LRAD-COVERUn PAPER-INSULATED TELEPHONE CABLE 451 



To maintain a normal operating temperature, it is necessary to 

 remove 17,500 B.T.U.'s per minute. This is accomplished by cooling 

 the air which is re-circulated plus the fresh air taken into the system 

 to 72° F. 



The method of air distribution within the storage o\en was carefully 

 designed since the rate of regain of moisture by paper insulated cable 

 is dependent not only on the difference in vapor pressure of the cable 

 paper itself and that of the air passing over it but also on the velocity 

 of the air. The dry air is supplied through grill openings along the 

 side of the room at approximately 3-4 ft. from the floor, and at low 

 velocities consistent with positive circulation. Thus the driest air 

 is supplied at the point where it is most needed and, since the return 



Fig. 19 — Silica gel drying unit. 



ducts are located at the ceiling opposite to the grill openings, any 

 regain of moisture in the room itself is largely concentrated in air 

 strata above the cables. 



Operation of the Baltimore conditioning system (Fig. 19) may be 

 described briefly as follows: Approximately 10,300 cu. ft. of air per 

 minute from the storage room is mixed with 2600 cu. ft. per minute of 

 outside fresh air. The temperature of this air mixture which may be as 

 high as 100° F. is lowered to a maximum of 68° F. by passing it over 

 and around copper tubes through which water at 58-60° F. is circu- 

 lating. The cool air then passes through the first silica gel adsorber 

 where it is partially dehydrated; then it is again cooled and is passed 

 into the second adsorber where the drying is completed and from which 



