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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Often all that is needed to improve a pump’s reliability and performance is to provide a high quality inspection and repair. Over time a pump may have been repaired by more than one service provider with varying levels of engineering and technical experience. Tolerances may have been opened up, fits and concentricities may have been lost and materials may have been changed, all of which contribute to reduced performance, loss of reliability and more frequent repairs.

This article highlights the opportunity seized by a coal-fired power station to upgrade a Westinghouse Vertical Pump during the repair process.

Background:

The Power Plant’s Unit #4 “Alpha” Circulating Water Pump was scheduled for repair and in the process of removal, the sister pump #4 “Bravo”, exhibited severe vibration and failed in a manner which was believed to have been a result of a broken shaft. The Alpha pump was put back into service and the Bravo pump removed and sent to the repair facility for inspection and emergency repair.

Observed Pump Condition:

The general condition of the Bravo pump when received at the repair facility was much worse than anticipated with the top column flange broken about half way around. The entire pump had been hanging from this broken joint leaving a gap of ¼” to ½” at the opening. The keyed coupling (internal to the pump) used to join its two shafts was broken in several pieces, the shaft journals were severely worn to one side and the impeller vanes & suction bell liner surface were also severely worn as expected, considering the significant pump damage.

After disassembly of the pump, it was also observed that the shaft enclosing tubes had spun in their fits due to not being fitted with any anti-rotation mechanism. This rotation caused damage to the ‘O’-ring fit areas at both ends of the enclosing tube assembly resulting in loss of proper flush water supply to the pump bearings below the packing box. Another issue observed during inspection was that part-to-part alignment of major pump components utilized dowel pins, which are very difficult, if not impossible, to verify.

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