will demand a large share of hull volume and lifting capacity. Nonetheless, a ship designer should not design hull and select machinery independently. There are design linkages, such as the effect of engine weight and volume on payload, that have been mentioned earlier.

Possible dynamic interactions are perhaps the most important of all, since poor design can seriously impair the operation of a ship in a way that a minor loss in payload, say, never would. The dynamic interactions arise from the almost inevitable tendency of a propeller to generate torsional, longitudinal, and transverse excitation as its blades rotate through regions of differing water velocity, and from the several sources of excitation within the engine.

If the engine is a diesel, the torque applied to the crankshaft by each piston varies periodically as the cylinder gas pressure varies, and as the inertia forces from piston acceleration vary. If any of the many harmonics of these periodic torques resonates with a natural frequency of the engine-shaft-propeller system, severe torsional vibration may occur. The torsional vibration may be destructive only of the rotating machinery, but by its nature, the propeller is a converter of torque to thrust, and so it is that a strong longitudinal vibration may be caused also.

Longitudinal vibratory forces are transmitted to the hull by the thrust bearing that transmits the propulsive thrust, so that one of the natural frequencies of hull vibration may be excited. A low-speed diesel, in particular, may vibrate longitudinally, acting in the manner of a vertical cantilever beam. If one of its natural frequencies resonates with the frequency of the longitudinal shaft forces, the engine may vibrate excessively, and in turn excite surrounding ship structure.

A reciprocating engine transmits to its shaft bearings the periodic forces that must accompany the periodic accelerations of its pistons and associated moving parts. Usually, however, the forces are canceled through the agency of counterweights on the crankshaft, but it may not be possible to cancel the moments that these forces produce. The degree of moment cancellation depends largely on the number of cylinders, but most typically some significant degree of second-order (meaning frequency equal to twice the rotational frequency of the engine) moment exists. This moment tends to bend the engine vertically about a transverse axis (i.e., bend its ends up and down). Since the engine structure is not infinitely stiff, this bending is transmitted to the engine foundation, and may thereby excite hull vibration.

The phenomena that give rise to these dynamic interactions are largely unavoidable—the pulsing nature of diesel engine torque, for example, is an inevitable characteristic of a reciprocating engine. The principal remedy is to design the moving parts of the engine and shafting system so that resonances between its vibratory modes and the excitations do not occur. In some instances this may include stiffening the engine structure by adding sway braces between the hull and the upper level of the engine (particularly so for the tall low speed diesels). The consequences of unbalanced torques within the engine may be minimized by selecting the number of cylinders for a low moment value, building extra stiffness into the foundation, and by mounting the engine near a node of the expected hull vibration mode.

The smooth torque of turbine engines reduces their dynamic hazard, but unacceptable torsional and longitudinal vibrations can be excited by the propeller. There have also been instances in steam turbines of severe vibration excited by the periodic passage of turbine blades through the steam jets. As with the reciprocating engines, the principal remedy is knowledge of excitations, and of frequencies of vibration, so that resonances can be avoided.

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A review of progress and applications of ship shaft-less rim-driven thrusters

Xinping Yan, ... Jiafen Lan, in Ocean Engineering, 2017

2.2 Bearings used in RDTs

RDTs work in underwater environments, so water-lubricated bearings are best suited to carrying the radial and axial forces of the rotor because of their advantages of environment-friendly, simple structure and no need of sealing device and good compatibility in deformation. Brunvoll, Voith and some other commercial RDTs have successfully used water-lubricated bearings. For hub type RDTs, radial bearings and thrust bearings (e.g., TSL products) can be installed inside and at both ends of the hub. However, for hub-less type RDTs, both kinds of bearings (e.g., Schottel products) can be installed in the duct.

The duct thickness and hub diameter must be as small as possible to ensure favorable hydrodynamic performance of the RDT, which makes the bearing design very complicated. Small size, high load carrying capacity, and wear-resistant water-lubricated bearings have yet to be effectively designed. Especially when the bearing is installed in the duct, the friction arm of the rotor is much larger than when it is installed in the hub, which results in a larger starting resistance torque of hub-less type RDT than that of a same size hub type one. Even in the course of normal operation, the friction loss caused by bearings of hub-less type RDT is greater than that of hub type.

There are two kinds of water-lubricated bearings: Ball bearings and sliding bearings. The hub-less type RDT designed by Kennedy and Holt (1995) used water-lubricated ball bearings, where both edges of the rotor ring were grooved to hold the replaceable plastic bearing races (Fig.17). The use of ambient water-lubricated plastic ball bearings could affect the reliability and longevity of the system, however, as bottom sediments and surrounding water became laden with various size particulates that induced wear on the ball bearings. Various ball and race materials were tested in a stirred sand/water slurry under a 45-lb thrust load at 300rpm to find that urethane balls in ultra-high molecular weight polyurethane (UHMWPE) races perform best after 48-h runs with total wear of only twelve thousandths of an inch.

