MIL-HDBK-1004/10
Conclusions and Recommendations. In addition to the economic
13.5.6
benefits of protection, addition factors such as safety, reliable operation,
loss of product, environmental pollution and regulation indicate that cathodic
protection should be installed.
13.6
Economic Analysis - Example 3
13.6.1
Objective. Install a steel (fuel) pipeline, using cathodic
protection, 8 inches in diameter and 15,000 feet long.
13.6.2
Alternatives
a)
Impressed current cathodic protection system
b)
Galvanic anode cathodic protection system
13.6.3
Assumptions
a) The soil resistivity is equal to 5,000 ohm-cm, pH 6, which is a
moderately aggressive corrosion environment.
b) The economic life of a fuel pipeline is 25 years. It is
assumed that no salvage value will be remitted in year 25 unless total
replacement is cost justified at that point in time.
c) The predicted number of leaks on a steel fuel line with
impressed current cathodic protection is zero. Continued protection and
maintenance is assumed. Repair of the rectifier is required every 10 years.
Replacement of the anodes is required every 20 years. This prediction is
based on historical data and technical expertise.
d) The predicted number of leaks on a steel fuel line with
galvanic anode cathodic protection is zero. Continued protection and
maintenance is assumed. A major rehabilitation of the system is required
every 15 years. This prediction is based on historical data and technical
expertise.
e)
To compute present values, a 10 percent discount rate is
assumed.
f) Costs of labor and materials rise (or lower) with the general
inflation rate. Cost of fuel, however, requires special treatment when
determining the value lost (disbenefit) from a pipeline leak. Otherwise, this
analysis requires no special treatment of inflation.
13.6.4
Cost/Benefit Analysis
13.6.4.1
Cost - Alternative 1--Impressed Current Cathodic Protection. Cost
of steel line with impressed current system - 8,000. Annual cost of
maintenance with impressed cathodic protection system - ,200. Cost to
repair rectifier every 10 years -
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,500. Cost to replace anodes every 20
years - ,000.
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