MIL-HDBK-1004/10

Rearranging the equation for n:

n = R /[R - (P p)/S]

v

n

s

n = 4.77/[2-(2,000p)/20]

n = 4.77/(2-100p)

Try n = 4 anodes,

p

=

0.00283 (refer to para. 6.2.1.4b)

4

=

4.77/(2-0283)

4

=

4.77/1.717

4

=

2.78 (not very close)

Try n = 3 anodes,

p

=

0.00289 (refer to para. 6.2.1.4b)

3

=

4.77/(2-0.289)

3

=

4.77/1.711

3

=

2.79

This is the closest possible.

In order to keep total resistance

below 2.0 ohms, use 3 anodes.

(4)

Actual resistance:

R

= (1/n)R

= P p/S

n

v

s

R

= (1/3)4.77 + 2,000 (0.00289)/20

3

R

= 1.59 + 0.29

3

R

= 1.87 ohms which is below 2.0

3

e)

Total weight of anodes for ground bed:

(1)

Weight of anode unit, 60 pounds (size 2 inches x 60

inches)

(2)

Total weight = 3 x 60 = 180 pounds

f)

Theoretical life of anode bed:

W = YSI/E

Rearranging gives

Y = WE/SI

182

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