Thermoplastics such as Polyvinylchloride (PVC), Acrylonitrile-Butadiene-Styrene (ABS) and Polyethylene (PE), are popular choices for potable watermains and sewage forcemains owing to advantages over traditional materials such as Ductile-Iron (DI) and Steel. Unfortunately, the physical properties give thermoplastics their comparative edge over metallic pipes, also make them poor candidates for traditional non and minimally invasive acoustic leak detection and condition assessment techniques. This is because plastics pipes are better at absorbing sound than transmitting it.
Another complication is that is that failure modes for plastic pipes differ from those of iron pipes. While wall thickness measurements can be sufficient for remaining service life prediction for iron pipes, research has shown that at the time of failure, plastic pipes are often as thick as they were at installation. Rather, many plastics pipes fail because they have become too brittle to handle pressure transients or changes in surface loading or have become too deformed to properly distribute stresses. Likewise, changes in material properties of the pipe-wall can affect the quality of bonds and the tightness of joints leading to leaks.
ICONAC’s Tonal Pipe AssessmentTM (TPATM), has been used to assess PVC and PE watermains ranging in size from 150 to 250 mm overcomes these challenges through a SODAR type system that takes a different approach than conventional, acoustic time of flight or ∆T systems. Using a sound source that emits controlled spectra TPATM matches its test frequencies to the natural frequencies of the pipe wall. Additional measurements using a Thermodilatohydrometer, helps to to correct for in-pipe attenuation and scattering due to bubbles.
Following inspection, ICONAC uses measured data together with operational history, manufacturer specifications, industry standards and public research literature to score each plastic pipe segment according to an empirically supported classification matrix:
Within “x” Years
Within “x” Years