R2017-24 Bodine Electric High Service Pump Motor Repair

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Public Works DATE: 2/13/2017 MEMO: 2017-11 TO: Honorable Mayor Moore Wolfe and City Council Members FROM: Tim Gleason, City Manager Richard G. Marley, Public Works Director SUBJECT: South Water Treatment Plant High Service Pump Motor Repair SUMMARY RECOMMENDATION: City Council adopt the attached Resolution accepting the quote of Bodine Electric of Decatur for South Water Treatment Plant High Service Pump Motor Repair in the amount of$34,928.76. BACKGROUND: The South Water Treatment Plant has five large General Electric high service pumps powered by electric motors that pressurize the city's water distribution system. All the large pumps were installed when the South Water Treatment Plan(SWTP)was completed 29 years ago. The motor which powers the pump used most often throughout the year recently failed and needs to be repaired or replaced with a new motor. The five large motors have different horsepower ratings and drive differently sized pumps. The motors and pumps are cycled on and off in various combinations to match water consumption that varies throughout the day.None of the pumps are equipped with variable frequency drive which enables operators to adjust the speed of the electric motor and vary the volume of water being pumped. The motor that failed drives the pump that delivers a volume of water that best matches water consumption, and as a result is used most often to supply water. After this motor failed, water plant operators were able to continue pressurizing the system by cycling other larger and smaller motors to supply water. Cycling other pumps has four main drawbacks: 1. Every time a large pump motor is started or stopped, a pressure wave is created in the water mains. The City's water mains are old and fragile as demonstrated by the frequency of water main breaks. The longer this problem remains unsolved, the higher the possibility of water main breaks. 2. Starting a large electric induction motor under a full load places enormous stress on the electrical and mechanical components inside the motor itself because the motor will accelerate from full stop to full operating speed in only seconds. 3. As water consumption begins to increase in spring reaching its peak in the summer, the frequency of starting-stopping cycle operations will tend to increase, worsening problems described above. 4. With one of the five electric motors and pumps out of service, redundancy in the water system is reduced, leading to increased chance of other equipment failure. It is recommended that the motor be repaired instead of being replaced for the following reasons: 1. The quoted repair cost is $34,928.76 compared to an estimate of$65,000 for a new motor. The new motor price quote does not include possibility of having to modify the motor mount footprint to align with the existing mount in the water plant. 2. The warranty is the same for both options (one year parts and labor). 3. It is estimated that the efficiency(electricity used)by the repaired motor is about the same as a new motor. The existing electric motors are slightly above 70%energy efficient,which is remarkably good.