RESISTANCE OF MATERIALS TO MARIXE BIOLOGICAL ATTACK 1113 



860 

 840 

 820 

 800 

 780 

 760 

 740 

 720 



10 

 Q 

 < 



cr 

 < 



O 

 q: 

 u 



o 



cr 

 o 



2 700 



o 

 z 

 < 



o 



< 



u 



680 



660 



640 



620 



4 5 6 7 8 9 



TIME IN TEST IN MONTHS 



10 11 



12 13 



Fig. 6 — Capacitance changes resulting from exposure of GR-S (51-92) and 

 Poly (Vinyl Chloride) (BTL 172-54) insulated conductors in sea water and sediment. 



exposure — a total change of 218 \iiii. If it is assumed that the insulating 

 materials were removed equally along the length of the coil, it can be 

 computed that this change in capacitance represents a loss of 8.1 mils 

 of insulation. The following formula is used to arrive at this figure: 



D 



<W'" 



where D = present diameter in mils, 



Do = original diameter in mils, 



d = diameter of wire in mils, 



Co = original capacitance in ^tjuf (start of test), 



C = present capacitance in MMf- 



