LEAD-COVERED PAPER-INSULATED TELEPHONE CABLE 447 



cumference to the tank, and on the outer circumference to the brick 

 wall of the storage oven. 



Auxiliary equipment used with the vacuum drying ovens consists 

 of two welded vacuum lines (twelve inches in diameter) vacuum 

 pumps, condensers and receiver tanks. A general view can be obtained 

 from Fig. 16, 



Fig. 16 — ^Auxiliary equipment for vacuum driers. 



One vacuum line is used to establish vacuum in a new tank load of 

 cables, and the second is used for maintaining vacuum in the tanks 

 once they have reached the proper point. The pump equipment 

 consists of four reciprocating feather valve vacuum pumps. The 

 pistons on these pumps have a diameter of twenty-nine inches and a 

 stroke of eighteen inches or a displacement of ten hundred and twenty 

 five C.F.M. The pumping capacity has been based on maintaining 

 absolute pressures of one-half to one inch in the vacuum tanks. 

 These values are based on a vacuum tank activity of eighty-five per 

 cent and on maximum leakage of approximately twenty pounds of air 

 into each tank through the door gaskets. 



Two two hundred and twenty five C.F.M. surface condensers are 

 incorporated in the layout ahead of the pumps to condense moisture 

 given off by the insulated paper. Three thousand pounds of water 

 may be extracted in twenty-four hours. 



New features incorporated in the oven are design changes of the 

 heater coil and tank. This coil, of which there are four in each oven, 

 consists of steam header inlet and outlet, instead of a continuous 



