Pollution Engineering - October 2008 - (Page 52)

Positive REDUNDANCY and sales for the lift station manufacturer, “Our systems pump lots of water against friction losses, dynamic head and other factors, and that requires a sharp analysis to specify the right size generator.” trol; ambient temperature range; elevation above sea level; anticipated growth in the area served by the lift station; and pollution control requirements. tor sets need to be oversized to handle a motor’s higher starting current,” he said. “But over sizing can sometimes be avoided by specifying variable frequency drives or solid-state starters to reduce the inrush of current during starting.” Performance parameters The diesel-powered standby generator sets at the lift stations ranged from 20 to 200 kW. While some became part of permanent installations, others were adapted as portable, trailer-mounted units. The power output specification depended primarily on the size of the pump at each lift station, which ranged from 11 to 35 horsepower. At the Hunter Ridge lift station, twin pump motors require 39.6 kW for starting and 22.5 kW for running. All of the lift stations are required to run both pumps simultaneously, when necessary. Aside from pump motor horsepower and voltage, other critical performance parameters include starting current; motor efficiency rating; required auxiliary loads, such as generator set controls, lights, heaters and odor con- “ Leaving a programmable gap of several seconds between power sources allowed the back-EMF generated by the lift station’s pump motors to fully dissipate. Transferring power The lift stations included open-transition transfer switches, which provided breakbefore-make power transfer from the grid to the generator, and back again for both testing and power outages. Leaving a programmable gap of several seconds between power sources allowed the back-EMF generated by the lift station’s pump motors to fully dissipate, which is important to protect the generator set’s alternator. The time gap also allowed the generator set to get up to operating speed and stabilize its output voltage. The gap between power sources was programmed into the OTEC switch to accommodate the parameters of the motors and generator set in each specific lift station. From these parameters, Jim Stalnaker, sales manager with the power generator company’s Portland office, determined the engine, alternator and excitation system for each new lift station. “Some genera- ” 52 Pollution Engineering OCTOBER2008 PLE07081Tank.indd 1 9/8/08 10:14:51 AM 6/5/08 9:57:22 AM PLE10084NAWS.indd 1 http://www.nawatersystems.com/ http://www.tankconnection.com http://www.tankconnection.com http://www.liquidtanks.com http://www.nawatersystems.com/ http://www.nawatersystems.com http://www.tankconnection.com

Table of Contents Feed for the Digital Edition of Pollution Engineering - October 2008

Pollution Engineering - October 2008 Contents The Editor’s Desk EnviroNews PE Events Legal Lookout Green Connections Clearing the Air Water for People There’s a New Show in Town Catching Wind for Clean Water Taking the Pressure off Blower Selection Pulsed Plasma Positive Redundancy Product Focus: Municipal Water Treatment Product Focus: Monitoring Equipment PE Products Classified Marketplace Advertisers Index State Rules

Pollution Engineering - October 2008

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