TM 5-811-7
a.
Design data.
(1) Tank diameter is 12 feet.
(2) Tank length is 40 feet.
(3) Design for 80 percent coating efficiency, based on experience.
(4) Design for 15-year life.
(5) Current requirement is 0.7 ampere.
(6) Packaged 17-pound standard magnesium anodes must be used.
(7) The tank is insulated well enough from foreign structures.
b. Computations.
(1) Find the minimum weight of anodes required for the tank using equation C-I:
YSI
W'
,
(eq C-1)
E
where Y = 15 years, S = 8.8 pounds per ampere-year, I = 0.7 ampere, and E = 0.50 efficiency. Thus,
(15 yr)(8.8 lb/A&yr)(0.7 A)
W'
,
0.50
W= 184.8 lb.
(2) Find the number of magnesium anodes (17 pounds each) required:
184.8
N'
' 10.9 (use 12 anodes for symmetry).
17
c.
Placement. Locate anodes as shown in figure C-2.
C-5.
Gas distribution system.
Galvanic cathodic protection is designed for a gas distribution system in a housing area as shown in figure
C-3.
C-5
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