After winning the NASTT Product Innovation Award and the PURE Award for Innovation, South West Water, England, both in 2013, Electro Scan projects have been growing in demand across the globe – so much that that Electro Scan Inc. opened two new offices – one in Toronto, Canada and one in London, England.
Following two years of innovative projects in England and Northern Ireland, one of which allowed Liam MacFarland of Wessex Water to win UKSTT’s ‘Young Engineer of the Year’ Award, Electro Scan Inc. finally opened Electro Scan (UK) Limited. Electro Scan can now bring its sewer leak detection system, services, and support directly to UK Water and Sewer Companies (WASC). Since announcing the opening in September of 2014, Electro Scan (UK) Limited has already been working with three WASCs on different projects, which are scheduled to start in the spring.
The low-voltage inspection system locates and measures (in litres per second) estimated defect flows in pre- and post-cured-in-place pipes (CIPP). In accordance with ASTM F2550-13, Electro Scan’s products detect fa
ults typically not seen by Closed-Circuit Television (CCTV) cameras or heard by acoustic sensors, allowing engineers and directors to find and quantify defects in drains that typically go undetected. The results provide decision-making information for rehabilitation planning and certification of rehabilitation projects.
This was the case with the recent Electro Scan project in the City of Surrey, British Columbia, Canada. The City of Surrey has one of the largest sanitary sewer systems in British Columbia, serving approximately 130,000 customers with over 1,500 km of sewer pipes ranging in diameter from 150mm to 1200mm. Surrey, like many cities, has issues with inflow and infiltration (I&I) stemming from aging infrastructure. Surrey selected 2.2km of sewer near their City Centre, and looked to Electro Scan technology to provide quantitative data regarding their infiltration issues. Due to inconsistent CCTV inspections and rehabilitation efforts that didn’t seem to be working, Surrey had Electro Scan, Inc. evaluate 27 sewer mains and 65 private sewer laterals.
How the Technology Works
The Electro Scan probe releases a focused array of low-voltage high-frequency electrical current, of only 10 volts and 40 milliamps, which automatically locates and quantifies all defects in non-conductive sewer mains and laterals.
Most sewer pipe materials are electrical insulators. A defect in the pipe that leaks water will also leak electrical current. For a constant applied voltage, the larger the defect, the greater the electric current that will pass through the pipe wall. This is also the case for water in that for a given water pressure, the larger the hole, the greater the flow.
Since sewer pipe materials are generally asbestos cement, brick, clay, concrete, plastic, and reinforced concrete, i.e. all non-conductive materials that naturally prevent electricity from passing through or along the wall of a pipe, no electrical current should ever be able to “leak” or escape from inside a pipe; unless, there is a crack or break in a pipe.
As the Electro Scan probe passes through the pipe, it measures the variation of electric current flow through the wall of the pipe, then through the ground to an electrode on the surface – a metal stake driven into the ground.
Taking an electrical measurement every 14 milliseconds, the data is transmitted back up the CCTV truck’s cable and reel, and then to the Electro Scan controller. There, the data is synched and delivered to the truck’s on-board PC which records all the data and operates the system via Electro Scan’s desktop application software. Once a scan is complete, the software then sends the scan’s “raw data” to the web-based processing and viewing platform, where it is automatically post-processed, quantified, and displayed to anyone who has an account for that particular project or client. Additionally, an estimated Litres Per Second (l/s) infiltration rate is assigned to each of the defects, and then the pipe, as a whole.
Project Results
The scanning of the 2.2 km of pipe took only four days. In the 27 sewer mains, Electro Scan was able to locate 801 defects with a combined estimated defect flow of 23.53 l/s. The single worst sewer main segment measured defects flows of 4.0 l/s or 17% of total defect flow from all sewer mains. In the worst pipe segment, Electro Scan detected 94 places that water was able to escape the pipe wall, where CCTV operators were only able to call out two defects. Additionally, Electro Scan determined that the ten worst sewer mains were responsible for 16.6 l/s or 71% of the defect flow from the 27 mains evaluated.
Electro Scan evaluated 65 sewer laterals and found 254 defects that measured an estimated defect flow of 5.4 l/s. Of the 65 laterals that were evaluated, the fifteen worst sewer laterals were responsible for 4.8 l/s or 91% of the defect flow.
1,055 total defects were discovered, with a total defect flow of 28.8 l/s. The sewer mains were responsible for 81% and laterals being responsible for 19% of total defect flows. If the city addresses the ten worst sewer mains and fifteen worst laterals based on the quantified defect flows, total defect flows would be reduced by 74%, while only rehabilitating 37% of the sewer mains and 23% of the laterals evaluated.
The City’s Engineering Department is currently using these results to develop and implement a cost-effective rehabilitation program based on quantified defect flows.