Transcript Preparing a Coating Inspection Plan

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:
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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 requirement
Blast 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 requirement
Abrasive blast cleaning
• Minimum dry film thickness
• Service environments
Coating Systems Immersion
• Service environments
Potable water
Fresh water
Salt 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 Repaint
Total coating removal and replacement
Typical Maintenance
Painting Sequence
• Spot Touch-Up and Repair
The first time coating repairs are made
Intended to be completed at the “Practical
Life” (from Tables 1A or 1B)
Typical Maintenance
Painting Sequence
• Maintenance Repaint
Estimated to be the “Practical Life” plus 33%
• e.g. “P” x 1.33
Typical Maintenance
Painting Sequence
• Full Repaint
Expected 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 years
Maintenance repaint @ 16 years
Full repaint @ 22 years
Cost Data
• Current material costs
• Current shop painting costs
• Current field painting costs
Cost Data
• Current material costs
DFT
Theoretical cost per sq ft
Practical spray
Practical brush/roller
Cost Data
• Current shop painting costs
Surface prep cost per sq ft
Paint application cost per sq ft
Hot dip galvanizing cost
Cost multipliers
• Size of job
• Member size for galvanizing
Cost Data
• Current field painting costs
Surface prep cost per sq ft
Paint application cost per sq ft
Cost multipliers
• Size of job
• Complexity of structure
• Existing conditions
Cost Comparisons
• Shop vs. Field
Shop 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
galvanizing
75,000 to 125,000 sq ft steel
Moderate service environment (C3)
35 year structure life
4% 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 operations
Cost of each painting operations
Carry out for projected life of structure
Economic Analysis
• Present value analysis
For 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 life
Represents coating lifetime or life cycle cost
i = interest, n = structure life
Life Cycle Cost
Life Cycle Cost
Summary
• Coating system selection
Surface preparation and service environment
Determines “Practical” life
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Material costs
Shop or field preparation and application
Economic analysis
Life cycle cost