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Calculating Coating Lifetime Costs

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  1. Calculating Coating Lifetime Costs Presented by: Jayson L. Helsel, P.E. KTA-Tator, Inc.

  2. 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

  3. 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”

  4. 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

  5. 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

  6. 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

  7. Coating Systems - Atmospheric • Service environment definition • C2: Low“Atmospheres with low levels of pollution; mostly rural areas”

  8. 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)”

  9. Coating Systems - Atmospheric • Service environment definition • C5-I: Very High, Industry“Industrial areas with high humidity and aggressive atmosphere”

  10. Coating Systems - Atmospheric • Service environment definition • C5-M: Very High, Marine“Coastal and offshore areas with high salinity”

  11. Coating Systems - Immersion • Most common systems for immersion service • Surface preparation requirement • Abrasive blast cleaning • Minimum dry film thickness • Service environments

  12. Coating Systems - Immersion • Service environments • Potable water • Fresh water • Salt water

  13. 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

  14. Practical Service Life • Time until 5 to 10% coating breakdown occurs (SSPC-Vis 2 Rust Grade 4) • Active rusting of the substrate is evident

  15. Rust Grade 4 & 5 – General Rusting

  16. Rust Grade 4 & 5 – Spot Rusting

  17. Rust Grade 4 & 5 – Pinpoint Rusting

  18. 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

  19. 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)

  20. Typical Maintenance Painting Sequence • Maintenance Repaint • Estimated to be the “Practical Life” plus 33% • e.g. “P” x 1.33

  21. 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]

  22. 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

  23. Cost Data • Current material costs • Current shop painting costs • Current field painting costs

  24. Cost Data • Current material costs • DFT • Theoretical cost per sq ft • Practical spray • Practical brush/roller

  25. 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

  26. 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

  27. Cost Comparisons • Shop vs. Field • Shop abrasive blast cleaning and priming approximately half of field cost (minimum of 250 tons of steel)

  28. Cost Comparisons

  29. Cost Comparisons

  30. 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

  31. 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

  32. 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

  33. Economic Analysis • For each coating system: • Timing and number of painting operations • Cost of each painting operations • Carry out for projected life of structure

  34. Economic Analysis • Present value analysis • For each painting operation calculate: • Current cost • Net future value • Net present value

  35. Present Value Analysis

  36. 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

  37. Life Cycle Cost

  38. Life Cycle Cost

  39. Summary • Coating system selection • Surface preparation and service environment • Determines “Practical” life • Material costs • Shop or field preparation and application • Economic analysis • Life cycle cost