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 5: Rolling Element Bearingshere.
Cooling is not needed on pumps with rolling element bearings
Cooling is still found in pumps with high speed and heavily loaded rolling element bearings. But cooling of the oil is very rarely needed and often of no benefit in installations with rolling element bearings. Suppose a cooling jacket restricts the bearing outer ring from free thermal growth in all radial directions. But the bearing inner ring heats up and grows, causing bearing internal clearances to vanish. An excessive preload could result.
Similarly, immersing cooling coils in the oil will cool not only the oil but also the air in the bearing housing. Such cooling then tends to promote moisture condensation and harmful oil contamination. Therefore, cooling water has been deleted from every pump with rolling element bearings at many Best-in-Class (BiC) locations (Chapter 6, Refs. 1 and 5). Since the late 1970s there no longer is cooling water on bearing housings of pumps with operating (fluid) temperatures up to and including 740 degrees o F (394 degrees o C) in modern BiC oil refineries.
Because cooling water ports are shown on a pump drawing the user is led to believe that such cooling is either needed or helpful. Commenting again on Fig. 6.5, when it was discovered that cooling is no longer needed, BiC companies began to leave these cooling water drains open. With modern synthetic lubricants and properly selected rolling element bearings, cooling is no longer used in process pumps. So, irrespective of lube application method, on rolling element bearings cooling will not be needed as long as high-performance synthetic lubricants are utilized.
1. Bloch, Heinz P. and Alan Budris; “Pump User’s Handbook: Life Extension,” (2006) Second Edition, Fairmont Publishing Company, Lilburn, Georgia, ISBN 0-88173-627-9.
5. Bloch, Heinz P.; “Machinery Reliability Improvement,” (1998) Third Edition, Gulf Publishing Company, Houston, Texas, ISBN 0-88415-661-3.