Extending the Life of Pump Bearings


Written by:
Mike Petrashko, NSK Corporation

Pumps and Systems, July 2009

The initial cost of a pump is a small component of the pump's total life cycle cost. Progressive, proactive maintenance practices are vital to maximize pump life, minimize downtime and avoid costly repairs and lost production.

lifecyclecosts

Figure 1. Typical centrifugal pump life cycle costs

Rolling element bearings are also an important component for extending a pump's life. Proper bearing selection in designing, servicing or retrofitting pumps can significantly reduce maintenance costs and elevate product value for end users. Pump bearings should meet and ideally exceed pump standards (such as ANSI/API 610, ISO 13709:2003 and Hydraulic Institute standards)

Pump bearing life can be extended without modifying the pump. Retrofitting rotating shaft systems in the field with new advanced rolling bearings increases reliability and safety and can be achieved without changing the bearing size or modifying the pump.

Advanced bearing technologies such as highly pure steels, advanced heat treatments, optimized contact angles and geometric features can extend bearing fatigue life up to five times that of conventional bearing fatigue life without changing the bearing size to reduce warranty, maintenance intervals and cost per service..

Advanced Bearing Technologies

High Purity 52100 Steel for Centrifugal Pump Bearings

Typical rolling element bearings used for centrifugal pumps are radial ball bearings, angular contact bearings, double row ball bearings and cylindrical roller bearings in various arrangements. Apart from more expensive and exotic bearing materials for unique pump applications, centrifugal pump bearings primarily use bearings made of SAE 52100 steel.

The steel's physical and mechanical properties are critical to developing long life in rolling element bearings. Variation and processing of SAE 52100 bearing material significantly affect the empirical data compared to actual application bearing life (see Figures 2 through 4).

 

Carbon 0.98
Chromium 1.3-1.6
Iron Balance
Maganese 0.25
Phosphorus 0.025 max
Silicon 0.15-0.35
Sulphur 0.025 max

Figure 2. Chemical Composition of 52100 Bearing Steel

 

Density (lb/cu. In.) 0.283
Specific Gravity 7.83
Specific Heat (Btu/lb/Deg F - {32-212 Deg F}) 0.114
Melting Point (Deg F) 2595
Thermal Conductivity 240
Mean Coeff Thermal Expansion 6.5
Modulus of Elasticity Tension 29

Figure 3. Physical Properties of 52100 Bearing Steel

 

  Temperature (C ˚/F ˚)

 

  21 ˚C/70 ˚F 200 ˚C/390 ˚F 400 ˚C/750 ˚F

 

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