From the magazine

Fantastic acoustics

An unfortunate reality for asset owners and contractors around the world is that when it comes to prioritising sewer and stormwater maintenance a fair amount of guesswork is involved and, as a consequence, a degree of inefficiency and wasted resources is inevitable.

In first-world countries, an average of 65 per cent of all sewer networks are functioning normally on any given day. If it were known which lines constituted that 65 per cent, these lines could be excluded from maintenance programs, saving resources and enabling asset owners to target the most-needed areas. Unfortunately, it is not known which lines are affected and, perhaps ironically, the only way to find out is to use the very resources required to save them.

Recent efforts to address this conundrum, however, have seen the development of acoustic technology that provides a fast and highly effective pre-qualification for pipeline condition or, more specifically, overflow potential, without the need for entry into the pipe itself.


The Sewer Line Rapid Assessment Tool (SL-RAT) was developed by industry newcomer Infosence Inc. in conjunction with the University of North Carolina. The system can be described as a rapid “÷pre-CCTV’ pipeline inspection tool that uses sound instead of sight to evaluate blockage probability.

In contrast to CCTV inspection, it is designed to identify pipes that should be excluded from routine maintenance schedules rather than included. While it does not eliminate the requirement for CCTV inspection or cleaning, it is a cheap and reliable pre-qualifier for both.

The technology comprises two components: a transmitter and a receiver. Each component is placed at either opening of the upstream and downstream manholes of a section of pipe that has been identified for prequalification. Next, over the course of two to three minutes, the transmitter sends audible multiple frequency pulses into the pipe which are then “÷listened’ to and analysed by the receiver.

Following the sound transmission and analysis, the receiver then grades the pipe from zero to ten based on what it “÷heard’. If a grade of zero is given, this means nothing was heard and the sound was thus completely blocked due to some characteristic of the pipe.

Alternately, if the grade given is a ten, this means there was very little sound blockage (or no blockage at all) during the sound wave’s passage through the pipe.

The benefit of this information is that it enables a very quick pass/fail assessment of the pipe and identifies it as either a candidate for further investigation or elimination from the maintenance program altogether. The resultant benefits of which are enormous.

Tried and proven

Empirical data obtained from millions of metres of field trials and contracts across the US, Europe and now here in Australia and New Zealand have demonstrated that this technology reduces the misallocation of CCTV and/or cleaning resources by an average of 65 per cent.

Additionally, the system enhances qualified targeting of resources by 286 per cent and either decreases funding requirements of routine maintenance contracts by an average of 43 per cent* or increases economic efficiency of routine maintenance contracts by an average of 175 per cent*. In fact, the SL-RAT is so efficient that the realised payback period for a single unit is less than two weeks.

The SL-RAT is currently deployed and endorsed by over 50 authorities worldwide where typical applications include prequalification for condition-based maintenance, post-cleaning quality insurance, and quick and effective pre-commissioning assessment of new subdivisions.

Recently ratified by the US Environmental Protection Agency following a comprehensive and independent study in mid-2014, trials are currently underway for the SL-RAT down under via the Technology Assessment Group initiative – the results of which will be available in early-2015.

*Empirical data obtained by comparing results achieved from the deployment of SL-RAT in conjunction with conventional CCTV and cleaning technologies in the field (as opposed the use of conventional technologies alone).

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