Thrust Bearing Failures

EiTatic high-frequency vibration amplitude and possibly an audible sound. Rotor mb Labyrinth mbs generally self-comect Disc mbs due to thrust bearing failure often self-comect temporarily through wean steel on steel shrill noise during wear Rotor deflection is critical speed... 

The axial transducers should have one probe sensing the shaft itself within 12 inches (305 mm) of the active surface of the thrust collar with the other probe sensing the machined surface of the thrust collar. The probes should be mounted facing in opposite directions. Temperature probes embedded in the bearings are often more useful in preventing thrust-bearing failures than... 

Most hydrocarbon gases are more soluble in cold oil than in hot oil and may lower the viscosity to a dangerous level. The problems of thrust-bearing failures during startup due to low-viscosity oil can be eliminated by equipping the reservoir with oil heaters to raise the oil to the normal operating temperatures before starting the machine. 

Cleaning also prevents failures due to abnormal operating modes. Fouling of the rotor blades on turbines can cause thrust-bearing failures. Deposits on... 

A thrust-bearing failure is one of the worst things that ean happen to a maehine, sinee it often wreeks the maehine, sometimes eompletely. To evaluate the reliability of a thrust-bearing arrangement, we must first eonsider how a failure is initiated and evaluate the merits of the various designs. 

A critical installation should have the metal temperature sensors in the thrust pad. Axial proximity probes may be used as a backup system. If metal temperatures are high and the rate of change of those temperatures begins to alter rapidly, thrust-bearing failure should be anticipated. 

Other items unique to steam turbines that must be considered are water carryover and fouling. Carryover can leave deposits on the blading, causing loss in performance and increased thrust loads. If carried to an extreme, thrust bearing failure could occur. If a large amount of water is carried over as a slug of liquid, catastrophic failure can occur. 

Elimination of potential thrust bearing failure due to failure of the large diameter balance piston labyrinth. 

It is important to seal the glands on the turbine shaft, and a typical arrangement is illustrated in Figure 14-24. Thrust bearing failures can be serious problems for steam turbines and other mechanical drives, as well as the bearings used on the driven equipment. 

Failure protection. Fortunately, aeeurate and reliable instrumentation is now available to monitor thrust bearings well enough to assure safe eontinuous operation and to prevent eatastrophie failure in the event of an upset to the system. 

Kale.R.D. et al - Analysis of failure of Axial Thrust Balancing and Thrust bearing of a small capacity boiler feed pump for a nuclear power plant, IV Asian International Conference on Fluid Machinery, Oct 1993, China. 

We determine the failure probability of a fluid bearing using the common definition utilized for mechanical structures namely stress-strength relationship. The equivalent of the strength for a fluid bearing is the maximum load capacity which can be supported by the film fluid taking into accoimt the optimum of stif iess obtained. In this condition, the fluid film gap is very small (lower than 10 fjum for air thrust bearings) and a soUd contact is possible if an imstable state appears. 

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