Monday, April 2, 2012
GENESEE COUNTY WASTE WATER DRAIN COMMISSION: BY GARY MALEY - DETROIT PUMP & MFG. Co.
Michigan county selects a Cornell pump for its new pump station.
Genesee County, where Flint, Michigan is located, had an issue with their wastewater Pump Station No 1. Employing a vertical line shaft and dry pit pump design, the station was becoming increasingly expensive to maintain and operate. Adding to maintenance issues were the pump station’s age and location—it had been operating for more than 30 years within a floodplain. The station was flooding several times a year, requiring costly repairs and loss of use of the station.
In 2010, the Genesse County Commissioner approval a replacement project of the old station. The county awarded consulting engineering firm Hubble, Roth, and Clark (HRC), from Bloomfield Hills, Michigan the contract to design the new station. Design specifications called for the new pump station to handle a peak flow capacity of 60 MGD; in order to reduce or eliminate station flooding, improve efficiency, and assure reliable operation.
To meet those objectives, HRC determined the design features of the project needed to include a minimum of 30” suction and 24” discharge, that motor horsepower could not exceed 350HP, that the station be equipped with a variable frequency drive system, and that the system have the ability to function should the new station flood.
The consultant review study included evaluation of submersible type, non-clog sewage pumps versus vertical non-clog sewage pumps with immersible motors. Whichever pump was selected needed to have a capacity of 20 MGD at approximately 75’ Total Dynamic Head (TDH). The consultants considered pumps from Flygt, KSB, and Cornell that met the criteria.
After weighing how best to meet the design objectives, HRC recommended that the project proceed with the immersible pump and motor design. That configuration was promoted based on evaluations of efficiencies achieved by the pumps and comparisons of associated costs of cooling systems for the motors. The submersible design was not chosen because of cooling requirements inherent in the design; it required recirculating pump fluid with a water jacket cleanout/ flushing ports, the need to build to allow possible future conversion to an external cooling system, and the necessity to install extensive monitoring equipment for motor stator temperature measurement, seal failure leak detection, and bearing temperature levels.
Today, the new Genesee Pump Station No. 1 is fully functional, utilizing four (4) Cornell Immersible Pump Model 20NHF-VC20 operating at 720 RPM, 350 Hp, with Continental Immersible Motors. The station was put the test in the first couple months of operation—heavy spring rains forced the station to maximum capacity. It performed above design standards, reaching and maintaining 76 MGD—26 percent above design requirements.
Cornell pumps were a logical choice for this important public works application. They greatly improved on the previous “line shaft” design of the original Fairbanks-Morse pumps. As a distributor to Genesse County, we were happy to provide the Cornell Immersible Motor and Bearing Frame for the application. We believe it to be the most efficient and maintenance friendly choice!