INCRUSTATIONS IN WATER MAINS. (Continued.)

Progress, Volume II, Issue 10, 1 August 1907, Page 379

INCRUSTATIONS IN WATER MAINS. (Continued.)

By Thomas Ward, A.M. Inst. C.E., Member Association of British Waterworks Engineers. It certainly seems extraordinary that hitherto this subject should have received such scant attention. Fanning and Burton, well-known writers, scarcely allude to it. This ommission is surprising on the part of the latter as his book is recognised as the most up-to-date one. He strongly insists upon the coating of pipes by Dr. Angus Smith's method, and inferentially the conclusion can be drawn that this is a sufficient precaution to take. Experience, however, shews that it does not answer in all cases. With a few exceptions the minutes of the proceedings of civil engineers are silent on the matter. Jamiesons paper has been mentioned in my former article. Messrs. Henderson and Mansergh also have written about it. Preparatory to the latter' s report on the I,ancashire Waterworks in 1875, as mentioned in vol. 68, he was made aware that the discharging power of the original 8-inch main was seriously diminished and recommended that it be scraped, which was carried out in the year 1878 with great success, the apparatus used being that devised by J. G. Appold, modified by Thomas Kennedy, managing director of the Glenfield Company, Kilmarnock. The methods adopted consisted in making use of the pressure of water in the mains to drive scraping tools : its form and construction is shown in diagrams Nos.l and 3. The engineer to the Wakefield Corporation has another kind, and a company has been formed in England to take it up. The machine is somewhat in the form of an ordinary winch fitted with a winding drum worked by hand, carrying a chain working in a spurred wheel similar to a bicycle chain. This chain turns the wheel which works the cutter. The machine is fixed on the top of the ground and is placed on rails, and as the cutters work their way through the pipes it is pulled along the rails by an endless rope over a pully. The method of working is to take out one length of pipe over which excavation the apparatus works : another length of pipe is removed about 150 yards further along, from which place the debris from the encrusted pipe is removed. If the pipes are very much filled up, another pipe must be cut out at a much shorter distance than the above : but hitherto pipes have been cleaned out as far as this before a fresh excavation is required. This expedient is only suitable for diameters -of 3", 4", and 6". Before scraping was resorted to, new mains were laid and old ones taken up when much corroded ; or the mains were taken up and heated, which involved the substitution of another main. When another main to Wainui-o-mata is laid down the opportunity should be taken to thoroughly overhaul and clean the present mains. Pipes have also been cleaned by hand labour. The tool used is shown in diagram 3STo. 1. The cutting edge being of steel of the

same curviture as the internal diameter of the pipe against which it is pressed by the steel spring. As the cutter proceeds along the pipe rods are added. It is driven forward and backwards by men working on the excavations made by means of ropes : horses have also been used being attached to the apparatus by chains. The form of scraper now used is shown in diagrams 2 and 3. It consists of two distinct parts connected by a swivel joint. The front carrying the four steel scrapers, and the rear portion the steel propelling pistons. Leather discs intersected by radial cuts, and stiffened at the back by lead plates, are

placed behind the pistons : the cutting edges are set in such a way that should the scraper encounter anything in the shape of a projection such as a ferule screwed into trie pipe, the whole machine will slew or turn round, ana pass the obstruction without getting blocked, while the leather packing behind the pistons will fold back and pass any obstruction that can be passed by the pistons themselves. Originally, two sets of scrapers and two pistons were used on the one rod, but ov^ing to its length it could not be passed along bends in the pipes. To overcome this, one set of scrapers and one piston were taken off, and in place of the rigid iron rod, one with a

