126 AXTOFAGASTA RAILWAY WATERWORKS. 



pipe laying to proceed in different sections at the same time, 

 expansion joints were employed in joining up the sections. 



The proposed route to Mejillones was eventually discarded, 

 and this main is now only worked as a low pressure main in 

 connnon with the rest of the pipe line. 



The Siloli iiiain line is laid with socket and spigot lapwelded 

 steel pipes of the following thicknesses: — 



Inches. Inches. 



The main has been in service for twelve years and has given 

 much less trouble than our ordinary cast iron mains. 



One extraordinary case of rapid corrosion occurred which 

 was somewhat disquieting, but a careful investigation of the 

 causes of this was made and definite conclusions arrived at, and 

 there has been no further trouble. The case of corrosion men- 

 tioned occurred at a joint, and, on examination, it was found 

 that the pipe had been eaten through, both on the socket and 

 through the part of the spigot where it left the socket. From the 

 appearance of the metal, it almost seemed as if the pipe had 

 fused. The pipe line at this point is laid in a bed of fine, hard 

 gravel. Due to faulty workmanship a portion of the lead joint 

 had blown out, and the issuing jet on the gravel had formed 

 a kind of circular sand blast which had eaten rapidly through 

 the steel. 



It is not quite certain how long this had been going on, but 

 the main had been in operation for only one year, and it is 

 possible that the leak from the joint had been going on for 

 that length of time. 



When designing the extension of the No. 2 main to Anto- 

 fagasta in 1910, advantage was taken of a short cut through the 

 hills to deviate from the railway line and save a distance of 17 

 miles. This, of course, was not possible with the first pipe line 

 which had to follow the route of the railway 'for purposes of supply 

 to the stations. 



In the last five miles of the route of the second pipe line, 

 there is a drop in level of 1,410 feet and it was felt that advantage 

 should be taken of this head to drive a Pelton wheel for the 

 generation of electric energy, which would be placed at the 

 inlet to the new reservoir which forms part of the scheme. 



The main was, therefore, designed with this object, and 11 

 inch lapwelded steel pipes with loose flanges and a thickness of 

 0-35 of an inch were laid down. It should be here noted that the 

 required discharge of the main to Antofagasta was only 3,500 

 cubic metres per day, but by the use of 11 inch pipes the maxi- 

 mum head available is made use of. Flat india-rubber rings in a 

 flat seating are used in making the joints between the flanges of 

 tlie pipes. 



