Ethernet Keeps Water Flowing

The Waterford Township Water Department keeps the water supply up-to-date and flowing with the help of Ethernet-connected programmable automation controllers.

Since 1996, the Waterford Township Department of Public Works (DPW) has used Opto 22 hardware and software in its water treatment plants, sewer pumping stations, and other facilities.

Serving a community of more than 74,000 people just northwest of Detroit, the Waterford DPW has looked to Opto 22, based in Temecula, Calif., to provide the automation and control systems needed to pump and treat water from 15 wells and 10 water treatment plants into a 350 mile distribution system and 62 sewer pumping stations. The water plants are designed to remove iron and manganese (both secondary contaminants) from the water, and to inject chlorine for disinfection and orthophosphate for corrosion control.

NO BLACK BOX

The DPW is using the Opto 22 Snap PAC System to monitor and control it’s newest water treatment facility, which performs a biological iron removal process via pressure filters.

The DPW chose to install Opto 22 Snap PAC controls instead of using the “black box”-type control system typically supplied by the filter manufacturers. The DPW is able to create any type of control program it wishes, resulting in a finely tuned system. Snap PACs, and the accompanying PAC control programming software, provide the DPW with the flexibilty to design using flowcharts, which are much easier for everyone involved to use and understand.

The Snap PAC system also proves invaluable for the DPW because of the very high number of input/output (I/O) points involved in their applications. Many existing sewer pumping stations and treatment plants still use Opto 22 mistic I/O systems, which feature mostly single-channel modules, but the higher density Snap PAC line is now preferred because it boasts 4-channel (and even higher density 32-channel) analog I/O modules that can be used to take chlorine, pH, and other readings from the treated water. The DPW understands that higher density modules save cabinet space, which saves a good deal of money in I/O racks and housing.

ETHERNET I/O

According to Terry Biederman, Waterford Township DPW director, “With Opto 22, there’s a continuing evolution of the I/O and it just makes good sense to take advantage of the features, functionality and costsavings the company’s latest technologies provide.

“I like the Ethernet I/O implementation. We use it in the controllers and for the I/O,” Biederman continues. “We have two remote terminal units (RTUs) in the main office—a main one and a backup. These are connected to a personal computer in the office with an Intellution human-machine interface application. All of the RTUs in the field with Opto 22 PACs use the Opto operator interface software. The remote RTUs generally connect back to the home office with UHF
(ultra-high frequency) radio.”

Biederman says that there was “a ton of programming” to set this system up—especially for all the monitoring in each remote site. The system looks at such things as digital intrusion devices, pumps, valves, pressure sensors, temperatures, chlorine analyzers, weigh scales, variable frequency drives and motors. The system has a total of about 2,500 I/O points with about 4,600 tags in the Intellution database.

FEW FAILURES

“I bought the Opto system 11 years ago because of the PC foundation and the flow chart programming,” says Biederman. “I much prefer that to ladder logic. Opto has robust, optically isolated I/O devices and a good graphics package—plus it’s very cost competitive. We’ve also had very few failures over the 11 years of service.”

For more information, search keywords “Ethernet I/O” at www.automationworld.com

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