MIL-HDBK-1004/10

Area in water = 20 x 40 x 7 = 5,600 ft

Area in mud = 20 x 25 x 7 = 3,500 ft

b)

Protective current required:

In water - 5,600 ft x 2 mA/ft = 11.2 A

In mud - 3,500 ft x 1 mA/ft = 3.5 A

Total = 14.7 A

c)

Minimum weight of anodes required for 10-year anode life:

W = YSI

where

W

=

weight of anodes required

Y

=

10 years

S

=

7.6 lbs/A yr (includes efficiency factor)

I

=

14.7 A current required

W

=

10 x 7.6 x 14.7 = 1,117.2 pounds

As there are 10 bents it is desirable for current distribution to have at

least one anode per bent. Thus, 120-pound anodes should be used if the

current output per anode is sufficient.

d)

Current output per anode:

Resistance of a single vertical anode (refer to para. 6.2.1.4)

R

= (P/L)K

V

where

R

= electrolyte-to-anode resistance

V

P = electrolyte resistivity

L = anode length

K = shape function

For A-120 anodes (refer to Table 22)

R

= 22/1(0.008) = 0.176 ohms

V

For A-120-1 anodes (refer to Table 22)

R

= 22/2(0.012) = 0.132 ohms

V

For A-120-2 anodes (refer to Table 22)

R

= 22/4(0.017) = 0.093 ohms

V

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