GPS/GIS automates mobile gas leak detection

Background
The current leak detection vehicle system uses a Flame Ionization Unit (FIU) to detect methane gas in the atmosphere. The driver/technician receives a signal from the FIU that alerts them to the leak. Currently, there is not a device to record this data or any historical data about each driver’s daily leak routes. Handwritten documents regarding leaks found and handtraced maps are recorded for each day’s work. This system relies completely on the Leak Detection (LD) technician and the paper record trail. With the existing FIU, the LD vehicle leak surveys at low speeds of 3-5 mph, and the technician needs to constantly monitor the FIU readings. Also, the FIU has an 8+ second response delay from the point at which the methane sample is taken to the time that the sample is analyzed and the technician is alerted to a reading beyond the set threshold. The delay varies from vehicle to vehicle. At 3 mph, this is equivalent to 4.4 feet per second; from the point that the methane sample was gathered, a distance of 35.2 feet will be traveled before the FIU responds to an analyzed sample. The 35.2 feet does not take into account the added distance that is traveled for the technician to safely stop the vehicle after the technician is alerted. The LD technician now has to backtrack to the approximate location of the initial sampling point and localize the leak.

A leak is graded after it is found. The leak grade determines the LD technician procedures and the process in which the leak paperwork is started. Grade ‘A’ leaks are called in to dispatch, and a Leak Sheet is started for each such leak in the dispatch center. The LD technician must remain at the leak site until an emergency repair crew arrives. If the grading is ‘B’ or ‘C’, the LD technician starts the Leak Sheet and turns it into the LD clerk at the end of the shift. The LD Clerk starts the data entry from information on the Leak Sheet. The leaks are then tracked and reports printed on a daily basis.

Automated Leak Detection System
With the use of the proposed ALDS, many of the tasks performed by the clerk and the LD technicians will be completed by the ALDS soilware and other integrated systems. The proposed system will integrate several pieces of technology that are available today. These include laptop/portable PCs, GPS, wireless data communications, dead reckoning system (ring laser gyro), and GIS. The proposed system will use an existing FIU-equipped LD vehicle. The major difference is that the proposed system will allow for the collection of data in real time and the storage of historical data about the technicians’ daily routes. The databases on the PCs contain the real-time GPS coordinates and real-time leak sampling data acquired from the FIU. The ALDS software is based on GeoLink, the GPS/GIS system developed by GeoResearch, Inc., and allows for the tracing of the GPS coordinates over a digital basemap produced from the GIS. The GPS tracing is displayed in real time on the display of the PC overlaying the digital maps, at the same time recording the GPS and leak data to the PC. This removes the manual task of tracing a map by hand from the technician. When a potential leak is found, the integrated system automatically highlights and records where the leak occurrence took place. An electronic leak form will be available for the technician to complete and send via wireless data communication to a central location. This data will be maintained as part of a permanent data store. The GPS data and leak detection data is uploaded to the GIS and is stored in defined data format as historical distribution system data. The electronic leak form data is uploaded to the Leaks On Construction Tracking System application. With the proposed data communication, the appropriate field crew can be immediately dispatched to the location of the leak. With the power of the GIS, forecasting of leak trends and detailed analysis can be completed in a graphical or tabular format. After enough cyclical data are collected, leak routes may easily be combined or altered depending on their cycle frequency and geographic location. When changing these cycles and routes, remember that all standard code requirements must still be met to satisfy the Office of Pipeline Safety (OPS), other regulator agencies, and the internal operations for the gas distribution company.