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Helsel-Coating Lifetime Costs Final FOR COATING & INSPECTION
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Calculating Coating Lifetime Costs
Presented by:Jayson L. Helsel, P.E.
KTA-Tator, Inc.
Learning Outcomes
• Completion of this webinar will enable the participant to: Define various service environments Identify suitable coating systems for intended service Describe a typical maintenance painting sequence Calculate installed cost for coating systems Perform economic analysis Calculate coating lifetime cost
History• Based on “Expected Service Life and Cost
Considerations for Maintenance and New Construction Protective Coating Work,” presented at NACE Corrosion 2008
• Data from survey of contractors and coating manufacturers
• Data presented in SSPC Painting Manual Volume 1, Good Painting Practice, Chapter 10.2, “Comparative Painting Costs”
Coating System Data
• Commonly used coating systems For typical service environments
• Service life estimates Time until 5-10% coating breakdown For practical maintenance sequence
• Current material costs• Current shop painting costs• Current field painting costs
Coating Systems - Atmospheric
• Most common systems for atmospheric exposure
• Surface preparation requirementBlast cleaning or hand/power tool
cleaning
• Minimum dry film thickness• Service environments
Coating Systems - Atmospheric
• Service environments per ISO 12944-2, “Classification of Environments”C2: Low C3: Medium C5-I: Very High, Industry C5-M: Very High, Marine
Coating Systems - Atmospheric
• Service environment definition
C2: Low
“Atmospheres with low levels of pollution; mostly rural areas”
Coating Systems - Atmospheric• Service environment definition
C3: Medium“Urban and industrial atmospheres, moderate sulfur dioxide pollution; coastal areas with low salinity”
“Production rooms with high humidity and some air pollution (e.g., food processing plants, laundries, breweries, dairies)”
Coating Systems - Atmospheric• Service environment definition
C5-I: Very High, Industry
“Industrial areas with high humidity and aggressive atmosphere”
Coating Systems - Atmospheric
• Service environment definition
C5-M: Very High, Marine
“Coastal and offshore areas with high salinity”
Coating Systems - Immersion
• Most common systems for immersion service
• Surface preparation requirementAbrasive blast cleaning
• Minimum dry film thickness• Service environments
Coating Systems - Immersion
• Service environments Potable water Fresh waterSalt water
Hot Dip Galvanizing• Service life for 4 mils minimum
(American Galvanizers Association)Mild (rural) = 68 Years Moderate (industrial) = 33 Years Severe (heavy industrial) = 21 Years
Practical Service Life
• Time until 5 to 10% coating breakdown occurs (SSPC-Vis 2 Rust Grade 4)
• Active rusting of the substrate is evident
Rust Grade 4 & 5 – General Rusting
Rust Grade 4 & 5 – Spot Rusting
Rust Grade 4 & 5 – Pinpoint Rusting
Typical Maintenance Painting Sequence
• Original Painting• Spot Touch-Up and Repair• Maintenance Repaint
Spot prime and full overcoat
• Full RepaintTotal coating removal and replacement
Typical Maintenance Painting Sequence
• Spot Touch-Up and RepairThe first time coating repairs are made Intended to be completed at the
“Practical Life” (from Tables 1A or 1B)
Typical Maintenance Painting Sequence
• Maintenance RepaintEstimated to be the “Practical Life” plus
33% • e.g. “P” x 1.33
Typical Maintenance Painting Sequence
• Full RepaintExpected to occur at the year of
“Maintenance Repaint” plus 50% of the “Practical Life” • e.g. Maintenance Repaint year + [“P” x 0.5]
Maintenance Painting Example
• Service Environment: C3• Surface Preparation: Abrasive Blast
Cleaning• Coating system: 2 coat epoxy • “P” life = 12 years
Spot touch up @ 12 yearsMaintenance repaint @ 16 yearsFull repaint @ 22 years
Cost Data
• Current material costs• Current shop painting costs• Current field painting costs
Cost Data
• Current material costsDFTTheoretical cost per sq ftPractical sprayPractical brush/roller
Cost Data
• Current shop painting costsSurface prep cost per sq ftPaint application cost per sq ftHot dip galvanizing costCost multipliers
• Size of job• Member size for galvanizing
Cost Data
• Current field painting costsSurface prep cost per sq ftPaint application cost per sq ftCost multipliers
• Size of job• Complexity of structure• Existing conditions
Cost Comparisons
• Shop vs. FieldShop abrasive blast cleaning and
priming approximately half of field cost (minimum of 250 tons of steel)
Cost Comparisons
Cost Comparisons
Cost Comparisons • Shop applied inorganic zinc vs. hot
dipped galvanizing75,000 to 125,000 sq ft steelModerate service environment (C3)35 year structure life4% inflation & 7% interest
• Initial cost of galvanizing 43% greater• Life cycle cost for galvanizing 15%
less
Economic Analysis
• Net Future Value (NFV)How much will it cost, in inflated dollars
in the year scheduled?NFV = Current Cost [(1 + i)n]
i = inflation, n = years
Economic Analysis
• Net Present Value (NPV)The present worth of the inflated cost (in
monies today invested at current interest rates)
NPV = NFV (1/ [(1 + i)n] )i = interest, n = years
Economic Analysis
• For each coating system:Timing and number of painting
operationsCost of each painting operations Carry out for projected life of structure
Economic Analysis
• Present value analysisFor each painting operation calculate:
• Current cost• Net future value• Net present value
Present Value Analysis
Economic Analysis
• Average Equivalent Annual Cost (AEAC)Converts entire stream of present and
future costs to a present worth (NPV)Distributes that sum in equal annual
amounts over the structure’s lifeRepresents coating lifetime or life cycle cost
i = interest, n = structure life
Life Cycle Cost
Life Cycle Cost
Summary
• Coating system selectionSurface preparation and service
environmentDetermines “Practical” life
• Material costs• Shop or field preparation and
application• Economic analysis• Life cycle cost