Emergency Nuclear Pump Rebuild

Faisal Salman and Nick Dagres of Hydro, Inc report how performing new design modifications on two critical safety-related charging pumps have extended their lifespan and reduced maintenance.

Written by: Faisal Salman & Nick Dagres
Published by: World Pumps

Certified Test Lab

Setting up the pump at Hydro’s Hydraulic Institute Certified Test Lab.

A Western European nuclear power plant was having difficulty meeting the necessary hydraulic performance at runout for two centrifugal charging pumps. The system needed 30 ft of Net Positive Suction Head required (NPSHr).

The pumps are safety-related pumps, which pump bore-rated water (water mixed with boric acid) into the reactor to kill nuclear fission. What water is to fire, bore-rated water is to nuclear fission. Bore-rated water kills nuclear reaction.

The two pumps are each about 15 ins in diameter and about 100 ins in length. They were shipped from the Western European site to Hydro, Inc.’s Chicago, IL facility to conduct analysis, redesign, manufacturing, and testing.

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Quality Nuclear Performance Testing in Urgent Conditions

A 5-day emergency testing turnaround for a nuclear pump proved no problem for this world-class testing facility.

Written by: Nick Dagres & Faisal Salman
Published by: Nuclear Plant Journal

When a vertical safety-related residual heat-removal pump failed its required surveillance performance test at a nuclear power plant, it created the need for emergency hydraulic performance and vibration testing. The plant required the pump back in operation within one week, to prevent shutdowns that could cost the facility up to $1 million per day.

The plant contacted Chicago based Hydro, Inc., which has Hydraulic Institute (HI) Pump Test Lab Approval (PTLA) – certified testing facilities and the ability to perform crucial testing on an urgent basis.

Background
During a routine check by the regulator, a safety-related heat removal pump failed its required in-house surveillance pump performance test. With a safe shutdown of the unit, the plant entered an LCO (Limited Conditions of Operation) period. The power station shut down the unit but wanted to avoid a full shutdown of the facility. This created an emergency situation for the plant.

According to the regulator’s strict standards, if performance requirements are not fulfilled immediately, the plant can be shut down completely. The LCO allows the plant to continue to operate as long as the problem is being resolved in a limited time frame. In this case, the time frame was seven days. To allow for shipping to and from the facility, Hydro had only five of those days to complete the project. The plant was concerned that the repair time might exceed the LCO. Other similar pumps remained in operation performing the same function, however the unit was shut down because there were no spare pump store place it while testing was being
performed. The original equipment manufacturer could not schedule the required tests in the abbreviated time span; therefore the Chicago service company was commissioned. Under normal conditions the scope of work would generally take about six to eight weeks to complete.

Pump as received

Pump as received

Identifying the Problem
In such cases, the regulator requires that a third party inspect the equipment to discover whether the issues were with the instrumentation or with the pump itself. As a result, immediate testing was required to determine whether the pump was functional.

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Analysis & Rerating Solve Pipeline’s Acoustic Resonance Problem

The phenomenon occurs when a system experiences extreme vibration caused by excessive pump pressure and pulsation.

Written by: Greg Matteson & Jeff Johnson
Published by: Pumps & Systems

A North American natural gas liquids pipeline company was experiencing an acoustic resonance issue that cost up to $35,000 a month in maintenance and repair. A six-week project resulted in rerating three American Petroleum Institute (API) designation between-bearing (BB3) horizontal multistage split-case mainline pumps and performing extensive and specific vibration analyses to identify the problem. The project involved designing and manufacturing new impellers using exclusive milled vane technology, conducting API hydraulic performance tests, and returning the pumps into service.

This midcontinent pipeline gathers, processes, stores and transports natural gas—in this case, propane. Because of its geographic location, extreme temperatures and conditions are a factor in the selection of major equipment and components. The pumps operate at 2,917 gallons per minute with 2,926 feet at 1,500 horsepower and 3,560 revolutions per minute (rpm).

The Problem

The pipeline company was experiencing an acoustic resonance vibration problem at the pump crossover, causing major maintenance and repair issues. Acoustic resonance occurs when a system experiences extreme vibration due to excessive pump pressure and pulsation, with frequencies loud enough for humans to hear. This can happen with the use of variable speed drives.

The pulsations are caused by a non-uniform flow from turbulence, sudden change of flow structure, direction or cross-section.

The acoustic resonance had existed since the pumps were installed more than five years ago. Rather than repairing or replacing them, the company performed continuous unscheduled maintenance that cost as much as $35,000 in a single month.

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Using Latest Technology to Refurbish a 50-year-old Pump Element

Power pump performance improved with redesign of the first-stage, double-suction impeller and twin volute.

Written by: Dave Allard & Dr. Gary Dyson
Published by: Pumps & Systems

In the aftermarket business, part replication is not enough. Precision engineering combined with the latest technology are essential for manufacturing high-quality parts. A main boiler feed pump at a Midwestern United States power plant was built in 1967 using sand casting and wooden patterns, now considered outdated technology. Even though the pumps received refurbishment every six to eight years, the pumps continued to have low performance as well as vibration issues.

Using all its resources—including casting simulations, 3-D models, up-to-date foundry casting techniques and considerable engineering data—an engineering and repair services company fully manufactured a complete element, performed sophisticated testing in the Pumps Test Lab Approved Program (PTLA) certified test lab, and returned the pump to operation within just 12 weeks.

This project involved the manufacture of a complete first stage twin volute and a description of the latent defects.

The pump suffered from ongoing vibration issues which were caused by pressure pulsations at vane frequency. To improve the vibration levels, hydraulic analysis and redesign were required to develop a new, improved design.

This project has been divided into two articles. The first is the manufacturing of the twin volute and the second is the design of a new impeller.

Image 1. A received bundle showing failure in the twin volute stage piece. The aftermarket company received the internal element and casing (pump bundle, or element) of the pump. (Images and graphics courtesy of Hydro, Inc.)

Image 1. A received bundle showing failure in the twin volute stage piece. The aftermarket company received the internal element and casing (pump bundle, or element) of the pump. (Images and graphics courtesy of Hydro, Inc.)

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Engineering is at the Heart of Hydro Inc.’s Aftermarket Services

Hydro Inc. has a strong engineering capability and an expansive global reach in the pump industry, especially in aftermarket services. Pump Engineer had the pleasure of speaking with George Harris, Chief Executive Officer and Founder of Hydro Inc., where he discussed the company’s recent research initiatives, reliability support for customers, customized designs and the significance of upgrades and health audits.

Written by: Deirdre Morgan
Publisher: Pump Engineer / December 2016

“We were very fortunate that early in the company’s development we had the good fortune to work closely with Dr. Elemer Makay, a foremost consultant to the power generation industry and a specialist in troubleshooting multi-stage, high energy pumps”, states Harris. “Engineering combined with meticulous observation and analysis in the field were key to his troubleshooting process. As a result of his training over a twenty year period, engineering became the focus and strength of Hydro Inc.’s aftermarket services”.

According to Hydraulic Institute statistics, 85% of the critical pumps in industries, such as power, refineries and pipelines, are custom designed for the specific application intended. In order to properly rebuild, upgrade or troubleshoot these installations requires a solid aftermarket engineering capability and experience. Not only must the engineer understand pump fundamentals, but also the application and system in which the pump is being used, as well as the changes that may have occurred in plant operating conditions since the pump was originally installed.

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