Explore key facets of centrifugal pump ownership, installation, operation, and troubleshooting
The Second Edition of Pump Wisdom: Essential Centrifugal Pump Knowledge for Operators and Specialists delivers a concise explanation of how pumps function, the design specifications that must be considered before purchasing a pump, and current best practices in lubrication and mechanical seals.
This new edition also contains new startup and surveillance tips for pump operators, as well as repair versus replacement or upgrade considerations for maintenance decision-makers, new condition monitoring guidance for centrifugal pumps, and expanded coverage of operator best practices.
Read Chapter: 4 Piping, Stationary Seals and Gasketinghere.
Radial vs. axial (thrust) bearings
In pumps designed and marketed in the United States, the radial bearing is usually configured as illustrated in Fig. 5.4, although European pump designs generally favor the higher load-rated cylindrical roller bearing.
Higher initial cost and the need for more careful assembly are the distinguishing characteristics of cylindrical roller bearings as compared to typical ball bearings. Regardless of bearing style, the bearing in the radial location should be free to move axially, whereas the outer rings of a thrust bearing assembly should be restrained in place. However, applying an excessive clamping force would risk distorting or buckling the outer ring. Allowing the thrust bearing set to axially move as much as 0.002 in (0.05 mm) ensures there is no unduly large clamping force.
Although called thrust bearing, bearings at the thrust location in pumps are generally absorbing loads in both the axial and radial directions. A double-row thrust bearing is shown in the ANSI (standardized dimension) process pump of Fig. 5.5. The thrust bearing in this illustration is a double-row angular contact bearing (DRACB) with a single inner ring.
A double-row bearing with two separate inner ring halves is available for applications where somewhat higher loads must be accommodated. The castellated (cog-type) clamping nut and tab washer shown in Fig. 5.5 are required to secure the two inner rings of a double-row bearing to the shaft.