Page 474 - Corrosion Engineering Principles and Practice

440 C h a p t e r 1 1 M a t e r i a l s S e l e c t i o n , Te s t i n g , a n d D e s i g n C o n s i d e r a t i o n s 441

• Requirements to be met
Properties (corrosion, mechanical, physical, appearance)
Fabrication (ability to be formed, welded, machined, etc.)
Compatibility with existing equipment
Maintainability
Specification coverage
Availability of design data
• Selection considerations
Expected total life of plant or process
Estimated service life of material
Reliability (safety and economic consequences of failure)
Availability and delivery time
Need for further testing
Material costs
Fabrication costs
Maintenance and inspection costs
Return on investment analysis
Comparison with other corrosion-control methods

TABLE 11.2 Material Selection Checklist

11.3.1 Life-Cycle Costing
Life-cycle costing utilizes universally accepted accounting practices
for determining the total cost of asset ownership or projects over the
service life. The economic analysis is usually performed for comparing
competing alternatives. Since the initial capital outlay, support, and
maintenance over the service life and disposal costs are considered,
the time value of money assumes major importance in life-cycle
costing. Discounting future cash flows to present values essentially
reduces all associated costs to a common point in time for objective
comparison.
Economic calculations used to be laborious procedures that could
only be properly performed by those who understood the
interrelationship of all the factors involved. Relatively good estimates
of initial costs, life, rate of depreciation, taxes, and value of money to
the owner/employer have been combined into easily used equations
in a NACE International standard that can be used without requiring
a great knowledge of economics [10]. This report advocates the use of
the discounted cash-flow method, which provides readily comparable