20 August 2009

Wireless sensors keep eye on water system woes

After a disaster hits, water services need to keep flowing.

With that in mind, there is now a plan afloat to outfit the Irvine, Calif., water system with sensors that will alert officials when and where pipes crack or break, hastening repair.

“When an earthquake occurs and infrastructure systems fail, continued service of the water network is most critical,” said Masanobu Shinozuka, lead project investigator and civil and environmental engineering chair at University of California Irvine. “Before anything happens, I’d like to have a pipe monitoring system in place to let us know when and where damage occurs. It could minimize misery and save lives.”

About 240,000 water-main breaks occur per year in the U.S., according to the Environmental Protection Agency. One case in point, in December, a burst sent about 150,000 gallons of water per minute onto a busy Maryland road, stranding motorists. Water system failures waste up to 6 billion gallons of drinking water every day, officials said.

New CD-sized sensing devices that attach to the surface of pressurized (drinking water) and nonpressurized (wastewater) pipes can detect vibration and sound changes that could indicate pipe problems, said inventors Shinozuka and Pai Chou, electrical engineering and computer science associate professor. Through antennae, the sensors will relay information wirelessly to a central location for recording, processing, and diagnostic analysis.

Initially, the sensor network will cover about 1 square mile of the local water system; eventually, it could encompass more than 10 square miles, the largest of its kind to date. A small-scale pressurized water pipe network designed and built by UCI researchers found this type of damage identification works well.

The research team now is designing a system that functions underground as well as over a larger area. The main hurdles are powering the sensors (batteries and solar energy are not strong enough), making them more cost-effective and robust in tough environments, and achieving long-range wireless communication efficiently and accurately, Shinozuka said.

Using existing pipe networks, the team will then test and calibrate the sensors by simulating and monitoring pressure changes equivalent to those arising from actual pipe damage. The sensors will complement an existing Supervisory Control and Data Acquisition (SCADA) system.

“SCADA sensors are too sparsely placed for identifying damage with the kind of precision we desire when a large earthquake or other natural hazard affects many locations,” Shinozuka said.

“An isolated malfunction is far different from a situation in which pipes break all over the place,” he said. “Our next-generation system will inform us as soon as possible when and where damage occurs and to what extent so we can better mitigate the consequences.”

As the research progresses, the team plans to develop methods of rapidly repairing pipe damage at joints and other vulnerable locations.

For related information, go to www.isa.org/sensors.