MIL-HDBK-1004/10
where
R
= electrolyte-to-anode resistance
V
P = electrolyte resistivity
L = anode length
K = shape function
For 2- by 60-inch anodes:
R
= 22/5(0.0234) = 0.103 ohms
V
c)
Weight of anodes required:
W = YSI
where
W
=
weight of anodes required
Y
=
10 years
S
=
1 lbs/A yr (includes efficiency factor)
I
=
14.7 A current required
W
=
10 x 1 x 14.7 = 147 pounds
Each 2- by 60-inch anode weighs 44 pounds, thus ten anodes would
have a life significantly longer than 10 years.
d)
Resistance of dc circuit:
The resistance for ten widely spaced anodes is
1/R = 1/0.103 + 1/0.103 + 1/0.103 + 1/0.103 + 1/0.103 + 1/0.103 + 1/0.103
1/0.103 + 1/0.103 + 1/0.103
R = 0.010 ohms
Resistance of feeder conductor:
200 feet of HMWPE Size #4 (0.254
ohms per M feet) (refer to Table 10):
R = 0.254 x 0.2 = 0.05 ohms
e)
Sizing of rectifier:
Requirements:
dc current - 14.7 A
Anode circuit resistance - (0.01 + 0.05) = 0.06
dc voltage = IR+3 = (14.7 x 0.06) +3 = 3.882 (say 4)
A standard rectifier in this range has an output of 18 A at 4 V. Figure 88
shows a typical installation of impressed current anodes on a pier structure.
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