Page 134 - Trenchless Technology Piping Installation and Inspection

100 Cha pte r T h ree

Method Procedures
Drag Designed to remove hard deposits and nodules. This is made
scrapers up of spring steel scrapers mounted on a central shaft. These
scrapers remove deposits as they are winched through the
pipe. The central shaft is fitted with a towing eye at each end
to allow the scraper to be pulled back if necessary. These are
available for all pipe sizes ranging from 2 in. (50 mm) to
12 in. (300 mm).
Power boring Hydraulically powered device utilized to remove tuberculation
and encrustation from the water pipes. The device is a rack-
feed boring machine, a compact, diesel-powered unit using
hydraulic pressure to rotate steel cutter blades at 750 rpm
through the pipe.
High- High-pressure water jets are pulled through the pipe so
pressure high-velocity water blasts deposits and films from the pipe
water jetting surface.
Poly pigging This is similar to soft swab pigging except that it differs in its
construction. For softer scales, the pig is simply foam covered
by a plastic shell, while for harder scales abrasive materials
are adhered to the pig’s exterior.
Air scouring Volumes of air and water are alternately introduced to the pipe
through fire hydrants, creating turbulence that scours film,
and lifts and transports sediment.
Rodding Uses an engine and a drive unit with sectional rods. As blades
rotate, they break up the deposits and loosen the debris.
Balling A threaded rubber cleaning ball that spins and scrubs the
interior of the pipe as flow increases in the pipelines.
Flushing Introduction of alternatively high flow rate of water into the
pipes, removing floatables, sands, and grids.
Soft swab Foam plug is forced through the pipe using water.
pigging
Chemical Acid is circulated through a closed system, dissolving mineral
cleaning scale, biological growth, and corrosion by-products. Finally
the pipe is flushed and disinfected. Some common chemicals
used are H S gas, bioacids, digester, enzymes, catalysts,
2
hydroxides, and neutralizers.
Scooter This is a hydraulic method. Round, rubber-rimmed, hinged
metal shield is mounted on steel framework on small wheels,
which works as a plug to build a head water. This action
scours the inner walls of the pipeline.

Source: Adapted from AWWA M28, Rehabilitation of Water Mains.
TABLE 3.2 Water Pipe Cleaning Methods