Monitoring Environmental Conditions for Cleaning & Painting Operations

1. Monitoring Environmental Conditions for Cleaning & Painting Operations William D. Corbett KTA-Tator, Inc.

2. Introduction • Webinar Content: • Overview of Commonly Monitored Conditions during Surface Preparation • Overview of Commonly Monitored Conditions during Coating Work • Instrumentation for Measuring Environmental Conditions • Documentation of Conditions • Determining Conformance to Project Specifications and/or Manufacturer’s PDS • Location and Frequency of Data Acquisition • Altering the Environment to Achieve Conformance

3. Learning Objectives/Outcomes • Completion of this webinar will enable the participant to: • Describe the environmental conditions commonly monitored during surface preparation and coating work • Describe the instrumentation that is commonly used to measure environmental conditions • Document environmental conditions • Compare on-site conditions to specification requirements • Describe the frequency and location of measurements • Describe methods for altering the environment to attain conforming conditions

4. Definitions • Air Temperature (Ta) • Wet Bulb Temperature (Tw) • Depression of Wet Bulb Temperature from Dry Bulb Temperature (Ta-Tw) • Relative Humidity (RH) • Dew Point Temperature (Td) • Surface Temperature (Ts)

5. Definitions • Air Temperature (Ta): Temperature of the surrounding air • Wet Bulb Temperature (Tw): A measurement of the latent heat loss caused by water evaporation from a wetted sock on the end of a bulb thermometer in a psychrometer • Depression of Wet Bulb Temperature from Dry Bulb Temperature (Ta-Tw): The calculated difference between the air temperature and the wet bulb temperature

6. Definitions • Relative Humidity (RH): The percentage of moisture or water vapor in the air, relative to the maximum attainable at the same temperature • Dew Point Temperature (Td): The temperature at which condensation of water vapor occurs on a surface • Surface Temperature (Ts): The temperature of the surface to be prepared and coated

7. Converting Temperature • Temperature expressed in Celsius or Fahrenheit • Celsius • Freezing is 0; boiling is 100 • Fahrenheit • Freezing is 32; boiling is 212

8. Converting Temperature • Converting Fahrenheit to Celsius • oC = (oF-32oF) ÷ 1.8 • Example: • (83oF-32oF) ÷ 1.8 = 28.3oC • Converting Celsius to Fahrenheit • oF = (1.8 x oC) + 32oF • Example: • (1.8 x 5oC) + 32oF = 41oF

9. Environmental Conditions for Surface Preparation • “Rough” surface preparation work can occur when conditions are less than desirable (unless prohibited by contract) • “Final” surface preparation work should occur when conditions preclude moisture formation on prepared surfaces

10. Measuring Ambient Conditions Prior to Final Surface Preparation • If air temperature and relative humidity are such that moisture from the air condenses on the surface, the surface may rust bloom, or rust back prior to coating • Recommend verifying that the temperature of the surface is at least 5°F (3°C) higher than the dew point temperature to preclude condensation (requirement may be invoked by specification)

11. Significance of 5°F (3°C) • Theoretically, a small (<1°F) increase (surface temperature over dew point) will preclude moisture formation • Minimum increase of 5°F (3°C) compensates for: • Instrument tolerances • Varying conditions • Changing conditions

12. Environmental Conditions for Coating Application • Air Temperature (min. & max.) • Relative Humidity (min. or max) • Dew Point Temperature • Surface Temperature [min. 5 °F (3°C)] above Dew Point Temperature • Wind Speed (max.)

13. Significance of Conditions • Air Temperature • Too cold or too hot can affect coating application & curing • Relative Humidity • Too damp or too dry can affect coating application & curing • Surface Temperature • Too cold or too hot can affect application & curing • Surface temperature at or below dew point temperature will result in condensation

14. Significance of Conditions, con’t. • Wind Speed • Too windy can affect application (dry spray) and cause overspray damage • Mixing/application of coatings under adverse weather conditions can void the manufacturer’s warranty and is considered a specification non-conformance

15. History of Environmental Condition Measurement • Whirling apparatus containing wet & dry bulb thermometers developed in the 1600’s

16. We’ve Come A Long Way Baby! • Use of Sling psychrometers to obtain dry bulb/wet bulb measurements is still mainstream • Electronic measurement is possible • Some electronic psychrometers adversely affected by “outdoor” conditions

17. Ambient Conditions & Surface Temperature • Measuring Instruments • Sling Psychrometers* • Battery-powered Psychrometers* • Electronic Psychrometers • Analog, Thermocouple-type & Non-contact Surface Thermometers * Used in conjunction with psychrometric charts or calculators

18. Sling Psychrometer

19. Using Sling Psychrometers • ASTM E337 • Verify wick cleanliness • Saturate wick and/or fill reservoir with DI water • Whirl 20-30 second intervals until wet bulb stabilizes (2 readings within 0.5o) • Record wet & dry bulb temperatures

20. Using Battery-Powered Psychrometers • ASTM E337 • Verify wick cleanliness • Saturate wick • Operate until wet bulb stabilizes (2 readings within 0.5o; typically 2 minutes) • Record wet & dry bulb temperatures

21. Using Psychrometric Charts • Locate Chart (relative humidity or dew point) • Verify Barometric Pressure (e.g., 30.0 in.) • Intersect air temperature with wet bulb depression (Ta-Tw)

22. Determining Dew Point Temperature Example: Air temperature: 60°F Depression wet bulb thermometer: 5°F Dew Point temperature: 51°F

