Proper lubrication of compressors and centrifugal pumps is a subject that’s both vast and of great importance. Because uninterrupted long-term operation is especially critical in oil refineries and petrochemical plants, we’ll focus attention here on issues observed in fluid machines such as gas compressors and centrifugal process pumps in this specific industry sector.
When you examine design and fabrication in greater detail, you realize that flow, pressure capabilities, and construction materials are given far more attention than lubricant application, lubricant selection, and bearing protection. A similar observation can be made on mechanical seal selection, where savings in initial cost and the desire to link up in a vendor or supplier alliance often crowd out the quest for true long-term reliability achievement.
Introduction to risky components: Oil rings. Reliability-focused user companies are intent on designing out maintenance and avoiding—even disallowing—subassemblies or machine elements that are prone to malfunction. Figure 1 serves to make the point by showing widely used oil rings as originally installed (left image) and as removed from a bearing housing (right image) after leading to a bearing defect. Unless oil rings are designed and manufactured with heat-stabilized (annealed) materials, they will not remain sufficiently concentric to preclude slipping and skipping on shafts. An out-of-roundness exceeding 0.002 inches (0.05 mm) is not considered acceptable for oil rings. That fact alone mandates manufacturing and intermediate stress-relieving procedures which, by their very nature, exclude the use of lowest-cost products.