62 Mechanical removal of Deposit from Water Mains* 



The existing main was 6 inches internal diameter, with a 

 length of 4312 yards, and a fall of 216 feet. As the population 

 to be supplied did not much exceed 4000, this pipe should under 

 ordinary circumstances have been sufficient. My first idea was 

 that there might be some local stoppage such as stones or air, 

 but an examination of the pipe revealed the fact that it was 

 choked up from the reservoir to the town by a deposit of peat 

 and iron oxide, which formed an annular ring about 1 inch 

 thick round the inside of the pipe. I therefore recommended 

 that the pipes be cleaned by scraping them with one of the 

 scrapers manufactured by the Glenfield Company, of Kilmar- 

 nock. This advice was adopted by the sanitary authority, and 

 I was ordered to proceed. My first operation was to get in 

 hatchboxes, three of which I inserted on the main. These 

 consist of a casting about 4 ft. 7 in. long, with spigot and faucet 

 ends, and a moveable cover secured by bolts to admit of the 

 insertion of the scraper. This latter consists of two pistons 

 kept apart by a hollow distance piece, in front of which is a 

 spindle on which are mounted a series of scraping blades. The 

 pistons are furnished with leather packing loaded with lead, 

 and fitting the main so as to prevent too much leakage, 

 which, if unchecked, would reduce the driving power, — a 

 great inconvenience in a small main. A little escape 

 is, however, necessary to wash away the deposit removed by 

 the knives in front. The knives are arranged in two sets. 

 They consist of a steel band terminating with the knife which 

 is curved and forked, and secured to the plate by bolts passing 

 through lugs in the web of each blade. The bar carrying the 

 scrapers is bolted up to the piston rod, which gives it a little 

 play going round curves. 



After inserting the hatchboxes and before beginning the 

 scraping, I carefully gauged the discharge of the pipe at its 

 entrance to the town, and found it to be 14*57 cubic feet per 

 minute. 



The scraping operations are simple, although in the case of a 

 pipe in which no provision has been made for such work they are 

 slow and troublesome. In the first operations the knives were set 



