MIL-HDBK-1004/10
b) Paralleling of Anodes. Common practice to reduce anode bed
resistance is to connect several anodes in parallel in a group. The
resistance of a group of anodes is less than the resistance for a single anode
but is greater than that calculated from the usual parallel resistance formula
due to interactions between the fields surrounding each anode. If the anodes
are arranged in a parallel row, the resistance of a group of anodes can be
approximated by the following formula:
EQUATION:
R
=
(1/n)R
+ P F/S
(12)
n
v
s
where
Rn
=
total anode-to-electrolyte resistance for a group of
vertical anodes, equally spaced and in a single row, to
remote reference (ohms)
n
=
number of anodes
R
=
electrolyte-to-anode resistance for a single vertical
v
anode to remote reference (ohms)
P
=
electrolyte resistivity (ohms-cm) with pin spacing equal
s
to S
S
=
anode spacing (feet)
F
=
paralleling factor from table below:
F
n
F
n
2
0.00261
12
0.00182
3
0.00289
14
0.00168
4
0.00283
16
0.00155
5
0.00268
18
0.00145
6
0.00252
20
0.00135
7
0.00237
22
0.00128
8
0.00224
24
0.00121
9
0.00212
26
0.00114
10
0.00201
28
0.00109
30
0.00104
If multiple rows of anodes are used where the spacing between rows is more
than 4 times the spacing between the anodes in each row, the usual parallel
resistance formula:
1/R
=
1/R
+ 1/R
+ 1/R
+ 1/R
+ ...
may be used.
1
2
3
4
c) Special Formula for Water Tanks. For water tanks where
circular arrays of anodes are commonly used and where the structure surrounds
the anodes and electrolyte, special formulae have been developed to calculate
the anode-to-electrolyte resistance. For a single cylindrical anode, the
formula developed by E. R. Shepard may be used. The formula is as follows:
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