Poor water quality can be a factor in degrading pump reliability and MTBR.
by Ken Babusiak & Bob Jennings
March 4, 2019

A major steel plant on the East Coast had been experiencing catastrophic failures with their five- stage descaling pumps for more than four years. The plant operated using three multistage axially split (BB3) pumps with two spares.

All five of the pumps had a mean time between repair (MTBR) of two years.

The plant water quality was considered to be less than ideal, and the entrained abrasives were a factor contributing to the repeated failures.

damaged impellerImage 1. Damaged impeller showcasing severe corrosion. (Images courtesy of Hydro Inc.)

In an effort to improve pump operation, the client reached out to both the OEM and several aftermarket repair shops over the past five years with hopes for a more permanent solution.

Maintenance records indicated that one pump was repaired several years ago by one global aftermarket pump service provider and it had provided the longest run time, operating more than four years without failure.

Based on the extended run time of the pump, the client reached out to the same aftermarket pump service provider to assess the situation and provide the repairs required to increase the running time for all pumps in operation.

newly installed impellerImage 2. Newly installed impeller and components after advanced engineering upgrades.

The Challenges & Issues

Poor water quality can lead to a number of pump reliability issues. When pumping fluids with abrasive material, pumps experience erosion and corrosion, and the effects can rapidly degrade both the casings and critical inner elements.

While erosion and corrosion alone are not always a difficult problem to solve, it is important to have a firm understanding of the relationship between various types of erosion and corrosion and the metallurgy used in designing the pumps. An analysis provided results that showcased excessive clearances and inconsistencies with component fits that also contributed to pump performance degradation outside the abrasion.

Analysis & Action

The pump casings and rotating components were completely cleaned, inspected and digitally mapped using current laser scanning technology. The hydraulic design engineers then analyzed the impeller and volute geometry. The team recommended manufacturing new impellers, which would increase pump performance while providing higher efficiency and greater hydraulic stability.

vibration dataImage 3. Real-time wireless condition monitoring sensors may be used to gather vibration data and analytics.

Impact & Results

In order to increase the MTBR of the pumps at the plant, the aftermarket pump service provider also recommended several engineered upgrades including new impellers, which were manufactured using advanced mold technology. This produces components that specifically address surface finish and dimensional consistency.

The splitter on the bushings was also upgraded to provide a better interstage water flow, reducing internal hydraulic turbulence and the vibration levels of the pump. With the aftermarket engineers on the project, the client was provided with a field service team to install and remove all of the pumps.

A wireless condition monitoring system to support the plant’s pumps was also established. Two pumps were actively in service, monitored by 10 magnetic wireless sensors measuring vibrations up to 20,000 hertz (Hz) with automated alerts and predictive reporting protocols.

installed impellerImage 4. The newly installed impeller and components.

Wireless remote monitoring allows operators and engineers to see real-time data and to make educated decisions regarding their assets.

A wireless data collection system assists users to identify issues before they escalate.

In contrast, it is possible that a route-based data acquisition strategy may miss these events depending on the frequency of the route.

installed impellerImage 5. The damaged impeller and components.

Conclusion

The analysis and customized engineered solutions by the aftermarket pump service provider yielded positive results, as the pumps are now operating with significantly improved MTBR.

Originally, the plant was sending repairs to local shops, which provided adequate service but could not identify and correct the root cause of the continued issues (component incompatibility) that required forensic engineering analysis (FEA) to understand.

As a result of the higher repair standards and the means to provide customized upgrades, along with the ability to provide engineering analysis to identify the root cause of the shortened MTBR, the aftermarket pump service provider has become the singular source for all repairs and required field service for this project.

Poor water quality and other corrosive material can lead to heavy erosion, cavitation and hydraulic turbulence, which can damage a pump. Understanding how a pump functions in correlation to the material it is pumping can offer great insight into the type of damage and the best customized, engineered upgrades available.