Fifteenth Annual Vail Operator Training Seminar Understanding Centrifugal Blower Operation in Wastewater Aeration and Dissolved Oxygen Control Presented by: Nicholas Radley Project Engineer N.E. Controls, LLC

Aeration Control Overview N.E. Controls History Blower Basics Aeration Control Systems Aeration Control Equipment

N.E. Controls, LLC Lamson / Hoffman Empire in Syracuse, NY Gardner-Denver buyout Peachtree City, Georgia or bust Three partners formed N.E. Controls in 1997 Almost 60 combined years of experience in the blower business. Now our business of 10 employees build various controls for use in Water / Wastewater treatment and other industries.

Centrifugal Blower Basics Flow based machine not pressure based More similar to a fan than a compressor Excels at moving large volumes or air but not overcoming large pressure gradients

How a Blower Works First-stage impeller draws air through inlet First-stage air is forced outward, away from shaft and casting design directs air into second-stage impeller Flow pattern continues through machine until air is exhausted though outlet.

Blower Customization Output pressure increases as more stages are added Blower pressure and flow characteristics can be tuned with different combinations of stages, impeller profiles and power ratings

Efficient Operation of Blowers Throttling:  VFD (Speeding)  Discharge Valve  Blowoff Valve  Inlet Valve Inlet throttling is the most cost effective way to throttle a centrifugal blower

The Blower Performance Curve Top curve is Amps vs. Flow Bottom curve is Pressure vs. Flow Blower always runs at system resistance pressure Throttling shifts curve to lower values

Centrifugal Blowers for Aeration Control System Options Manual Control Header Pressure Control Air Flow Control Dissolved Oxygen Control

Manual Control “Looser” Control Update time in hours to days range Typically uses excessive energy Power savings vs. automated system Man-hour costs

Header Pressure Control Common control scheme used for positive displacement blower systems Centrifugals always run at system resistance pressure Does not transfer very successfully to centrifugal blower systems

Air Flow Control For effective control need flowmeter on every drop Works well with centrifugal systems Expensive Ultimately need DO measurements for permit info anyway

DO Control Direct control of desired process variable Modern DO sensors are more user friendly Update times are slower than flow or pressure systems

Aeration Automation Concerns Blower Sizing Requirements Sensors Required Automated Valves

Blower Sizing Blower Frame Size / Configuration Blower Turndown Blower Overlap Can different sized blowers run together? Pressure requirements

Sensors Dependent on control scheme Process Sensors  Pressure, Flow, DO Blower Protection and Monitoring  Vibration, Flow, Amps, Temperature, Hours, Pressure

Automated Valves Are there existing valves or actuators? Open/Close or 4-20 mA actuator Valves sized correctly? Provides more precise and frequent positioning than manual control

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