Acoustic and Seismic Sensors
PSI’s Proactive Infrasonic Gas Pipeline Evaluation Network (PIGPEN) is an autonomous distributed sensor system that detects and reports excavation activity and its location. Third-party intrusion, i.e. unauthorized excavation that accidentally strikes and damages or ruptures a pipeline, is a large cause of loss to gas pipeline integrity. The PIGPEN sensor system provides pipeline operators and intruders with a real-time warning of right-of-way encroachment and excavation activity near a pipeline. Early warning provides pipeline owners the ability to respond to the potential intrusion in time to prevent pipeline damage, and thus preclude incurring the additional cost and risk of repairs.
PIGPEN is based on infrasound detection. Because of their low frequency, infrasound waves are less susceptible to dissipation than normal acoustic frequencies and travel long distances. Traditional infrasound sensors are large, susceptible to environmental effects, and expensive. PIGPEN employs innovative, inexpensive, rugged, high-sensitivity infrasound sensors developed by PSI, and integrates them with signal processors and communications hardware to form a pipeline encroachment detection system.
The basic PIGPEN sensor system comprises:
a) Discrete unattended geographically-distributed sensor packages, buried in shallow ground sites, each containing:
i) A high-sensitivity, low-noise low-cost sensor detecting low-frequency seismic and acoustic waves (infrasound), generated by excavation equipment, that propagate to the sensor site.
ii) Digital signal processing (DSP) for interpreting and reacting to the sensors signals
iii) A micro-controller for activating and de-activating components, based on sensor activity, to minimize power consumption
iv) A wireless communications transceiver for data transmission within a local network
b) A Network Interface Box (NIB), that coordinates communication among sensor packages and interfaces with the pipeline operator or other parties
Individual sensor packages are buried at intervals of 100 – 500 m, depending on soil conditions, near and around the pipeline. The firmware in each sensor continually processes received signals to distinguish threats, as defined in a pre-programmed library, from benign sounds. When any individual sensor detects a threatening event, it activates its communications section and transmits information to neighboring sensors within its local network. This sensor cluster then operates collectively to localize the threat. If, within its localization accuracy, the system determines the threat to be within hazardous proximity to the pipeline, it transmits a warning to pipeline operators or excavators.