(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.
(1) Find the minimum weight of anodes required for the tank using equation C-I:
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= 184.8 lb.
(2) Find the number of magnesium anodes (17 pounds each) required:
' 10.9 (use 12 anodes for symmetry).
Placement. Locate anodes as shown in figure C-2.
Gas distribution system.
Galvanic cathodic protection is designed for a gas distribution system in a housing area as shown in figure