flexible joint has been substituted. By this means the machine has been made to pass bends of a radius 3| feet : this is shown on diagram No. 3. It is important to have two sets of scrapers of different diameters, so that when the scraper is inserted in the main for the first time the smaller sized pistons may be used, and after the main has been partly cleared, then the larger sized pistons can be employed. Operations of scraping must be continued during the night for two reasons, (1) to reduce the inconvenience to the public, (2) to prevent the detection of obstructions from being hindered by the noise of the traffic. Opinion is now steadily growing in favour of providing conveniences for scraping of pipes when new water-works are contemplated. The mains should be subdivided into areas and sections having hatch boxes at suitable places : each box being placed in a man hole having a moveable cover at the street surface, and a bottom drain to remove water. Box covers may then be opened at any time without injury to the road, and without damage to the mains caused by cutting out lengths of piping. Sketch plans of hatch boxes are shown in diagram No. 4, and their position in the man-hole by diagram No. 5 The following is the descriptoin of the system of cleaning a 6in. main at Kendal, contributed to the journal by the British Waterworks Engineers' Association, by Mr. Ritson, engineer to the Kendal Corporation :— " When everything was in readiness the scraper was inserted into the first hatch box at the reservoir. The pipe line across the fields having been previously pegged out, a number of active young men were posted along the line of main at intervals of twenty-five yards, with instructions that directly the scraper is passed underneath (which can easily be distinguished by the low rumbling sound it makes) each man had to shout to the man in advance, "Passed," and then proceed 25 yards in advance of tne man farthest away, and so until the scour pipe is reached. The turncock was instructed to turn on the water at a given time, and also to listen for the inspectors' signal whistle, and follow the instructions of the code of signals given to him. The scraper moved off directly the water was turned on, but it only proceeded 130 yards when it stuck fast. When the scraper sticks its position can be located by means of a stethoscope from the sound of the water rushing past. The position of the stoppage in this case having been speedily located, the water was turned off, the main cut, and the scraper removed. It was then found that the stoppage was due to about 12 lbs of lead the result of a badly run joint. The pipes having been made good the scraper was once more inserted, and it came down as far as the scour pipe. In the evening the scraper was again set in motion, and it arrived at the second hatch box in a short space of time, bringing with it a goodly quantity of filth and corrosion. The next day the scraper was again inserted at the reservoir in the hatchbox, and the water turned on, when an exciting chase took place, for No 2 hatchbox (a distance of 2,523 yards) was reached in 17 minutes. A good deal of corrosion came down again and the main had to be well flushed. In the evening the scraper with knives set to 5f in., and fitted with 4| in. diameter pistons was inserted in No. 2 hatchbox. The men were instructed to lie down at intervals of 20 yards, with ear to ground, on the line of pipes. The water was turned on and the scraper moved off gaily, the inspector following it up with his stethoscope, but after a journey of 40 yards it stuck. The

sluice valve was turned off and opened suddenly in the hope of again setting it in motion, but without success. The pipes were then bared and well rapped with a hammer which had the desired effect. The scraper moved off another 40 yards and stuck again. The same operations were repeated but failed. A loosely rolled wisp of hay was inserted into the main behind the scraper and the water turned on, but all to no purpose, it had to be cut out. On examining the interior of the main at several spots between No. 2 and 3 hatch-boxes, it was found to be so badly corroded that in some places there was barely two and a half inches of waterway through it, and as the pipes had not been treated with Dr. Angus Smith's composition, the carbuncles of oxide of iron had coalesced to such an extent, and were, moreover, so firmly fixed to the interior surface of the pipes, that it was regarded as next to impossible to scrape this length (66 yards), and a new main was laid instead. Operations were now directed to scraping 830 yards of 4" main, which was known to be badly corroded. It was feared, however, that the task would be both laborious and expensive, unless some means could be devised which would admit of the work being done expeditiously and well. A local blacksmith was brought into requisition, and a set of steel spring scrapers was made somewhat on the model of the 0" scraper, but without the rear or propelling pistons, but with a ring formed in the front of the apparatus to hook on a rope. A hundred yards of §" strong Manilla hemp rope, a similar length of §" steam tube, a couple of cast iron clips for 4" pipes with rubber bushes or cylinders (used for speedily joining up the ends of cut pipes), and a crab winch completed the kit. The main was cut at intervals of 90 yards. L,ength after length of steam tube was screwed together, and passed along the main until it emerged at the other open end. The rope was then hooked into an eye made in the front length of tube, and the whole withdrawn. One end of the rope was then

