Fertilizer Focus: Resolving Design Flaws in UAN Solution Pump

Heavy Wear of the Bushing Bore

A newly commissioned US fertilizer plant was experiencing recurring vibration problems with their vertical UAN Solution pump. The VSF vertically suspended pump was removed from service and sent to Hydro for a full inspection and investigation of the vibration source. When the pump was disassembled, it was evident that there were significant problems at the motor bearing and guide bushing locations. These design flaws that were affecting reliable operation of the pump.

Inspection of the motor thrust bearing revealed that the ball bearing cage had become unseated and was damaged. During Hydro’s analysis, it was determined that the motor thrust bearing was unsuitable for the service. The OEM chose a single row, angular contact bearing that could only handle thrust in one direction. During start-up, when the pump experienced an upthrust, the bearing became unseated. The unseated bearing was unable to function properly, even when the pump reached its normal operating thrust. This unrestrained upward motion of the shaft also caused damage to the mechanical seal faces.

Upgraded thrust bearing design

Another problem detected during the DCI was elliptical wear of the bearing bores. In this pump, the lineshaft couplings were located under the guide bushings, which is very atypical. Lineshaft couplings are areas where the greatest runout often occurs, resulting in a greater probability of contact and wear in this area. This problematic design was coupled with excessive tolerances on the columns, spiders, sole plate, and motor flange that affected centerline compatibility of the components.

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Lineshaft Coupling Design Change

The pump was upgraded to a new design that included a relocation of the lineshaft couplings, a new thrust bearing that could handle load in both directions, and an improvement of all component tolerances to minimize the possibility of component misalignment. Almost 70% of the pump was redesigned; this work was completed on an emergency schedule of only 2-3 weeks. Since reinstallation, the pump has operated successfully with reduced vibration.

State of the Art Parts: Double Suction Impeller

Hydro Parts Solutions recently provided a double suction impeller for a Gulf Coast refining and petrochemical site. As is standard with Hydro’s cast parts, this complex component was:

  • Scanned
  • Reverse engineered
  • Reviewed by Hydro’s engineering team
  • Cast
  • Final machined
  • Compared to the original model

The process for manufacturing the impeller was quoted at Hydro Parts Solutions’ standard delivery time of 6-8 weeks. The impeller was completed, inspected, and shipped to the customer within 6.5 weeks.

 

 

Reverse Engineering – An End to Obsolescence

A nuclear utility had a large circulating water pump with severe vibration issues that required refurbishment in an emergency time frame. Hydro’s Aston, PA service center, which has a 50-ton crane and a history of providing quality repair for nuclear non-safety related equipment, was chosen for this work. Despite the unique challenges in machining and maneuverability presented by large pumps, the DCI and refurbishment were performed in under 2 weeks.icon

This pump model is an obsolete design with very few existing installations. During the refurbishment process, Hydro’s reverse engineering team captured the data necessary to create a verified model of the pump components. Developing a reverse engineered model was a crucial step in establishing a reliable source to manufacture these large components. With the verified model and Hydro’s casting and machining capabilities, the plant can plan ahead to ensure all critical components are available for future refurbishments.

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Fully Equipped & On the Move

Hydro was called on to reverse engineer a large circulating water pump in the Caribbean to supply parts for refurbishment. The lead times for receiving parts from the original equipment manufacturer (OEM) were excessive. More concerning, the suction bell provided by the OEM had failed during service. All internal ribs were lost, and the bearing holder was found loose within the assembly.

When Hydro reviewed the design of the suction bell, it was clear that low manufacturing cost was prioritized over reliability. Instead of providing a cast component, the suction bell was fabricated and had an excessively thin wall thickness.

Hydro reverse engineered the suction bell and created a model for a cast component, establishing the rib design and bearing holder location based on design experience. Exterior ribs were added to strengthen the bell and the wall thickness at the suction bell skirt was increased from 3/8” to 2”. The part was scanned on-site within 1 day, with the engineering analysis, modified casting design, and quote for manufacture being
completed within about 3 weeks.

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Optimum Flow – Expert Solutions When It’s Critical

A major county in California found itself in a crisis when its irrigation pumps could not produce the required performance, cutting off critical water supply to the reservoirs and aqueducts. These pumps suffered from high vibration and repeated failures characterized by extreme wear to the propellers, shafts, and bearings.

The OEM had extended their abilities as far as they could but were unable to resolve the problems. Hydro’s engineering team was called on to provide a failure analysis and design an effective solution. Hydro found that deflection induced by high radial forces, excitation of the rotor critical speed at running speed, and faulty protection from sediment all contributed to the failures.

Evans Hydro redesigned the bearing span to counteract the deflection and critical speed issues. The pump-out vanes were also redesigned to provide better lubricating flow to the guide bearings. Finally, the protection rings were redesigned to keep sediment from the propeller and provide better overall dynamic balance.

The solution provided by Hydro significantly increased the life of the pump. Not only were the changes effective, but they were executed efficiently. The modifications were completed in an expedited time frame, allowing the county to resume reliable water service to the agricultural industry that depends on it.

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