Finding flaws with Forensic Analysis

A fertilizer plant in the Gulf of Mexico experienced a suction cavity high pressure ceiling leakage in one of their BB5 boiler feed pumps. By utilizing a forensic analysis, Hydro discovered a simple shortcut in the manufacturing process was costing thousands of dollars in repairs and great inconvenience.

Written by: Pete Erickson and  Todd Soignet
Published by: World Pumps

A BB5 barrel pump at a fertilizer plant along the Gulf of Mexico experienced reduced capacity due to suction cavity high pressure sealing leakage. This was not the first time their boiler feed pumps had experienced a loss of capacity. The pumps were only about a year and a half old and were part of a major expansion project at the plant.

Due to high lead times, the plant decided not to continue repairs, but instead do a simple swap out, when a Hydro service center was recommended by the client’s sister plant as a credible supplier who had the technical and engineering expertise needed to rebuild pumps to the highest quality standards.

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Beware the Cheap Fix: You May Get What You Pay For

Fossil plant required an emergency rebuild when poor quality repair caused a holiday shutdown. 

Written by: Dr. Gary Dyson & Mohamed Mohamed
Published by: Pumps & Systems

The consequences of poor quality repairs can result in premature failure, unplanned outages and higher repair costs because follow up after the initial attempt is considered an emergency repair. That was the situation when a major fossil plant experienced an emergency failure of a six-stage, boiler feed pump element. It was a quiet holiday night when the pump had to be pulled due to lack of flow, causing a plant shutdown. Unfortunately, when the plant tried to set the spare element up on bearings, employees were unable to turn the rotor. In this case, the emergency occurred when the repaired spare element had to be used immediately after initial failure. Thus, the problems with the previous repairs were uncovered.

Because it was the holiday season, the plant’s usual service provider could not respond in the required time. Another Hydro was called in to assess the problem, engineer a solution and save the plant thousands of dollars in downtime.

Field service was mobilized to provide labor in two 24-hour shifts.

Worthington element

Image 1. Worthington element set on precision v-blocks, checking vertical and horizontal clearances at the suction end and discharge end. These checks are used to see if element is concentric.

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Seal replacement reveals causes of excessive vibration

During a mechanical seal replacement of a major gas plant, a reliability engineer identified that the pump was operating below Minimum Continuous Stable Flow. To resolve this issue, one company engineered modifications to the casing and impeller.

Written by: Angelo Miller (Hydro, Inc.) & Eddie Janson (John Crane)
Published by: World Pumps

Adjusting case piping

Figure 1: Hydro mechanics adjusting the case piping.

Vibration commonly causes pumps to operate at low flow and reliability plays a key role in the cost effectiveness of systems. The pump in question was an additive booster pump. The seal manufacturer contacted Hydro to collaborate. Hydro’s field technicians identified that there was excessive vibration which increased wear on the mechanical seal.

Hydro plotted the current conditions on the pump curve and determined that the pump was operating below MCSF for which performance factors such as efficiency, rotor dynamic stability, bearing and mechanical seal life become negatively affected, yielding a drastically reduced Mean Time Between Repairs/Failures (MTBR/F). The company performed an OH2 power-end upgrade and a pump hydraulic rerate.

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Pump Renovation Restores Balance

Vibration issues with a two-stage pump forced a major steel manufacturer to remove the pump from service. Due to incorrect weights welded on an impeller, a steel manufacturer called upon Hydro to repair and balance a two-stage pump.

Written by: Ken Babusiak (Hydro, Inc.)
Published by: World Pumps

The pump was experiencing the vibration during the spring and summer months of 2016. The steel company sent the pump to HydroAire’s Chicago, IL facility in September of that year. HydroAire was able to determine the cause of the vibration and created a solution that got the pump back in operating condition. The pump was installed and back in service by February, 2017.

The initial testing and analysis deter-mined that the impeller had large weights welded onto it. The steel company was concerned for many reasons, especially because the staff knew that using weights was not the correct way to balance an impeller. This caused the steel manufacturer to question the manner in which the pump had previously been repaired.

Weights added to impellers

Adding weights to impellers is generally not standard practice.

Where not to position the weights.

Where not to position the weights.

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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. 

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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