Page 217 - Pipeline Rules of Thumb Handbook

204 Pipeline Rules of Thumb Handbook

Figure 10. Number of anodes required for coated line protection.

Example. A coated pipeline has a coating conductivity of Source
100 micromhos/sqft and is 10,000ft long, and the diameter is Pipeline Corrosion and Cathodic Protection, Gulf Publishing
3
10 /4 -in. How many 17lb magnesium anodes will be required Company, Houston, Texas.
to protect 1,000ft? Refer to Figure 7 and read 2 anodes per
1,000ft. A total of twenty 17# anodes will be required for the Reference
entire line. 1. From data prepared for the American Zinc Institute.

Estimate the pounds of sacrificial anode material required for offshore pipelines

This rule of thumb is based on the following Basis for rule: sqft of surface area of pipeline/linear ft ¥ %
assumptions: of bare pipe ¥ 3.0 m.a./sqft ¥#/amp.-year ¥ design life in
years = the lb of galvanic anode material that will be required.
• 5% of pipeline considered bare
.-
¥
• 3 milliamperes/sqft required for protection Multiplier = OD lb amp yr ¥ (12 PI 144 )
0
1
0
• 30-year design life ¥ 30 ¥ .05 ¥ .003 ¥ ,000