MIL-HDBK-1004/10
9.4.1
Design Data
a)
Average soil resistivity, 2,000 ohm-cm.
b)
Pipe size, 6-inch outside diameter.
c)
Pipe length, 6,800 feet.
d)
Design for 15-year life.
e)
Design for 2 mA/ft of bare pipe.
f)
Design for 90 percent coating efficiency, based on experience.
g) The pipeline must be isolated from the pumphouse with an
insulating joint on the main line inside the pumphouse.
h)
HSCBCI anodes must be used with carbonaceous backfill.
i) The pipe is coated with hot-applied coal-tar enamel and holiday
checked before installation.
j)
Anode bed must not exceed 2 ohms.
k) Electric power is available at 120/240 V ac, single phase, from
a nearby overhead distribution system.
9.4.2
a)
Outside area of gas main:
Pipe size - 6 inches (nominal)
Pipe length - 6,800 feet
Pipe area - 6,800 x 1.734 = 11,791 ft
b) Area of bare pipe to be cathodically protected based on 90
percent coating efficiency:
A = 11,791 x 0.1
A = 1,179 ft
c)
Protective current required based on 2 mA/ft of bare metal:
I = 1,179 x 2
I = 2,358 mA or 2.36 A
d)
Ground bed design:
(1) Anode size, 2-inch x 60-inch (backfilled 10-inch x
84-inch), spaced 20 feet apart.
180
Previous Page
