A Hydro East welder repairs the impeller of a Foster Wheeler circulating water pump.

During the 2012 refueling and maintenance outage at Unit 1 of the two-unit Calvert Cliffs nuclear power plant, near Lusby, Md., Hydro East, a subsidiary of Hydro Inc. based in Aston, Pa., supported the on-site overhaul of two large circulating water pumps. Used to supply cooling water to the plant, the Foster Wheeler vertical pumps are 8 ft 3 in. in diameter, 11 ft 5 in. tall, and weigh approximately 25,000 lb.

After the 2012 refueling outage was completed, Calvert Cliffs engineers and Hydro East’s field service team convened to discuss the project, review lessons learned, and generate plans for making the 2013 refueling outage at Unit 2 even more efficient and cost-effective. In preparation, the two groups reviewed the process that had been used in 2012 to remove, rebuild, and reinstall the Unit 1 circulating water pumps, which had been rebuilt on-site. Hydro East’s field service technicians reconditioned the impellers on location, and the Fort Smallwood Fabrication Shop gathered the other parts required to complete the rotating assemblies. The complete disassembly of an entire pump took four 12-hour
shifts, requiring one shift to clean all the reusable parts and another shift to flip and stage the parts. Each shift required a significant number of site resources as well—including security, a crane, and the crane operator—and because other tasks being performed during the outage required the use of some of these same resources, the field service technicians experienced substantial downtime.

To eliminate downtime caused by plant-induced delays—such as having to wait for the crane to become available or for spare parts to be machined—Calvert Cliffs decided to remove the Unit 2 circulating water pump rotating assemblies in one piece and send them to the Hydro East service center to be rebuilt. This plan enabled Calvert Cliffs to achieve cost savings by maximizing the availability of its internal resources and by reducing the number of shifts needed to remove
the pump assemblies from four 12-hour shifts to two. More important, lifting the assemblies in one piece eliminated two high-risk rigging activities for each pump.

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Reverse Engineering: A Strategy for Solving Critical Part Shortages

The population of industrial pumps is aging. An article from Pumps & Systems’ August 2012 issue chronicled a repair done on an 82-year old pump still in service in a major refinery (click here to read that article). Like this refinery, many industrial operations are using pumps that have been in service 30 to 50 years or more. It is clear the infrastructure of industry is at risk due to the lack of planning by the pump owners and the more limited support from the companies that provided the pumps. To be fair to the pump OEMs, these pumps have been kept in service much longer than a pump OEM would have originally anticipated.

This article will present a case study of a recently refurbished vertical pump, show how the lack of a critical part was overcome through reverse engineering, and will share lessons learned for developing a strategy to overcome part shortages for old or obsolete pumping equipment.

Critical Part Shortage Identified

This single-stage vertical pump in a service water application was sent for repair by a nuclear power plant to Hydro Inc., a reliable independent pump service and engineering provider. A thorough inspection was performed, and 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.

Hydro has a highly-skilled in-house engineering team that utilizes process control procedures for reverse engineering under their NUPIC-Audited Quality Assurance Program. Hydro’s organization is one that understands that reverse engineering is NOT the same as “replicating”. Hydro’s engineering team evaluated the critical characteristics of the component, which is essential to developing a replacement part that will meet the same form, fit, and function as the original.

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A nuclear power plant required field service support for their high energy multi-stage diffuser barrel pump when a feeler gage became lodged inside the pump element. The station had been experiencing a problem with a lube oil pump and the decision was made to flush the lube oil lines. During this process, the plant’s maintenance team recognized that the charge pump’s inboard pump bearing housing dowels had been bent and the rotor was not properly centered on the inboard end. As Murphy’s Law dictates, “anything that can go wrong, will go wrong”. While the rotor was being centered, a feeler gauge that had been left in the element broke off and became stuck in the inboard end at the first-stage wear ring between the inboard impeller shroud and cover wall.

The rotor had shuttled and rotated a considerable amount during the original attempt to remove the broken remnant. The station contacted a reliable pump aftermarket service provider who had a highly-skilled field service team with the knowledge and experience to provide support. The station wanted to get this pump back online quickly and asked the field service team to work around the clock to retrieve the broken material and complete the pump assembly. The field service team collaborated with the station’s maintenance team to resolve the issues and get the pump back into service.

A bore scope was used to confirm the piece could not be easily extracted without removing the element. The Technical Field Advisor submitted to the station an Element Removal and Installation Procedure which defined the steps for retrieving the broken feeler gage and properly installing the element back into the barrel. Upon approval of the procedure, day and night shifts were scheduled to resolve the issues.

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