23. Determining Relative Humidity Example: Air temperature: 60°F Depression wet bulb thermometer: 5°F Relative Humidity: 73%

24. Relative Humidity and Dew Point Calculators • Convert oF to oC using right “window” • Align dry bulb & wet bulb temperatures (top of calculator) • Read Dew Point from upper “window” • Align dry bulb & dew point temperature (bottom of calculator) • Read %RH from lower “window” 2, 3 1 4, 5

25. Using the Psychrometer Slide Scale • Intersect air temperature and wet bulb temperature • Base of “Y” points to relative humidity • Cannot determine dew point temperature • White ink fades over time/usage (left image)

26. Electronic Psychrometers • Measure/Record: • Air Temperature • Surface Temperature (ST) • Relative Humidity • Dew Point Temperature (DP) • Spread between DP and ST • Features • Auto-logging allows for automatic data collection • Magnetic surface probe • Data graphing and uploading using software • Audio/visual alarm

27. Electronic Psychrometers • Measure/Record: • Air Temperature • Surface Temperature (ST) • Relative Humidity • Dew Point Temperature (DP) • Spread between DP and ST • Features • Auto-logging • Integral magnets • Data uploading using software • Audio/visual alarm • BlueTooth® Data Output • Another model (right) offers infrared surface temperature

28. Measuring Surface Temperature • Dial-Type Thermometer • Position & stabilize for minimum of 2 minutes • Thermocouple-Type Thermometers • Stabilize quickly • Infrared (non-contact) thermometers • Watch distance

29. Assessing Wind Speed • Analog wind meters • Digital wind meters • Rotating Vane Anemometers • Air flow inside containment • Wind speed

30. Documenting Ambient Conditions and Surface Temperature

31. Verification of Accuracy - Thermometers • ASTM E 337 • Remove wick from thermometer • Compare dry & wet bulb temperatures quarterly • Compare thermometers to a traceable thermometer in controlled environment at minimum of 4 temperatures annually

32. Calibration of Electronic Psychrometers • Some manufacturers provide “Calibration Kits” • Used to verify accuracy only • Annual calibration by the manufacturer or approved laboratory recommended

33. Verification of Accuracy – Surface Thermometers • No “Standard” method • Equipment manufacturers provide instruction • Surface probes integral to electronic psychrometers are calibrated by the manufacturer • Compare thermometers to “Traceable” thermometer in controlled environment

34. Determining Conformance to Project Specifications • Compare actual conditions to project specification requirements • Example: • Air temperature: 50-110oF • Relative humidity: < 85% • Surface temperature: 50-120oF and a minimum of 5oF higher than dew point temperature • Wind speed: < 15 mph

35. Determining Conformance to Product Data Sheets • Compare actual conditions to manufacturer’s recommendations • Example: • Air temperature: 35-110oF • Relative humidity: < 95% • Surface temperature: 35-120oF and a minimum of 5oF higher than dew point temperature • Wind speed: Typically not addressed

36. Location and Frequency of Data Acquisition • Location • Dictated by where the work is being performed (e.g., inside vs. outside of a containment; balcony of elevated storage tank vs. ground level) • If interior, with ventilation in operation • Shops: Blast or Paint bay area • Frequency • Prior to final surface preparation • Prior to mixing of coatings • Four-hour data collection intervals is common • More frequent measurement if conditions are changing

37. Achieving Conditions by Changing the Environment • Heat • Dehumidification • Humidification

38. Achieving Conditions by Changing the Environment • Heat • Achieve & maintain temperature during application & cure • Indirect fired propane • AC powered equipment with thermostatic controls • Ventilation to exhaust solvent vapors is critical

39. Dehumidification • Dehumidification (DH) equipment removes air moisture, reducing opportunity for condensation • Conditions monitored using computer software (component to DH equipment) or by manual measurements • SSPC/NACE Joint Technical Report • SSPC-TR3/NACE 6A192, “Dehumidification and Temperature Control During Surface Preparation, Application and Curing for Coatings/Linings of Steel Tanks, Vessels and other Enclosed Spaces”

40. Dehumidification, con’t. • DH accomplished by: • Compression • Refrigeration • Desiccation (liquid or solid sorption) • Combination of methods listed • Refrigeration and desiccation (solid sorption) most common for field work

41. Dehumidification, con’t. • Refrigeration • Air cooled over refrigeration coils • Condensation occurs on coils and is collected • Dry air exits the DH system (at reduced temperature, humidity and dew point) Source: SSPC-TR3/NACE 6A192

42. Dehumidification, con’t. • Desiccant • Air passed over/through granular beds or fixed desiccant structures • Desiccant (silica gel or lithium chloride) is active and dehydrated (low vapor pressure) • Desiccant absorbs moisture from air. Hydration reaction causes exothermic reaction (heated air), so may be used with refrigeration-type DH Source: SSPC-TR3/NACE 6A192

43. Achieving Conditions by Changing the Environment • Humidification • May be required for moisture cure coatings • Moisture generated by wetting down floors or dampening the applied coating after initial drying

44. Summary • During this webinar, we have: • Reviewed commonly monitored conditions during surface preparation and coating work • Described the instrumentation used to measure environmental conditions, including methods of calibration and accuracy verification • Illustrated documentation procedures • Described the importance of determining conformance to project specifications and/or manufacturer’s PDS • Described the location and frequency of data acquisition • Described three methods to altering the environment, in order to achieve conformance

45. Monitoring Environmental Conditions for Cleaning & Painting Operations THE END