Reverse Engineering of a Vertical Pump Suction Bowl

The pump was returned to service at a nuclear power plant after reverse engineering of an unavailable part and complete pump testing.

Written by:
Jeff Smith, Dr. T. Ravisundar, Werner Barnard
Published:
June 1, 2013

The population of industrial pumps is aging. An article from Pumps & Systems’ August 2012 issue chronicled the repair of an 82-year old pump still in service in a major refinery. Like this refinery, many industrial operations use pumps that have been in service 30 to 50 years or more.

This article presents a case study of a recently refurbished vertical pump. The case study demonstrates how the problem of an unavailable, critical part was overcome through reverse engineering. It also shares the lessons learned and how to develop a strategy to overcome part shortages for old or obsolete pumping equipment.

Critical Part Shortage Identified
A single-stage, vertical pump in a service water application was sent for repair by a nuclear power plant to a qualified, independent pump service and engineering provider. A thorough inspection was performed. Although several important parts had to be reverse engineered and manufactured, all but one were machined parts for which raw material was available. One large cast part, a large aluminum bronze suction bowl weighing more than 500 pounds, was identified as the critical delivery issue.  

Severely Eroded Suction Bowl
Severely eroded suction bowl
Photo courtesy of Hydro Inc.

 

Modern Technology applied
The independent service provider had a skilled, in-house engineering team that used process control procedures for reverse engineering under its Nuclear Procurement Issues Committee (NUPIC) audited quality assurance program. This service organization understands that reverse engineering is not the same as replicating. The service center’s engineering team evaluated the critical characteristics of the component, which is an essential step in developing a replacement part that will meet the same form, fit and function as the original.

The engineers started the process by producing a 3-D model and a 2-D drawing of the suction bowl, capturing the part’s geometry with the aid of a state-of-the-art coordinate measurement machine (CMM).

The portable CMM, with a seven-axis articulation and equipped with both contact and non-contact (laser) probes, enabled the engineers to quickly capture the dimensions of the suction bowl with high precision. To address the missing geometry of the eroded vanes, an engineering analysis was performed to reconstruct the original geometry. With this information, a 3-D model was created. In addition to measuring the geometry of the part, all the critical characteristics—such as hardness, chemical composition, surface finish, fits and tolerances—were evaluated.

The reverse engineered data of the bowl’s hydraulic passageways was then thoroughly reviewed. This included vane-to-vane distance, vane curvature from the leading edge to the trailing edge, hub and shroud curvature, vane thickness distribution, and all other critical dimensions. The hydraulic contours of the 3-D model were then smoothed without significantly affecting the original geometry, and the vane thickness distribution was made uniform. The 3-D model developed for the casting was completed by adding machining allowances for bores, flange outer diameters and faces.

Once the 3-D model for the casting was complete, the service provider’s engineers worked with a reliable foundry known for producing excellent aluminum bronze castings to develop a manufacturing and quality plan to cast the replacement suction bowl. With a thorough understanding of the latest rapid casting processes, the engineering team created a casting plan that included a layout for the risers, gates, runners, sprue and other mold package details. This plan was engineered using solidification simulation software so the engineers could determine the optimal layout for the mold package. A well-designed mold package reduced the risk of a failed casting and maintained the rebuild schedule.

Solidification Simulation
Solidification simulation
Image courtesy of Hydro Parts Solutions Inc., a Hydro Company

 

Once the casting plan was complete, the 3-D model was used to make a large, sand-printed mold package. The mold package consisted of several mold pieces and a large core for creating the intricate details within the bowl. This modern technology allowed the service provider to produce a successful casting in a timely manner without a hard pattern or core box.

Typical sand-printed core
Typical sand-printed core
Image courtesy of Hydro Parts Solutions Inc., a Hydro Company

Inspection and Testing
The cast suction bowl was sent to the service center for inspection by the quality assurance team. The chemical and physical characteristics were analyzed and found to be within the American Society for Testing and Materials (ASTM) ranges. It was also observed that the casting’s surface finish and dimensional accuracy was superior to that of conventional castings for the given material.

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