When Pipeline Technologies Inc. (PTI) asked Sigma Tech to build a new, faster acoustic monitoring system for them, we responded quickly to this opportunity, integrating the hardware and developing the software in less than six months. The AH-2 System is used to detect deterioration in Prestressed Concrete Cylinder Pipes (PCCP) that are used to deliver water to homes throughout the country.

The system needed to portable, run unattended and most importantly locate problems in water pipelines to a few feet of accuracy. The systems need to be rugged because they would be outdoors, and subject to extreme variations in environmental conditions. The system monitors the pipeline by inserting hydrophones via access points along the pipeline, listening to the sounds carried on the water inside the pipe in real-time.

The AH-2 system has two main components, the Remote Acoustic Signal Processor (RASP) and the Central Acoustic Processor (CASP). The method of operation is to place multiple RASP units with hydrophones spaced approximately 1000 feet apart along the pipe to be monitored (which could be miles long). The RASP units run off of car batteries and collect data in real-time, saving only data that corresponds to acoustic data of interest.

Two AH-2 RASP Units during the FAT

A notebook computer is used to connect to each RASP once a day to upload data over the ethernet port. The collected data is brought back to the CASP unit and analyzed to determine if the acoustic data from multiple units localize.

The decision was made early on to use COTS hardware as much as possible. The RASP processors are Pentium 233MMX CPUs on a PC/104 motherboard. Data Acquisition is provided by an 8 Channel A/D. Timing and Position data is provided via GPS. The RASP units run Windows95 with 64MB RAM, and 1.6GB Hard disk.

The RASP reads data from the A/D using the DM5416 ProgrammerPak™, and time tagged from GPS data via the TrimbleGPS library. The data is then filtered, and passed through an energy detector algorithm which were implemented using the USPL. Detections that matched specified parameters are then logged and saved for later analysis. Important information can be displayed on the RASP via the front panel mounted LCD display, or via a remote control program over the ethernet. Additional RASP features are hot-swap battery support, analog headset jacks, remote shutdown, and battery monitoring.

By using our standard ProgrammerPak™ software libraries Sigma Tech was able to slash a significant amount of development time from the project. The ProgrammerPak™ libraries used were Universal Signal Processing Library (USPL), TrimbleGPS, DM5416, Programmer Utilities (ProgUtil). All new code developed was in C++ using Borland C++ Builder.

The system had its Factory Acceptance Test (FAT) during April 1998 in the Arizona desert monitoring a unused portion of the world's largest PCCP (a whopping 21 feet in diameter). The AH-2 System passed all the tests with flying colors. PTI is now using the system to monitor water pipes commercially throughout the country.

Enhancements to the system is now under discussion, such as transmitting the data over a wireless network and provide data over the Internet. This would allow the system to be controlled and monitored completely by remote sites all over the world.

If you would like more information on this project, portable data collection units, or Sigma Tech capabilities in general, drop us a email at info@sigmatechcorp.com or call us at (540) 439-8000.

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Last modified: December 18, 2005