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Council approves $129,500 repair for hydro unit gearbox after staff details recurring failures
Summary
City staff told the council the hydropower unit’s speed-increasing gearbox requires frequent repairs; the council approved a $129,500 requisition to National Gear Repairing Corporation to repair unit 4.
Mount Pleasant city staff recommended and the council approved a $129,500 requisition to National Gear Repairing Corporation to repair the speed-increasing gearbox on hydro unit 4.
A city maintenance staff member told the council the gearbox assembly — a speed increaser that takes roughly a 400 RPM input and raises it to about 1,200 RPM to drive the generator — has required major work roughly every three years and sprays oil when seals fail. The staff member described coupling weight and repeated bearing failures as likely causes and said the city has spent several hundred thousand dollars over recent years on recurring repairs; he estimated the city saved roughly $800,000 over a four-year span through other efficiencies but still has put about $325,000 toward repeated work on the speed increaser.
The staff member described a possible technical solution: replacing the existing ruplex-style couplings and bearings with heavier-duty components (the staff referenced German-manufactured bearings and a so-called flux coupling option) and improving the gearbox cooling circuit. Staff emphasized that any modification would require engineering sign-off and that vendor-supplied engineering would be used to reduce risk. The vendor quoted a warranty; staff said they expect at least a three-year warranty on the work as quoted.
Council members asked about warranty length, engineering review and lead times. Staff said the vendor could provide the part quickly if the requisition was approved and that the city would still need to address instrumentation, alignment and connection work and to confirm an engineer to sign off on modifications.
The council approved the requisition. Staff listed follow-up tasks including providing the warranty in writing and coordinating engineering review and installation scheduling.
The transcript records technical descriptions and a staff estimate of prior expenditures; the council’s motion to approve the requisition was followed by an affirmative roll call in the meeting record.
