5 Jan 91
EXAMPLES OF IMPRESSED CURRENT
CATHODIC PROTECTION DESIGN
The following examples show the use of design procedures explained
in the previous section:
Steel fuel oil lines
Underground storage tanks
On-grade tank bottoms
Gas distribution systems
Elevated water tanks (ice is expected)
Elevated water tanks (no icing will occur)
On-grade water storage reservoir (ice is expected)
Steel Fuel Oil Lines.
Impressed current cathodic protection is desired for the 6-in.
welded fuel oil line shown in figures 2-1A and 2-lB. Since this
pipeline is in existence, current requirement tests have already
been made. There are no other underground structures in the area,
so a surface point groundbed is chosen. Figure 2-2 illustrates a
surface point groundbed anode system using prepackaged ceramic rod
anodes. These prepackaged ceramic rod anodes are further detailed
in figures 2-3 and 2-4.
a. Design data.
Pipe has 6-in. diameter
Pipe length is 6800 ft.
Design life for cathodic protection anodes is 15 years
since the structure will no longer be needed after that
Design current density is 2-mA per sq ft of bare pipe.
The pipe is coated with hot-applied coal-tar enamel.
90 percent coating efficiency based
experience with this type coating.