MIL-HDBK-1004/10

EQUATION:

R

=

0.012 P log (D/d)/L

(13)

where

R

=

anode-to-electrolyte resistance (ohms)

P

=

water resistivity (ohms-cm)

L

=

length of a single anode (feet) (backfill is not used)

D/d

=

ratio of anode diameter (d) to tank diameter (D)

(same units for each)

The anodes are usually arranged in a circular array in the tank bowl. The

optimum diameter of this array can be determined by the following formula:

EQUATION:

DN/2(B + N)

(14)

r

=

where

r

=

radius of anode array (feet)

D

=

tank diameter (feet)

N

=

number of anodes

If four or more anodes are used in a circular array, the following modified

Shepard formula should be used to calculate the resistance of the array:

EQUATION:

R

=

0.012 P log (D/a)/L

(15)

where

a

=

factor for equivalent diameter from table below,

multiplied by the optimum diameter of the anode circle

(calculated previously)

Number of

Factor for

Anodes

Equivalent

in Circle

Diameter

4

0.08

6

0.11

8

0.18

10

0.28

12

0.43

14

0.70

P

=

water resistivity (ohms-cm)

L

=

length of a single anode (feet)

D

=

tank diameter (feet)

Field Measurement. Calculations, as previously discussed, can give

6.2.1.5

good approximations of anode-to-electrolyte resistance under actual

conditions. While these calculations can be effectively used for system

design, if the environment is well known, the actual anode-to-electrolyte

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