Close Inspection Solves High Thrust Bearing Temperature Problem

Careful analysis identified the issue with this multistage, oil transfer pump.

Written by: Gary Dyson (Hydro, Inc.)
Publisher: Pumps & Systems / August 2014

 

A multistage BB5 diffuser machine in oil transfer service in the Middle East had been in operation for many years without problems. After a routine maintenance strip down and rebuild, the pump experienced a high thrust bearing temperature of 105 C, which caused it to alarm and shut down. The temperature range had previously been 75 C to 85 C.

This case study describes the method used to solve the high bearing temperature problem and outlines the flow physics that contributed to the high thrust bearing temperature. The customer contacted an engineering services company after the original pump manufacturer failed to remedy the problem.

The company’s forensic approach to this problem involved two distinct methodologies:

  • Diligent and in-depth analysis of site data relating to 
the problem
  • Rigorous scrutiny and analysis of the pump geometry and build against the background

The engineering services company identified several scenarios that could cause this temperature rise, then narrowed down the list to establish a root cause.

Site Data Analysis

The behavior of thrust bearing pads during startup is seldom investigated. The temperature rise of the pads can be attributed to two distinct causes—thrust developed during startup and environmental and oil conditions (see Figure 1).

thrust-bearing-pad-behavior

Figure 1. Behavior of thrust bearing pads based on thrust and environmental conditions (Article images and graphics courtesy of Hydro Inc.)

The significant finding from this data was the temperature rise associated with thrust. The pump could not achieve the temperatures measured prior to maintenance in its current condition. The total thrust bearing temperature includes the oil temperature and environmental conditions.

Based on comparisons with previous site data, both the thrust and oil cooling had altered. Analysis of the temperature data at the motor bearings, which were experiencing oil temperature increases of 10 to 15 C, further supported the conclusion. Continue reading

Hydro’s Perspective On The Global Aftermarket

Written by: Sarah Schroer
Publisher: Pump Engineer Magazine / May, 2014

 

Hydro is a global leader in the pump aftermarket repairs, upgrades and engineering solutions.

Pump companies typically fall into one of two categories: the original equipment manufacturer (OEM) that design, build, and sell pumps; and smaller, local machine repair shops. But Hydro offers the pump industry the best of both worlds. George Harris, one of the original founding engineers and current CEO, explains Hydro’s unique worldwide market position: “We have developed a unique niche where we have the engineering services, the testing capabilities, and the worldwide footprint that the large OEMs have, but we still maintain the exibility and the cost-effectiveness of the smaller companies.”

Harris also emphasizes that engineers are the heart of the company. Nick Dagres, the Vice President of Nuclear Operations in Chicago, notes that “We focus on aftermarket services and support. We implement engineering modifications to improve the performance of pumps that are out in the field.” By offering pump rebuilding, engineering, and upgrading at each service centre, Hydro can more effectively service the special needs and requirements of customers in each region. Staying close to the customer is one of the fundamental tenets of Hydro’s strategy and culture.

 

(Left) Hydro’s long list of services include welding-related repairs, such as performed on this 2 ½” Pacific RL IJ charging pump. (Right) A thorough quality inspection is carried out by Hydro’s detail oriented engineers.

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New Technology Solves Aftermarket Parts Problems

Written by: Dr. T. Ravisundar and Dibu Chowdhury, HydroAire, Inc,. and Heinz P. Bloch, P.E., Process Machinery Consulting
Publisher: Pumps & Systems / March, 2014

 

Industrial equipment users are often confronted with pump parts issues and must make choices. Handling these issues requires making experience-based decisions and prioritizing. How pump hydraulic and wear components in existing inventory are treated is an issue that merits consideration. Plant size, age, past purchasing, maintenance and storage-related practices are among the factors that affect a facility’s status with respect to operational readiness and downtime risk.

As these generally-known facts are applied on a pump component level, it is often determined that the specific pump components in the storehouse may not be the same as the components currently operating in a particular process centrifugal pump. Nor is it always the case that truly optimized components are presently installed. Therefore, the risk of experiencing unforeseen downtime can be reduced by having the right parts on hand. If the parts are truly optimized, installing them at the next opportunity will take the facility beyond being back in business—it will actually take the equipment owners to greater profitability.

To ensure that pumps will perform their intended functions, inventoried or stocked parts should be thoroughly inspected and corrected as needed prior to installation. Incoming inspection is practiced by best-of-class equipment owners and only verified-as-correct parts will be placed in the storehouse. This case study examines a real-life scenario and demonstrates essential precautions that can be taken when procuring pump hydraulic and wear components.

 

A Condensate Pump Repaired & Improved

During a planned outage, a nuclear power plant (NPP) sent a three-stage condensate pump to a highly experienced service center with hydraulic pump design engineers on staff. The NPP provided the hydraulic components, wear rings and bearings from its stock inventory for the pump rebuild project. The hydraulic pump design engineers at the service center performed a thorough inspection of both the disassembled rotor and the parts supplied by the NPP. A visual inspection quickly revealed that the geometry of the replacement impellers did not match the impellers that were removed from the disassembled pump (see Figure 1).

 

Figure 1. Cross-section of a three-stage pump created by an experienced pump repair facility for this three-stage pump. Note semi-open impellers in stages two and three.

 

 

Left: Impeller from disassembled pump
A) Leading edge of vane is straight.
B) Ring turn face to leading edge dist ~ 7/16 inch

Right: Spare impeller supplied from inventory
A) Leading edge of vane edge is curved.
B) Ring turn face to leading edge dist ~ 1inch

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Collaboration and Innovation Result in Efficient Outage

Written by: Paul Gray, Joe Alvey, and Jackson Simmons, Calvert Cliffs Nuclear Power Plant,
Brian Hegarty, Hydro East, Simon Daou, P.E., HydroAire

Publisher: Nuclear News / September, 2013

 

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

 

 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

Written by: Jeff Smith, Hydro Parts Solutions Inc., Dr. T. Ravisundar and Werner Barnard, HydroAire Inc.
Published: June, 2013

 

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.

 

Severely eroded suction bowl (Photo Courtesy of Hydro Inc.)

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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