Atlantic City (NJ) Sewerage Company (ACSC), a private utility with 7,500 connections in and around the “Boardwalk” casino district, keeps a keen eye trained on operating costs. Its focus until recently was on the excessive energy and maintenance expenses for three 300-hp long-shaft pumps at the Baltic Avenue Pump Station. The facility’s pumps were sized to handle the expected growth of the area’s casino industry. When anticipated development fizzled after the initial round of gaming and lodging facilities was built, ACSC was left with grossly oversized pumps that operated inefficiently and were prone to cavitation, which damaged the impellers.
Scope
The Baltic Avenue Pump Station was built with two levels: The office, MCC and motor room are at Elevation 10, while the lower level housing the pump room extends down to Elevation -16. The cavernous space inside the building presented a loud, often uncomfortably hot work environment.
A feasibility study indicated that significant changes to the pumping equipment were required, and the engineering firm suggested changing to submersible pumps in a dry pit configuration. These units would run quieter, use less energy and generate less heat, and their variable frequency drives (VFD) would allow them to operate more efficiently and consume less energy. Equally importantly, the utility would gain pumps that are immune to flooding, which was not uncommon given the powerful storms that hit Atlantic City off the Atlantic Ocean.
Solution
After a competitive bid process, ACSC selected Flygt units over those of two other pump manufacturers. ACSC replaced a trio of 300-hp long-shaft sewage pumps in the Baltic Avenue Pump Station with more efficient, clog-resistant Flygt dry pit submersibles manufactured by Xylem.
The first installation included a 135-hp pump sized to deliver 9,600 gpm at 36 TDH, followed by two 200-hp units that deliver 13,500 gpm at 40 TDH. All included VFDs that balance the operating pump speed with the inflow as measured by the depth held in the wet well. The larger pumps allow ACSC to stay on a single pump without cycling the lag pumps.
The sizing and engineering features of the Flygt pumps brought the station back into operational balance with the present flows. “Compared to the old long-shaft pumps, the Flygt pumps are saving 10 to 30 percent in energy cost and require minimal maintenance,” said Walter Miller, ASCS vice president of operations.
Result
The Flygt pumps have reduced overall operating costs and improved the bottom line for the company. They are more appropriately sized for their mission, and they require inherently less maintenance than the conventional long-shaft pumps they replaced—there are no shafts, packing glands, greasing of universal joints, pinion or steady bearings. Workers are pleased with the noise reduction; now they can have conversations at normal volumes.
Performing the same mission at half the horsepower of the 300-hp predecessor pumps, the Flygt pumps have delivered a 10 to 30 percent reduction in energy costs for ACSC, compared to the previous pumps.
“For us, the Flygt pumps have been the answer and everybody here loves them,” said Miller.
