Specifications Part 1 - Water Supply, Sewerage and Tube Well Works

14.19.1.1 As the rod is thrust inside, the machine also is drawn towards the manhole.The rod is pulled in and out in quick succession when the tool is engaging theobstruction, so as to dislodge or loosen it. When the obstruction is cleared, therod is pulled out by means of clamps keeping the rod rotating to facilitate quickand easy removal. The various tools attached to the rods are shown in Fig. 8.3.14.20 Scraper14.20.1 This method is used for sewers of diameter larger than 750mm. The scraper isan assembly of wooden planks of slightly smaller size than the sewer to becleaned. Where the scrapers cannot be lowered through the opening of amanhole, the scraper has to be assembled inside the manhole. The scraperchains, attached to a control chain in the manhole into which it is lowered, isthen connected to a winch in the next downstream manhole by means ofchains.14.20.1.1 The winch is then revolved to push the debris ahead of the scraper. Theheading up of the flow behind the scraper and the water dropping from the topof the scraper will also assist in pushing it in the forward direction. This ensuresthat the bottom and the sides of the sewer are cleaned thoroughly. Thescraped debris is removed manually.14.20.2 Circular scrapers are used on small sewers below 350mm dia for cleaning thebody of the line. They are commonly known as discs and these discs are eitherof collapsible type made out of metal or a wooden pair separated about 200mmapart by steel rods.14.21. Automotive Suction and Jetting Machine :14.21.1 The high velocity sewer cleaner makes use of high velocity water jets toremove and dislodge obstructions, soluble grease, grit and other materials fromsanitary, storm and combined sewerage systems. It combines the functions ofa roding machine and gully emptier machine. Basically it includes a highpressure hydraulic pump capable of delivering water at variable pressure uptoabout 80 kg/cm² through a flexible hose to a sewer cleaning nozzle.14.21.1.1 The nozzle has one forward facing hole and a number of rear ward facingholes. The high pressure water coming out of the holes with a high velocitybreaks up and dislodges the obstructions and flushes the materials down thesewer. Moreover by varying the pressure suitably, the nozzle itself acts as ajack hammer and breaks up stubborn obstructions. (A separate suction pumpor air flow devices may also be used to suck the dislodged material).14.21.2 The entire equipment is usually mounted on a heavy truck chassis with either aseparate prime mover or a power take off for the suction device. The highpressure hose reel is also hydraulically driven. The truck also carries freshwater tanks for the hydraulic jet and a tank for the removed sludge and thevarious controls grouped together for easy operation during sewer cleaning.The manufacturer's operating and servicing manuals should be carefullyfollowed for best results in the use of the machine.Urban Administration & Development Department Page 171