(6) Compute the minimum weight of riser anode material needed (eq C-1):

YSI

W'

,

E

where Y = 10 years, S = 1.0 pound per ampere-year, I = 3.62 amperes, and E = 0.50.

(10 yr)(1.0 lb/A&yr)(3.62A)

W'

,

0.50

W = 72.4 lb.

(7) Find the main anode circle's radius using equation D-8:

r = (DN)/2(B + N)

(eq D-8)

where D = 56 feet and N = 10 (assumed number of anodes). Thus,

56 ft 10

r'

2(3.1416 % 10)

r = 560/26.28

r = 21.3 ft, use 22 ft.

(8) Determine the spacing for the main anodes. Generally, the distance from the anode to the tank wall

and tank bottom is about equal; this distance should be about one-half the circumference between anodes.

(a) To find circumferential spacing, use equation D-9:

C = (2 B r) / N

(eq D-9)

where r = 22 feet (anode circle radius) and N = 10 (assumed number of anodes). Thus,

2 3.1416 22 ft

C'

10

C = 13.8 ft, use 14 ft.

(b) The cord spacing is approximately the same as circumferential spacing; 14 feet will be used (fig

D-8).