IX. — Operation of the Kennedy Pipe Scraper and Cause 

 OF Recent Failure — By F. W. W. Doane, M. Can. Soc. 

 C. E., City Engineer, Halifax, N. S. 



(Read January 11th, 1S94- ) 



On the inside of all water supply pipes which have been in use 

 for any length of time there will be found a heavy incrustation 

 of oxide of iron. This coating presents a very rough surface 

 compared with the original finish. It consists of large tubercles 

 or blisters which greatl}^ reduce the internal diameter, and con- 

 sequently the discharging powers of the pipes. 



In designing a system of water works, engineers give special 

 attention to two questions — cost and efficiency. The capacity 

 must be sufficient for all present requirements, and the probable 

 growing demands of the near future must not be overlooked. 

 The question of cost fixes a limit, however, and the water mains 

 are laid with sufficient capacity to deliver an adequate daily 

 suppl}^ with provision for estimated increase in population and 

 consumption during a stated period. The margin is not large, 

 consequently it becomes a serious matter when the diameter of 

 the pipes is reduced The domestic supply is unsatisfactory, the 

 pressure for fire purposes is insufficient, and unless the pipes can 

 be cleaned, expensive renewals and alterations in the system may 

 be necessary. 



The writer has been asked frequently if the oxidation on the 

 inner surface of a pipe would seriously affect its capacity. The 

 piece of three inch pipe exhibited to-night answers that question 

 beyond tlie shadow of a doubt. It was cut from the main on 

 Water Street, Halifax, near the Ordnance Yard. The original 

 diameter of three inches has been reduced to half an inch, and 

 as the capacity decreases in the ratio of the square of the diame- 

 ter, the effect on the discharging power is apparent. 



Lime has been deposited in the lakes for the purpose of pre- 

 venting the rapid formation of rust in the pipes, but though it 

 maj' retard the formation it does not prevent it. 



(445) 



