Thrust bearing

Thrust bearings are meant to keep a rotating shaft from motion parallel to the axis of rotation. Various configurations are possible, but the most common is one in which the load is supported by the bearing in a vertical shaft system. 

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Table 4. Teflon PFA Fluorocarbon Resin Thrust-Bearing Wear-Test Results ...

Back-to-back impellers allow for a balanced rotor thrust and minimize overloading the thrust bearings. 

Balance piston with no external leakage will greatly reduce wear on the thrust bearings. 

Nonequalizing tilting pad thrust bearing with radial pivot... 

Thrust-Bearing Power Loss The power consumed by various thrust bearing types is an important consideration in any system. Power losses must be accurately predicted so that turbine efficiency can be computed and the oil supply system properly designed. 

Figure 10-123 shows a typical power consumption in thrust bearings as a function of unit speed. Tne total power loss is usually about 0.8-10 percent of the total rate power of the unit. New vector lube bearings reduce the horsepower loss by as much as 30 percent. In large vertical pumps, thrust bearings take not only the load caused by... 

Thrust Bearings Turboexpanders often have process upsets or ice plugging or the hke, which can cause serious thrust-bearing load variations. In applications above 506.6 to 1013.2 kPa (75 -148 psi), the best available thrust bearing usually is insufficient to protect against such high thrust loads. Various indicatious, such as the differential... 

Thrust-bearing-load meters for protection against excessive loading are available on thrust bearings, and automatic thrust control, which functions by controlling the pressure behind a balancing drum, also is available. 

Rotor Seals To balance the thrust on the rotor, usually there are one or two labyrinth-type seals on the rotor. These seals often are damaged if there is dust in the incoming fluid or gas, and wear on the backside seal causes serious upsets in thrust-bearing loads. Provisions are available for coUecting and disposing of the dust which tends to accumulate in the seal so as to protect the seal from serious erosion. 

Usually, a journal bearing and a thrust bearing are combined in one assembly, and oil is injected so as to feed both of them. The rate of flow usually is adjusted so as to carry the heat away with a temperature rise of the order of II to 17° C (20 to 30° F). 

These motors have a lower efficiency as a result of running in liquid, causing more liquid drag and also axial thrust bearing loss, which is also a part of the motor. However, this lower efficiency of the motor is compensated by fewer mechanical and hydraulic losses in a submersible motor-pump installation, compared to a vertical turbine pump installation. 

Motor bearing bush Thrust bearing ring... 

For sliding contact bearings (sleeve or thrust bearings) the temperature readings mtisl be taken from as near to the bearing stirface as possible. 

There should be enough space between the coupling halves so that they don t touch should the motor shaft move forward toward the pump. This space should also consider movement due to wear in the pump thrust bearing. The coupling manufacturer specifies the minimum... 

A paper mill was using an ANSI end suction process pump with clear water service. The motor was designed properly. The pump axial thrust bearing ran hot, failing after three months of operation. It was replaced with an identical bearing. This ran during three months and also failed. All pump components were investigated and found that they complied with the specifications. These facts eliminated the defects of materials as a cause. 

Centrifugal (radial inflow) turboexpanders are well adapted to such energy conservation schemes and, with recent developments that have increased their reliability, are suitable for unattended service on a 24-hour, 7-day week operational basis. Some of the recent developments include better shaft seals, thrust bearing monitoring, and superior control devices. 

In intermediate and larger sizes the thrust bearing problem requires more attention, but it has been effeetively solved reeently by the introduetion of the thrust foree meter and thrust foree adjustment valve, deseribed earlier. 

Thrust bearings, often the most problematie eomponent in highspeed maehinery, ean be aeeurately monitored and eontrolled. 

Figure 2-11 illustrates the potential severity of three problems that tend to eorrelate turboexpander inlet pressure thrust bearings, erosion of rotor and nozzles, and radial bearings. 

The Automatie Thrust Balanee System is a dynamie adjusting system. Hydrodynamie pressure at the thrust bearing faee, an indieation of thrust loads, is eontinuously monitored and fed to either side of a piston, whieh, in turn, adjusts the pressure aeting behind the eompres-sor wheel. 

The maximum outer diameter of thrust bearing (based on thrust collar design and allowable stresses)... 

Axial length of thrust bearing (given by manufacturer)... 

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