Thrust Bearing - an overview (11)

Fig.17. Prototype and expanded view of RDT by Kennedy and Holt (1995) from Harbor Branch Oceanographic Institution, Inc. (USA).

Hsieh etal., 2007 manufactured a hub-less type RDT as shown in Fig.18 with ball bearings embedded in the duct, but the rotor could not reach the designated speed at rated voltage supply due to friction in the bearings. Sharkh addressed this problem by installing bearings in (at both ends of) the hub to reduce the friction resistance moment and friction loss.

Thrust Bearing - an overview (12)

Fig.18. Hub-less RDT with ball bearing.

The axial thrust is large in high-power RDTs, and the ball bearing is strained considerably under high loads. Research and development on water-lubricated sliding bearings with elevated load-carrying capacity is necessary. The authors of this paper have conducted extensive research on water-lubricated sliding bearing design and performance optimization for both types of RDTs (Liang etal., 2016; Liu etal., 2015; Ouyang etal., 2016). Fig.19(a) shows a hub type RDT with a water-lubricated polymer sliding journal bearing installed in the hub and two tilting pad thrust bearings installed at both end of the hub. Fig.19(b) shows a tilting pad conical bearing which can be used for both type RDTs. This bearing represents an innovative combination of the journal bearing and thrust bearing that can provide a better cooling water channel for the motor and improve overall cooling performance.

Thrust Bearing - an overview (13)

Fig.19. Water lubricated sliding bearings for RDTs.

Test of the water-lubricated thrust bearings showed in Fig.19(a) has been carried out (Lan etal., 2017). A photo of this kind thrust bearing is shown in Fig.20. According to recent research results, friction between the rotor and bearing is a source of vibration excitation that affects the whole performance of the RDT. The friction pair materials of the water lubricated bearing are the major limiting factors on any improvement to the thrust output.

Thrust Bearing - an overview (14)

Fig.20. Water-lubricated tilting pad thrust bearing for hub type RDT designed by Wuhan University of Technology.

The load carrying capacity and service life of water-lubricated bearings are lower than that of oil-lubricated bearings. Voith (2017) has developed a non-water-lubricated roller bearing system including bio-oil compatibility for its hub type RDTs. The system features a well-proven design and material combination, with bearings equipped with a leakage-free and redundant sealing system. Rolls-Royce also builds oil-lubricated bearings into its newly developed AZ-PM thrusters, which have now already run more than 1500h trouble-free (Rolls-Royce, 2017a,b). The disadvantages of oil lubricated bearings include their structure is complex (especially for thrust bearing), the machining accuracy and installation requirements are high, and reliable sealing devices are needed to prevent the leakage of lubricating oil. According to 2013 Vessel General Permit (VGP) Requirements issued by US Environmental Protection Agency (EPA) and some other regulations enacted by European Union, vessels installed of RDTs using oil lubricated bearings may be prohibited from entering in certain protected waters. These environmental protection laws and regulations may limit the application of oil lubricated bearings on RDTs.

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Recognition of ocean plate stratigraphy in accretionary orogens through Earth history: A record of 3.8billion years of sea floor spreading, subduction, and accretion

T.M. Kusky, ... M. Santosh, in Gondwana Research, 2013

4.1.4 Olistostrome-type OPS

This third type of OPS occurs in southwest Lleyn, is about 20m thick, and consists of many weakly or unmetamorphosed lenses of white quartzite, red chert, dolomitic limestone, and basaltic greenschist embedded in a matrix of black mafic mudstone. Most lenses are 5–30cm across, some reach 6m, and one is 25m long (Maruyama et al., 2010). Kawai et al. (2007) interpreted these rocks as an olistostrome-type mélange (Suppl. Fig.6), which consists of already-formed accretionary material that had slumped down the inner hanging wall of a trench to be incorporated into a gravitational debris flow. The olistostrome is overlain by a phyllonite-bearing thrust and underlain by unbroken ridge–trench OPS.

This third type of OPS occurs in southwest Lleyn, is about 20m thick, and consists of many weakly or unmetamorphosed lenses of white quartzite, red chert, dolomitic limestone, and basaltic greenschist embedded in a matrix of black mafic mudstone. Most lenses are 5–30cm across, some reach 6m, and one is 25m long (Maruyama et al., 2010). Kawai et al. (2007) interpreted these rocks as an olistostrome-type mélange (Suppl. Fig. 6), which consists of already-formed accretionary material that had slumped down the inner hanging wall of a trench to be incorporated into a gravitational debris flow. The olistostrome is overlain by a phyllonite-bearing thrust and underlain by unbroken ridge–trench OPS.

Fig.30 shows a summary of stratigraphic columns of the three types of OPS described above. Study of the OPS provides a viable and valuable means to work out the progressive development of the accretionary orogen in Anglesey–Lleyn.

