MIL-HDBK-1004/10
c) Number of anodes required. The low resistance (2.39 ohms) of a
single anode and the large weight of anode material required (1,032 pounds)
for a 15-year life indicate that the controlling factor is the amount of anode
material, not ground bed resistance. The minimum number of anodes required
is:
N = 1,032/25 = 41.3 or 41 anodes
These are arranged in a distributed ground bed as shown in Figure
111 based on the following estimates:
d)
Anode distribution:
(1)
Area of conduit in sections 1 through 6:
Length (ft)
Surface Area (ft)
Section
1
1,700
3,553
+
6,239
=
9,792
2
500
785
+
1,310
=
2,095
3
1,125
1,766
+
3,533
=
5,299
4
350
550
+
917
=
1,467
5
400
628
+
1,048
=
1,676
6
275
432
+
721
=
1,153
(2)
Area of conduit protected by one anode:
A = 21,482/41
A = 524 ft/anode
(3)
Division of anodes:
Section
1
-
9,792/524
= 19 anodes
Section
2
-
2,095/524
= 4 anodes
Section
3
-
5,299/524
= 10 anodes
Section
4
-
1,467/524
= 3 anodes
Section
5
-
1,676/524
= 3 anodes
Section
6
-
1,153/524
= 2 anodes
Rectifier Location. Locate the rectifier in front of the
9.8.4
administration building as shown in Figure 111. The rectifier is sized after
anodes are installed.
Aircraft Multiple Hydrant Refueling System. Galvanic cathodic
9.9
protection is designed for a standard aircraft hydrant refueling system as
shown in Figure 112. This design is for a system not yet installed.
9.9.1
Design Data
a)
Average soil resistivity is 5,000 ohm-cm.
b)
Design for 90 percent coating efficiency, based on experience.
c)
Design for 15-year life.
195
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