attached to the drum of the winch and the other end hooked'to the scraper before being inserted in the main. A piece or four inch pipe was cut to length, and the rubber brushes slipped over the ends of the cut main, the whole evenly and tightly clamped together by means of the clip joint. ~~* A gentle stream of water was turned on and the scraper slowly drawn through the main by means of the winch. This operation was repeated twice, and the main well flushed after each scraping ; and on completion the corrosion had been completely removed, and the pipes appeared almost as good as new. The cost of scraping amounted to 6.32 d per yard. Pipes coated with Dr. Angus Smith's composition can be scraped quite easily, and at cost of from 4d to 5d per yard. The success of the scraping of the 4" main was so marked that it was determined to make another attempt upon the 6" main where operations had ceased. Accordingly the scraper was set to full size, and inserted into No. 2 hatchbox at 10 o'clock at night. Men were posted at intervals of 10 or 12 yards on the line of main, with strict orders to listen with ear to the ground. The scraper moved forward after the water was turned on at a fairly rapid pace, and for a time was lost, but eventually located by means of the stethcscope, and the mud, filth and encrustation at No. 3 hatchbox showed that it was doing its work. After a good deal of dodging such as turning off the water and putting it on again suddenly, passing several lengths of | in. steam tube down the main to try and force the scraper back a bit, at last it came into No. 3 hatchbox bringing with it a ton or more of iron rust, the shattered remains of carbuncles. The total cost of scraping the 3,190 yards of 6" main amounted to 4.08 per yard. The result has been that the water supply has been so much improved, without the anticipated extensions of the mains, that a constant supply is able to be given and the total cost under £55.

Place Diameter. Length of Total. Cost per I yard Obstruction. Gain in delivery after scraping. Year. main miles yds. 1 440 4 660 1 1500 1 586 £ »dper cent. 1877 1878 1880 Oswestry Lancaster Duiham {Y 16" 8" 12" 121 30 91 2 93 2 2 9 1 Large stones, lead, and defective pipes Peaty matter Lead spade, spike, waggon spring Stones, lead, crowbar, &c 54.4 56.1 55.6 1880 Bradford 18" 4 1100 634 18 6 1881 Halifax N.^. 12" r 16I 12" f 13" { 11" 6" 6" 1 573 2 2 2 1 056 3 1232 J 1 785 1 880 2 792 91 192 9.3 6 5 1882 Exeter Mussels stones, lead 27.6 1883] 1885 J 1885 1886 1887 Whitehaven 516 11.1 Bristol Denbigh Omagh 35 150 53 33 13 6 2.9 Stones Stones, gravel, lead Lead , defective cast30 0 6" 1887 1888 1890 Halifax LHverston Dundee 6" 6" 15" r 9- ! 8" 8" 10" 24" 776 21 72 256 65 9.8 17 4 ings 1 2 I ) 1 440 1080 6 880 5 594 Wood, stones 1890 Dumfries 113 3 Stones 1890 1891 1891 1892 Scarborough Newport Lanark Roubaix (F>nncr) 62 50 75 242 6.7 11 1 1.57 6.4 Lead . I cad, wood stones. -f 33 7 16ft. taken off pumping engine 1892 Purntisland 8" 3 1320 252 9 02 Piece wood 2ft 3" x s\" x 5", lead 1893 1893 1894 Bridge of Allen Thurso Stirling 6" 6" 1 3 3 1320 35 7 8" Stones, lead, broken 1894 1895 "Waterford Cuper Fife 13" 7" 8 3 880 211 66 2.6 pipe Same Piece broken pipe, rabbit About 400 stones.' 40 52 30 1895 Merthyr Tydvil 14" 5 617 318 8.01

TABLE GIVING SUMMARY OF COST OF SCRAPING WATER MAINS B^ PRESSURE SCRAPER. (From Minutes of Proceedings, Inst C.E.)