1118 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1953 



plied to all wires across the machine and permits a design in which the 

 current collecting brushes are always located on the same side of the 

 machine. 



When the wires leave acid copper plate cell No. 58, the full deposit of 

 copper has been applied. They pass into a dragout recovery cell where 

 they are washed by the makeup water, through an air wiper, and a water 

 wash cell before entering the heat treat section. The heat treatment has 

 two functions: First is to change the grain structure of the deposited 

 copper to an annealed form having small random cyrstals free of strain. 

 Second is to strain relieve the hard drawn steel core wire sufficiently to 

 increase its elongation to between 3 and 7 per cent. This is accomplished 

 by passing current through each wire to heat it to the necessary temper- 

 ature. The heat treated wire passes through a water wash cell which 

 serves as a quench and through a steam wiper which dries it in prepara- 

 tion for entering another turning section where it again changes direc- 

 tion 180° to enter the finish leg of the machine. 



The first solution that the wire enters at the finish leg is hydrofluo- 

 silicic acid which serves to remove any oxide which may have formed in 

 the heat treatment. This cleaning operation is performed in a single 

 koroseal covered cell. 



Four koroseal covered cells, three copper contact rolls and a koroseal 

 lined section of trough make up the lead plate section. The electrolyte is 

 lead fluosilicate. Lead sheets in the bottom of the cells are covered with 

 lead shot to form the active anode surface. 



The brass plating section applies the final deposit to the wire. Its func- 

 tion is to provide a coating which will unite chemically with the insula- 

 ting compound, giving good adhesion so that the load from the drop 

 wire clamps used to support the wire in service will not cause the insu- 

 lation to slip on the conductors. The composition of the deposited brass 

 is controlled between very close limits to obtain the desired adhesion 

 between conductor and insulating compound. The electrolyte contains 

 copper and zinc cyanide. There are four steel plating cells, three steel 

 contact rolls and a low carbon steel trough in the brass plate section. 

 The anode material is a mixture of copper and brass punchings which 

 rest directly on the steel cell bottoms. The finished wire is then wound 

 onto 660-pound reels. 



ELECTRICAL POWER 



Electrical power is purchased from the local utility company at 13.2 kv 

 and brought into the building by a pair of three-conductor, 300,000 

 circular mil, 15,000-voIt, lead-covered cables running in underground 



