Title
Resolution to Approve the Purchase of Two Allen Bradley, Power Flex 700, Variable Frequency Drives from McNaughton-McKay Electric Co. for Effluent Pump Motors at the Wastewater Treatment Plant ($46,080.00)
Memorandum
Your approval is requested to authorize a purchase order with McNaughton-McKay Electric Company for the acquisition of two variable frequency drives (VFDs) to replace two failing obsolete VFDs on effluent pump motors at the Wastewater Treatment Plant (WWTP) in the amount of $46,080.00.
These machines were installed nearly 30 years ago and have exceeded their useful life. Two of four old VFDs were replaced last year. Replacing the last two VFDs will complete the renovation of all the effluent pump motor VFDs.
VFDs are used to improve energy efficiency and maximize operational control of alternating current motors. The WWTP uses Allen Bradley, 1336 Classic, VFDs to control four of six 150 H.P. effluent pump motors in the plant’s water reclamation tertiary treatment process. Failure of a VFD at this stage in the process would be detrimental to the control of effluent flow to the sand filters by increasing the frequency of filter backwashing to keep the filter free of solids. Without VFD control, flow through the ultra-violet disinfection system would not vary proportionally to required disinfection demand causing higher operational costs. Plant energy utilization would also be adversely impacted by such a failure because these large motors draw correspondingly large currents at each startup.
Over the past five years the VFDs have failed several times for reasons associated with the electronic circuit boards and power transistors. The Allen Bradley, 1336 Classic, VFD is listed by the manufacturer as a discontinued and obsolete product. Since the manufacture of the Allen Bradley, 1336 Classic, VFDs have been discontinued, the production of circuit boards for the drive has ceased. No new circuit boards are available for immediate replacement. ...
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