POLYETIIYLKNE CABLE SHEATH THICKNESS 



575 



4c, 



•^ 





130 MO 150 160 170 180 190 200 



Fig. 14 — Recorder graph of single octant variation and thickness scale in 

 thousandths of an inch. 



feet per minute. It was found that the fluctuations or variation peaks of 

 one Une along the cable length could be averaged from chart lengths of 

 }/^ inch. Also that by taking measurements consecutively by octants 

 around the circumference a practical measure of the entire circumference 

 is obtained and is sufficient coverage to locate the minimum wall thick- 

 ness. The graphs of Fig. 15 show typical inspection recordings of two 

 cable lengths. 



Four thicknesses are specified for inspecting sheath, all of wliich are 

 obtained from a graph of the consecutively recorded octants. These 

 checks are: 



1. The minimum spot thickness. 



2. The average thickness lengthwise along the thinnest side. (Average 

 of minimum octant.) 



3. The average cross sectional thickness. (Average of octant averages). 



4. The maximum difference between the lengthwise average of the 

 thickest side (average of maximum octant) and the lengthwise 

 average of the thinnest side (average of minimum octant). 



