Case studies: Wireless remote monitoring
Wireless communications were used to get a flowmeter signal to a control system at the Wards Island Water Pollution Control Plant (WPCP) New York City Dept. of Environmental Protection (NYCDEP). Monroe County Pure Waters connects life safety equipment wirelessly at two plants on the south shore of Lake Ontario, Van Lare and Northwest Quadrant in Rochester, N.Y.
Wireless flowmeter output at WPCP
The Wards Island Plant is situated in the middle of the New York City’s East River between the Boroughs of Manhattan, Queens, and The Bronx, processing upwards of 275 million gal per day (MGD) of wastewater. During a biological nutrient removal (BNR) demonstration project designed by Aecom Technology Corp. (NYSE: ACM), a flowmeter signal needed to be input into the new control system for the BNR pilot program being done. Ordinarily this is simple enough; however, the space between the vault and the building was completely full of underground channels, conduit, and other assorted items and putting another conduit in the ground was not an option. Going overhead was equally impractical, and to further complicate things, a large-diameter pipe arbor stood squarely between the vault and the building. The designer’s solution was to set up a simple point-to-point link between the instrument and the building.
Lawrence (Larry) Pendergast, Aecom I&C engineering manager, said, "At Wards Island WWTP, a low-tech unlicensed, 900 MHz, point-to-point wireless transmitter and receiver pair installation was the only means available to send the aeration tank influent flow, meter chamber high level, and sump pump system fail alarm signals from a metering chamber to a DCS [distributed control system] control unit about one-eighth of a mile away. Since a 30-in. diameter steel aeration header was directly in the line of sight, a key to the successful implementation was that the designed gain and line-of-sight placement of the Yagi antennas was verified by field testing prior to purchasing any equipment. DCS monitoring of a communications fail signal from the receiver unit provided for the requisite distributed control system (DCS) alarm and fail-safe control programming to maintain the last good flow value for flow control to each of the four aeration tank passes."
Emergency showers monitoring, Monroe County Pure Waters
Monroe County Pure Waters, Rochester, N.Y., operates two plants on the south shore of Lake Ontario, Van Lare and Northwest Quadrant, with a combined capacity of 160 (MGD). Jeff Helfer, the facility’s instrumentation guru, needed a way to easily and inexpensively monitor remote processes without the time and expense of installing wiring. Using intelligent gateways and HART-capable wireless transmitters, Helfer was able to easily set up a large network of wireless sensors. While no control function is being done, a stark departure was the installation of wireless equipment on emergency showers located in remote areas of the plant.
As Helfer explained, "We needed to be able to get the network set up fast and at minimal cost. Wireless seemed to be the way to go, and from the first it proved to be a good decision. The use of wireless on life safety equipment was a gamble, but the system is solid and reliable. We actually use the existing wiring as a backup to the wireless system. We are very pleased with the coverage and performance—we are covering the entire plant" with two gateways.
As regards cost and durability, Helfer said, "We saved hundreds of thousands of dollars by not hardwiring the system. This is no exaggeration. The additional savings in time more than paid for itself. As for durability, the recent heavy snows buried many of the transmitters—amazingly, the network continued to operate without any interruption. It is an impressive technology."
– Daniel E. Capano, email@example.com, is president of Diversified Technical Services Inc. of Stamford, Conn., and serves as vice chairman of the Stamford Water Pollution Control Authority; edited by Mark T. Hoske, content manager, Control Engineering, firstname.lastname@example.org.
www.controleng.com/archives March, with this article online, see the products used for these applications and link to a Control Engineering industrial wireless tutorial on antennas, including yagi.
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Attend the March 10 webcast (archived afterward) on "Integrating wireless into an industrial Ethernet application."
Monroe County Pure Waters application used Rosemount Smart Gateways and HART capable devices and THUMs from Emerson Process Management. Emerson Process Management offers Smart Gateways and THUMs (The HART Upgrade Module) for instrument-level wireless communications. HART stands for Highway Addressable Remote Transducer. Two of the gateways were used for the network.