TM 5-811-7
(9) Select the main anodes.
(a) The anode unit size chosen is 1c-inch outside diameter, -inch inside diameter, and 9 inches
long. This is a standard sausage-type anode that weighs 1 pound and has a surface area of 0.25 square foot.
(b) The minimum number of anode units per anode string (N), based on a required weight of 304
pounds and 10 anode strings, is computed as follows:
N = 304/(10 x 1)
N = 30.4, use 31 units per string.
(c) Because the inside tank surfaces are uncoated, a maximum structure-to-electrolyte voltage is not
a limiting factor. However, because it is desired to hold the anode current at or below the manufacturer's
recommended discharge rate of 0.025 ampere per anode for this type anode, the minimum number of anodes
will be--
15.2 A
' 60.8 (use 61 anodes per string.)
10 0.025 A
This number is not practical for the bowl since the distance between the anode hanger and tank bottom is only
28 feet. Table D-5 shows the maximum recommended current discharge per anode for various types of
anodes to insure a 10-year minimum life. Using a type B anode, three anodes per string are required. The
manufacturer does not recommend more than two type B anodes per string assembly because the strings are
fragile. Therefore, the best choice of anode for the main anode strings is type C or CDD. Type CDD is
recommended because the lead wire connection is protected longer by the thicker wall of the enlarged ends.
Two type CDD anodes per string provide a current capacity of 2 amperes 10 strings = 20 amperes. These
anodes are spaced as shown in figure D-9.
Table D-.5. Technical data--commonly used HSCBCI anodes
Anode max
Max current
Anode
Weight
discharge
Area
density
type
Size (in.)
(1b)
(A)
(sq ft)
(A/sq ft)
1c OD x 9
a
FW
1
0.025
0.2
0.1
b
FC
1 x 9
4
0.075
0.3
0.25
G-2
2 OD x 9
5
0.100
0.4
0.25
G-2
2 x 9
9
0.20
0.5
0.40
Bc,d
1 x 60
12
0.50
1.4
0.36
C
1 x 60
25
1.00
2.0
0.50
c
CDD
1 x 60
26
1.00
2.0
0.50
c
M
2 x 60
60
2.5
2.8
0.9
SM
4 x 60
20
10.0
5.5
1.8
K-6
6 x 2
16
0.225
0.5
0.45
7
K-12
12 x 3 /16
53
0.80
1.0
0.80
B-30
1 x 30
7
0.25
0.7
0.36
1
TA-2
2 /16 x 84
46
6.4
4.0
1.6
a
For elevated freshwater tank.
b
For distributed system in ground trench.
c
Each end enlarged with cored opening for wire.
d
Not more than two anodes per assembly.
U.S. Air Force.
D-16
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