460 



BELL SYSTEM TECHNICAL JOURNAL 



system. The down spouts are of seamless steel tubing and have a steel 

 valve at each joint with the main line and a service valve at one corner 

 of the "IT" bend. All joints are oxyacetylene welded, and no fittings 

 are used throughout the system. The lines are insulated with pipe 

 covering protected by a layer of fireproofed canvas (Fig. 28). 



The lines are heated initially by a series of transformers which 

 supply a low-tension, high-amperage current directly into the pipe 

 by forming a loop of the supply and return line. Once circulation of 

 the lead has been established in the piping system, the main line 

 requires little additional heat from the transformers, as the flow of the 



• -. '^^.•ci 





Fig. 28 — Main lead supply lines. 



lead will ordinarily keep the line up to temperature. Approximately 

 4 K\'A are required on each down spout while in use. The connections 

 leading from the transformer to the pipe are flexible, to allow for 

 expansion and contraction of the system. 



Switches are provided on each building column opposite the presses 

 to enable an operator to shut down the pumping system in case of a 

 serious leak or failure of a valve. 



This system has been in operation for about nine months and has 

 resulted in a higher quality of lead sheath due to more uniform compo- 

 sition maintained. In addition there are considerable savings in fuel, 

 reduction in dross, and elimination of a large amount of heavy manual 

 effort. The press room is now clean and cool, resulting in much better 

 working conditions and in turn an indirect improvement in the 

 quality of the product. 



