MIL-HDBK-1004/10
9.5.1
Design Data
a) Average soil resistivity, 4,500 ohm-cm.
b) Design for 90 percent coating efficiency, based on experience.
c) Design for 15-year life.
d) Design for 2 mA/ft of bare pipe.
e) Packaged type magnesium anodes must be used.
f) Insulating couplings are used on all service taps. The mains
are electrically isolated from all other metal structures in the area.
g) All pipe was precoated at the factory and wrapped with asbestos
felt. The coating was tested over the trench for holidays and defects
corrected. The coating is considered to be better than 99.5 percent perfect
at the time of installation.
9.5.2
a)
Total outside area of piping:
Pipe Size
Pipe Length
Pipe Area
Area of Pipe
(in.)
(ft)
(ft/lin ft)
(ft)
3
600
0.916
550
2
1,500
0.622
933
1-1/2
1,800
0.499
898
1
2,400
0.344
826
3/4
3,900
0.278
1,084
Total area of pipe in ft
4,292
b) Area of bare pipe to be cathodically protected based on 90
percent coating efficiency:
A = 4,292 x 0.1
A = 429 ft
c)
Maximum protective current required based on 2 mA/ft of bare
metal.
I = 2 x 429
I = 858 mA or 0.858 A
d) Weight of anode material required based on maximum current
requirement and 15-year life:
W = YSI/E
185
Previous Page