Thrust Bearing - an overview (15)

Fig.30. Three stratigraphic columns of different types of OPS described in the text. (A) is of the ridge–trench type from the Gwna Group on Llanddwyn island and in SW Lleyn. (B) is the subducted HP type in which basalts have been transformed to mafic blueschists, seen in central Anglesey and on the NW coast of Lleyn. (C). the olistostrome-type of OPS above a unit of ridge–trench OPS, seen especially in Southwest Lleyn (Fig.26).

After Maruyama et al. (2010).

Finally, we point out that understanding OPS can provide important, indeed unique, information on the world's glaciations. Recognition of glacial stratigraphy and structures, necessary for reconstructing for example the Neoproterozoic Snowball Earth, has largely come from tillites that were deposited on-land and on continental margins, and rarely from dropstones deposited in continental slope basins (e.g. Frimmel et al., 2002). However, if there was anything like a global glaciation at the time of the Snowball Earth, then ice or icebergs would have covered many of the deep oceans, enabling ice-rafted dropstones to be deposited in deep-water mid-oceanic sediments, but such oceans have all been destroyed, and there are no reports of dropstones in mid-oceanic sediments. However, theoretically, dropstones should have been deposited in pelagic cherts and mudstones. If we can recognize such pelagic sediments in accreted OPS, then we have a chance to find such glacial debris. Kawai et al. (2008a,b) reported matrix-supported exotic dropstones of sandstone, chert and basalt (arc or continental material from Avalonia) in a 1m-thick hemi-pelagic, mafic mudstone on top of red chert on Llanddwyn Island. The depositional age was estimated to be 595–550Ma, which is coincident with the ca. 580Ma Gaskiers glaciation (Trindada and Macouin, 2007), which from palaeomagnetic data occurred in high- to low-latitudes. The Llanddwyn dropstones are close in age to ca. 590–570Ma diamictites and dropstone beds in Ireland and Scotland, but these occur in continental-based turbidites hundreds of meters thick (Condon and Prave, 2000).

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Glacial geological studies of surge-type glaciers in Iceland — Research status and future challenges

Ólafur Ingólfsson, ... Mark D. Johnson, in Earth-Science Reviews, 2016

4.6 How do crevasse squeeze ridges and concertina eskers form?

The relationships between crevasse squeeze ridges (CSR) and flutes (Sharp, 1985a) suggest there might be more than one mode of CSR formation. Most studies suggest that CSR form as a consequence of sediment infilling basal surge crevasses from the bed upwards and subsequent melting out during quiescence. The mechanics of this process are, however, not entirely clear, mainly because of the lack of detailed sedimentological and geomorphological investigations. Rea and Evans (2011) assessed the potential for the formation of crevasses and their infilling with sediments, using linear elastic fracture mechanics approach and empirical data derived from the literature, for seven surge-type glaciers from Svalbard, Iceland, Greenland and Alaska. They concluded that CSR most likely resulted from the infilling of basal crevasses, driven for the most part, bottom-up, by high basal water pressures. Studies from Svalbard surge-type glaciers have invoked englacial thrusting mechanisms for producing the CSR, suggesting they being derived from debris-bearing thrust faults (Hambrey and Huddart, 1995; Bennett et al., 1996; Glasser et al., 1998). Lovell et al. (2015) found that debris-rich englacial structures observed at surge-type tidewater glaciers in Svalbard display a variety of characteristics and morphologies, which they interpreted to represent the incorporation and elevation of subglacial till via squeezing into basal crevasses and hydrofracture exploitation of thrust faults, reoriented crevasse squeezes, and pre-existing fractures. These structures were observed to melt-out and form embryonic geometrical ridge networks during quiescent phase ice stagnation and ice-margin recession. Cross cutting relationships between flutes and CSR have neither been widely studied nor well explained, and the processes operating between infilling of basal fractures by till and CSR becoming exposed on the foreland during the quiescent phase melting out of dead-ice are not clear. Thorough sedimentological studies, linked to detailed observations of processes operating during surges (Kristensen and Benn, 2012; Lovell et al., 2015), could further highlight the processes explaining the CSR-flute relationships and thus increase our understanding of subglacial ice-flow mechanisms at work during surging.

Although concertina eskers are uniquely associated with surge-type glaciers there are still some aspects as to their formations that are poorly understood. The original explanation of Knudsen (1995) of concertina eskers being formed by compression and deformation of pre-surge englacial eskers has largely been abandoned in favour of them being the result of supraglacial or englacial meltwater deposition in linked cavities or crevasses during or immediately after the surge (Evans and Rea, 2003; Benn and Evans, 2010; Ólafsdóttir, 2011). Along with observations and monitoring of glacier surges, further sedimentological and structural studies of concertina eskers could clarify the processes of their formation in the course of a surge as well as better explaining their spatial pattern.

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