VFDs maintain constant water pressure, eliminate water hammer

Problem

To handle growing water demands, the City of Cottonwood in the arid central highlands of Arizona devised a strategic water management plan that included creating a modern municipal water system with monitoring, control and pumping technology. The unusually high well-to-customer ratio presented piping and pumping challenges in accommodating more than 28 wells. Previously a 20 psi pressure change constantly stressed the pipe, creating leaks and water hammer on more than 100 miles of pipe.

Solution

Instead of turning pumps on and off, causing the 20 psi differential, the city converted nine sites from a fixed-speed hydropneumatic system into a duplex variable-speed, constant-pressure system using Danfoss VLT AQUA variable-frequency drives (VFDs). Using only the built-in Smart Logic Controller (SLC), the drives were programmed to operate in a lead, lag and duplexing sequence. When the lead pump reaches maximum speed, the lag pump starts, maintaining pressure within 2 to 3 psi.

Result

With the constant-pressure design, the average pipe pressure stays in a 60 to 65 psi range. One or more pumps are online at all times to keep the system pressurized, cutting down on leaks by reducing pipe fatigue and system damage. The design stabilized pipe pressure and nearly eliminated water hammer. Water main leakage decreased substantially, which means less time spent digging up and repaving roads to make repairs. 800/432-6367; www.danfossdrives.com.

Water district upgrades to advanced metering analytics system

Problem

When the Bethpage (N.Y.) Water District began improving its metering system three years ago, its main motivations were to improve efficiency and customer service with more advanced technology and gain more visibility into operations.

Solution

The district replaced all of its 9,300 endpoints with Badger Meter products and installed the company’s ORION advanced metering analytics system and ReadCenter Analytics Pro software. The system uses 5/8-inch Recordall Disc Series meters and 1-, 1 1/2- and 2-inch E-Series ultrasonic stainless steel meters with high-resolution encoders, as well as Badger Meter compound, turbine and fire service meters. Other components include gateways, and Trimble Ranger hand-held units with ORION transceivers to confirm endpoint installations.

Result

The district can now detect leaks more quickly and easily. The system’s two-way functionality streamlines and automates final billing and allows it to be handled remotely. The district captures more revenue, as hourly data can be used to detect when meters are under-registering and when accounts become inactive. Estimated payback on the investment is five years. 800/876-3837; www.badgermeter.com.