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. 

This project has been divided into two articles. The first, published in the June 2017 Pumps & Systems; the second, published in September 2017 Pumps & Systems.

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pump at a Midwestern United States power plant was built in 1967 using sand casting and wooden patterns, now considered outdated technology.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—Hydro 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.

Twin volute stage piece

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

The first-stage twin volute is a complicated casting, which failed during operation as a result of poor design.

Hydro re-engineered the casting by using sophisticated engineering and 3-D modeling, along with simulation software and 3-D sand printing.

In addition, Hydro identified the opportunity to improve the performance of the pump by redesigning the first-stage double-suction impeller. To improve vane passing frequency, the first-stage double suction impeller was redesigned with staggered and split vanes.

Hydro’s aftermarket services capability provided a completely new replacement element for this high-energy boiler feed pump and also redesigned the castings to eliminate the original latent defect in the casting design.

Hydro provided sophisticated hydraulic engineering improvements to increase the mean time between repairs (MTBR) of the newly manufactured element.

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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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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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How Root-Cause Analysis Solved a Vertical Turbine Pump Failure

A comprehensive approach to reverse engineering helped to establish the differences between the stainless steel and original bronze impellers.

Written by:  Hydro, Inc.
Publisher: Pumps & Systems / March 2016

 

When a severe pump failure involving one of three installed circulating water makeup pumps happened, facility personnel grew concerned about the root cause. The subject pump failed just 40 days after its commissioning.
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Image 1. A crack in the discharge head flange that involved fatigue failure of the weld of a pump.

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Image 2 (right). The pump’s impeller wear ring landing shows heavy scoring.

The equipment in question consisted of three-stage vertical turbine pumps running either in standalone or in parallel operation as required. The failure manifested itself through high vibration and caused severe scoring of the pump shaft and wear ring landings, leading to fatigue failure of the weld on the discharge head flange (see Images 1 and 2). The commissioned pump was refurbished and rebuilt by another company’s service center with spare impellers supplied by an original equipment manufacturer. No changes to the geometry had reportedly been made, although the impeller material had been upgraded from bronze to stainless steel.

The plant initiated its internal root-cause analysis process, and the failed pump required emergency repair. The station sought a company to conduct the repair, and the firm reviewed the customer-supplied documents and background providing the possible causes of the failure. Continue reading