Eliminating Water Column Separation and Limiting Backspin at a 12,000-Horsepower Pumping Plant

Otter, Paul; Hoisington, David; Raffel, David; ,

Eliminating Water Column Separation and Limiting Backspin at a 12,000-Horsepower Pumping Plant

by Paul Otter, CH2M Hill, Milwaukee, United States,
David Hoisington, CH2M Hill, Milwaukee, United States,
David Raffel, CH2M Hill, Milwaukee, United States,

Document Type: Proceeding Paper

Part of: Fundamentals and Advancements in Hydraulic Measurements and Experimentation

Abstract:

Milwaukee's Water Pollution Abatement Program includes a deep tunnel system which collects combined sewage and street runoff during storms for later treatment when capacity is available in the wastewater treatment plants. The Inline Pump Station contains three pumps, each driven by a 4,000-horsepower electric motor. The plant is capable of lifting 150 million gallons per day (mgd) (6.6 m³/s) 350 feet (107 m) from the tunnels to the ground surface treatment plants. Prior to system startup, while the pump station was being used to remove tunnel infiltration, water hammer became increasingly severe whenever a pump shut down. Two conflicting problems required solution before continuous pumping could begin. First, the severe water hammer had to be eliminated, and second, pump speed in the reverse direction after shutdown (backspin) had to be limited to 125 percent of the forward speed. A testing program was undertaken to measure the water hammer wave pressures and to quantify the effectiveness of the proposed solution. Very accurate measuring equipment was necessary because of the small time interval between events.

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