Considerations for Sourcing Parts & Repairs

The pump industry has experienced significant change over the past several decades. As original equipment manufacturers (OEMs) continue to consolidate, many experienced workers in the pump industry are entering the aftermarket world. Independent parts and repair facilities are populated with employees who have 30 years or more of OEM and aftermarket experience. In many cases, this knowledge base includes design and methodology of more than just one OEM. Also, many retirees are serving as consultants, bringing with them a wealth of knowledge and experience. While this may be true of aftermarket services, OEMs possess brand-specific knowledge that is important for optimizing certain systems. Many view the OEM as the safest resource for parts and services. It is up to the end users to investigate all options to determine the best source of parts and services for their specific equipment and applications. When seeking to optimize systems, users should ask the following questions:

• Will the part or repair reflect the most current design and upgrades?
• Can the mean time between repairs (MTBR) be improved?
• How reliable are the quoted lead times?
• What is the price premium to get OEM parts and services?
• Are there qualified and reliable alternatives?

New Technologies

High-energy pumps warrant particular attention to detail and experience. OEMs spend considerable time developing and optimizing the features of high-energy pumps—details that may not be readily apparent when reverse engineering an obsolete or hard-to-get part or refurbishing a pump. More complex pumps, such as segmental ring pumps, may have subtle features such as tapered stationary parts and process specifications that are difficult to duplicate unless a complete, comprehensive inspection is performed. OEMs are understandably protective of their drawing databases. Often, a part must be available in advance of the need to facilitate duplication, which favors OEM supply. For some needs, however, new technologies may provide alternative options. Technologies for reverse engineering obsolete or hard-to-get parts have evolved far beyond scales, vernier calipers and paper. Portable coordinate measuring machines are commonplace and can provide accuracies to less than 0.001 inches. Complex shapes, such as impeller vanes, can be acquired, downloaded to computer-aided design (CAD) software, engineered and then transferred to a computer numerical control (CNC) machine. Creating parts requires product knowledge. Gathering data and manufacturing a part that is worn-out can result in replication of a part that does not reflect the original design. Appropriate redesign must involve knowledge of the basic design, including tolerances, clearances, fits and attention to detail—for example, proper radii to minimize stress concentration factors. Proper material selection ensures that wear parts are anti-galling and corrosion-resistant and that they have proper mechanical properties. Some processes such as heat treatment and non-destructive testing require design knowledge and cannot be determined by inspection. The buyer should review the supplier's quality-control program and inspection documents. Larger jobs may warrant creation of a CAD-generated engineering layout that details all parts and dimensions. The advantages of a layout include a fit-up of the components and a troubleshooting aid for future manufacturing and service needs. Some OEMs have closed domestic manufacturing facilities and have relocated plants overseas. With this change, the ability to provide OEM technical support has diminished in some cases, and lead time can be substantial. As a result, some non-OEMs have developed domestic sources for parts. Users needing cast parts, however, often favor the OEM because the manufacturer typically has the original drawings and patterns. The OEM may be more adequately prepared to answer questions and provide information about specific parts and products. While cast parts can be more challenging for non-OEM suppliers because of the time and cost of gathering the geometry and pattern construction, advanced technology allows companies to more efficiently engineer and manufacture patterns using coordinate measuring technology and rapid prototyping methods. Users requiring large cast parts in small quantities favor the OEM; larger quantities allow the pattern to be amortized. An alternative to large cast parts is a fabrication or weldment, especially for large vertical pump casings, shrouds and columns (typically more than 24 inches in diameter). Materials can be upgraded selectively in high velocity or wear areas. In addition to the components noted, larger impellers can be fabricated, sometimes using cast impeller blades welded to a hub. Fabricated impellers typically do not provide a cost advantage; however, lead times can be greatly reduced.

Case Study

A recent example involved an upgrade to a large circulating pump that required changes in shafting, couplings and enclosing tubes. Disassembly and inspection revealed significant modifications by the user to the cast iron casing (see Image 1) and discharge head because of saltwater-induced corrosion. Comparison to the original design revealed significant changes in lengths, bolting and register fits. The job required inspection of the disassembled pumps, design modifications to accommodate the changes to the pump design, the generation of manufacture drawings, and expediting machining and inspection. The final design confirmed the four customer-modified pumps to a common design with interchangeable parts. Had the parts been sourced from the original OEM records, the interchangeability and final assembly to meet the outage dates may have been compromised.

Conclusion

OEMs provide the advantage of warranty support that encourages long-term business relationships. When sourcing parts or repairs from either the aftermarket or OEMs, the end user must weigh the advantages and disadvantages of each. OEMs classically have the advantage of the original design knowledge and details but may not be as responsive to design variations or quick turnarounds. In the same way, aftermarket experience can provide quick lead times and flexibility, but some companies may not have adequate experience and knowledge. When sourcing parts or repair, end users must do the appropriate research on the possible vendor.