Monitoring Environmental Conditions for Cleaning Painting Operations William

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

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

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

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)

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

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

Converting Temperature n Temperature expressed in Celsius or Fahrenheit n Celsius – Freezing is 0; boiling is 100 n Fahrenheit – Freezing is 32; boiling is 212

Converting Temperature n Converting Fahrenheit to Celsius Ø o. C = (o. F-32 o. F) ÷ 1. 8 n Example: Ø (83 o. F-32 o. F) ÷ 1. 8 = 28. 3 o. C n Converting Celsius to Fahrenheit Ø o. F = (1. 8 x o. C) + 32 o. F n Example: Ø (1. 8 x 5 o. C) + 32 o. F = 41 o. F

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

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)

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: Ø Instrument tolerances Ø Varying conditions Ø Changing conditions

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. )

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

Significance of Conditions, con’t. • Wind Speed Ø 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

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

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

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

Sling Psychrometer

Using Sling Psychrometers • ASTM E 337 • 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. 5 o) • Record wet & dry bulb temperatures

Using Battery-Powered Psychrometers • • ASTM E 337 Verify wick cleanliness Saturate wick Operate until wet bulb stabilizes (2 readings within 0. 5 o; typically 2 minutes) • Record wet & dry bulb temperatures

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)

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

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

Relative Humidity and Dew Point Calculators 1. 2. 3. 4. 5. Convert o. F to o. C 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

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)

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

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

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

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

Documenting Ambient Conditions and Surface Temperature Condition Data Date 2/23/11 Time 1300 hours Dry Bulb Temperature (DB) 16 o. C (60 o. F) Wet Bulb Temperature (WB) 13 o. C (55 o. F) Depression (DB-WB) Relative Humidity 3 o. C (5 o. F) 73% Dew Point Temperature 11 o. C (51 o. F) Surface Temperature 15 o. C (59 o. F) Wind Speed Measurement Location 11 km/Hr (7 mph) West side of tank, ground level

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

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

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

Determining Conformance to Project Specifications • Compare actual conditions to project specification requirements • Example: Ø Air temperature: 50 -110 o. F Ø Relative humidity: < 85% Ø Surface temperature: 50120 o. F and a minimum of 5 o. F higher than dew point temperature Ø Wind speed: < 15 mph

Determining Conformance to Product Data Sheets • Compare actual conditions to manufacturer’s recommendations • Example: Ø Air temperature: 35 -110 o. F Ø Relative humidity: < 95% Ø Surface temperature: 35120 o. F and a minimum of 5 o. F higher than dew point temperature Ø Wind speed: Typically not addressed

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

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

Achieving Conditions by Changing the Environment • Heat ØAchieve & maintain temperature during application & cure ØIndirect fired propane ØAC powered equipment with thermostatic controls ØVentilation to exhaust solvent vapors is critical

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-TR 3/NACE 6 A 192, “Dehumidification and Temperature Control During Surface Preparation, Application and Curing for Coatings/Linings of Steel Tanks, Vessels and other Enclosed Spaces”

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

Dehumidification, con’t. • Refrigeration Ø Air cooled over refrigeration coils Ø Condensation occurs on coils and is collected Ø Dry air exits the DH system (at reduced temperature, humidity and dew point) Source: SSPC-TR 3/NACE 6 A 192

Dehumidification, con’t. • Desiccant Ø Air passed over/through granular beds or fixed desiccant structures Ø Desiccant (silica gel or lithium chloride) is active and dehydrated (low vapor pressure) Ø Desiccant absorbs moisture from air. Hydration reaction causes exothermic reaction (heated air), so may be used with refrigerationtype DH Source: SSPC-TR 3/NACE 6 A 192

Achieving Conditions by Changing the Environment • Humidification ØMay be required for moisture coatings ØMoisture generated by wetting down floors or dampening the applied coating after initial drying

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

Monitoring Environmental Conditions for Cleaning & Painting Operations THE END