PULP INSULATION FOR TELEPHONE CABLES 



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insulation from unfurling. It was found that even the most flexible 

 pulp insulation so far produced, when impregnated with unmodified 

 paraffin would not withstand satisfactorily the handling incident to 

 splicing at low temperatures. A softer and more lubricating type of 

 compound is required and a suitable combination has been found by 

 adding paraffin oil to the paraffin wax. Different proportions of oil 

 and wax are used depending upon the temperature at the time of 

 installation and the compounding is done at the point of splicing. 

 At an atmospheric temperature of about 75° F. no oil is required and 

 below 10° F. about half oil and half wax makes a suitable compound 

 with proportionate amounts of oil for intermediate temperatures. 



40 35 30 25 20 15 



TEMPERATURE IN DEGREES FAHRENHEIT 



Fig. 10 — Curve showing effect of temperature on pull required to strip insulation 

 impregnated with various wax and oil mixtures. 



In starting to make a splice, the insulated conductors are brought 

 together in proper position, given a sharp crossover, the wires cut off 

 so as to give several inches of free end, the insulation broken at the 

 crossover and then stripped off the ends. Thus the ideal insulation is 

 one which when waxed, can readily be parted at the crossover and 

 when broken will slip freely along the wire, yet will withstand con- 

 siderable bending and folding at other places in the splice without 

 breaking. Pulp insulation tends to cling to the conductor somewhat 

 more than a paper tube of strip insulation and although there is con- 

 siderable variation in this characteristic in the product as now manu- 

 factured, it is sufficiently under control so that with a small amount of 

 experience a splicer applying his usual technique is able to handle 



