Not just a pipe dream!

US water facilities and those around the world are faced with mounting operational and maintenance costs as a result of aging pipeline infrastructures. The ability to monitor and control the infrastructure is no longer a pipe dream but is on its way to becoming reality thanks to wireless sensor networks. PipeNet, is a system designed by researchers at Imperial College in London and CSAIL at MIT in conjunction with Intel Research, to collect hydraulic and acoustic/vibration data at high sampling rates as well as use algorithms for analyzing this data to detect and locate leaks. A study by the EPA (Environmental Protection Agency) estimates that water utilities will need $277 billion over the next 20 years (2003-2023) to install, upgrade, and replace infrastructure. Unfortunately, identifying the high priority areas is a non-trivial task because of the scale and age of the pipeline infrastructures. Failures of large diameter bulk-water transmission pipelines are of greatest concern as these are supply critical systems. When these failures do occur, there are dire consequences including loss of life, severe interruptions in service, degraded fire fighting ability, damage to adjacent infrastructure and buildings, and of course the multi-million dollar repair bills.

PipeNet is a system based on wireless sensor networks which aims to detect, localize and quantify bursts and leaks and other anomalies in water transmission pipelines such as blockages and malfunctioning control valves. The system was based on Intel Motes (the 1st generation of the Imote2 devices available today) to provide remote monitoring in near real-time with support for high data rate time synchronized data collection from multiple locations. This is a significant change from current data acquisition practices of using portable data loggers with a low duty cycle and limited remote monitoring stations that do not have the capability to do local processing or high-bandwidth transmission.

The Motes were responsible for the data collection, local signal processing and relaying of data to the second tier consisting of the Stargate platform that was to relay the data back to the backend server via a GPRS modem. A special sensor board was also designed to interface to the Mote to accommodate the various analog sensors used in PipeNet. The clusters contained pressure sensors and pH monitoring sensors combined with water level monitors and pressure monitors. The mote could be configured to trigger data acquisition on a channel remotely when a monitored channel exceeded some threshold. Acoustic and vibration data analysis was used to detect and locate small leaks which are difficult to identify with hydraulic data. Vibration signals collected showed differences in the mode of wave propagation if a leak was detected. Leaks also manifested themselves in the acoustic signal which propagates uniformly in both directions away from the leak by the escaping water flowing through the rupture in the pipeline.

The Motes communicated from the manhole to the Stargate based gateway deployed on a nearby lamppost. The Stargate, the GPRS modem and 802.11 radio were powered from the power lines at the lamp post. The Intel Mote was connected to the Stargate through its UART interface acting as a bridge between the Stargate and the motes on the pipes. This cluster head was responsible for forming the sensor network, converting the configuration data coming from the Stargate and passing it to the correct sensor node as well as delivering the data collected via the reliable transport protocol to the Stargate where it was converted back into data files. These files were periodically sent to the backend server running in the lab via the GPRS link. The Stargate was equipped with an 802.11 link to facilitate drive-by access for on-site configuration and debugging as well. Data transfer was handled via standard Linux tools, and the data files were then loaded in a Postgres database that stored the individual sensor readings. This gave users the ability to browse these sensor readings by connecting to an Apache Web server running on the server. The web site used Google Maps/Google Earth to allow users to select and browse the sensor locations of interest. Once users selected a sensor location, they could retrieve data corresponding to a user-specified date / time range and sensor type to visualize the data.

Using the leak localization algorithms they developed, the research team was able to localize leaks to within 30 cm. The long term monitoring of pressure and acoustic signals in particular pipes will also facilitate the development of more accurate pattern recognition and classification models in the future. The next revision of the PipeNet system is using the Imote2 platform which integrates many essential components to enable high performance and energy efficient data processing. The XScale processor on the Imote2 has dynamic voltage and frequency scaling capability to allow applications to balance performance and energy needs by selecting speeds between 13 and 624 MHz. In addition, the processor includes a DSP co-processor to accelerate common data analysis primitives (e.g FFT, compression) thereby greatly improving performance and energy efficiency. This performance advantage will allow users to carry out the analysis and data reduction in real-time, thus reducing storage and power. Finally, the Imote2 includes 32 MB of SDRAM and Flash enabling the decoupling of data collection and communication with a richer peripheral support that will provide higher data acquisition rates and improve sensor integration.

PipeNet is the future of pipeline monitoring providing the capability to automatically detect leaks and bursts of water in the transmission pipelines; real-time operation with few false alarms; inexpensive to produce, install, and maintain; high-frequency data collection; the ability to differentiate between sensor and system faults; and a flexible reusable data-flow based programming environment. This system will not only improve our ability to monitor large scale water supply systems, but to conserve our natural resources and use them efficiently.