Monitoring Environmental Conditions for Cleaning

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Monitoring Environmental Conditions for Cleaning
Painting Operations

• William D. Corbett
• KTA-Tator, Inc.

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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 Manufacturers PDS
• Location and Frequency of Data Acquisition
• Altering the Environment to Achieve Conformance

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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

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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)

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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

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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

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Converting Temperature

• Temperature expressed in Celsius or Fahrenheit
• Celsius
• Freezing is 0 boiling is 100
• Fahrenheit
• Freezing is 32 boiling is 212

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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

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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

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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 5F (3C) higher than the dew
  point temperature to preclude condensation
  (requirement may be invoked by specification)

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Significance of 5F (3C)

• Theoretically, a small (lt1F) increase (surface
  temperature over dew point) will preclude
  moisture formation
• Minimum increase of 5F (3C) compensates for
• Instrument tolerances
• Varying conditions
• Changing conditions

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Environmental Conditions for Coating Application

• Air Temperature (min. max.)
• Relative Humidity (min. or max)
• Dew Point Temperature
• Surface Temperature min. 5 F (3C) above Dew
  Point Temperature
• Wind Speed (max.)

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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

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Significance of Conditions, cont.

• Wind Speed
• Too windy can affect application (dry spray) and
  cause overspray damage
• Mixing/application of coatings under adverse
  weather conditions can void the manufacturers
  warranty and is considered a specification
  non-conformance

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History of Environmental Condition Measurement

• Whirling apparatus containing wet dry bulb
  thermometers developed in the 1600s

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Weve 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

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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
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Sling Psychrometer
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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

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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

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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)

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Determining Dew Point Temperature
Example Air temperature 60F Depression wet
bulb thermometer 5F Dew Point temperature 51F
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Determining Relative Humidity
Example Air temperature 60F Depression wet
bulb thermometer 5F Relative Humidity 73
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Relative Humidity and Dew Point Calculators

1. Convert oF to oC using right window
2. Align dry bulb wet bulb temperatures (top of
   calculator)
3. Read Dew Point from upper window
4. Align dry bulb dew point temperature (bottom of
   calculator)
5. Read RH from lower window

2, 3
1
4, 5
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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)

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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

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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

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Measuring Surface Temperature

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

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Assessing Wind Speed

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

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

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Calibration of Electronic Psychrometers

• Some manufacturers provide Calibration Kits
• Used to verify accuracy only
• Annual calibration by the manufacturer or
  approved laboratory recommended

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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

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Determining Conformance to Project Specifications

• Compare actual conditions to project
  specification requirements
• Example
• Air temperature 50-110oF
• Relative humidity lt 85
• Surface temperature 50-120oF and a minimum of
  5oF higher than dew point temperature
• Wind speed lt 15 mph

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Determining Conformance to Product Data Sheets

• Compare actual conditions to manufacturers
  recommendations
• Example
• Air temperature 35-110oF
• Relative humidity lt 95
• Surface temperature 35-120oF and a minimum of
  5oF higher than dew point temperature
• Wind speed Typically not addressed

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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

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Achieving Conditions by Changing the Environment

• Heat
• Dehumidification
• Humidification

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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

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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

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Dehumidification, cont.

• DH accomplished by
• Compression
• Refrigeration
• Desiccation (liquid or solid sorption)
• Combination of methods listed
• Refrigeration and desiccation (solid sorption)
  most common for field work

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Dehumidification, cont.

• 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
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Dehumidification, cont.

• 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
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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

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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
  manufacturers PDS
• Described the location and frequency of data
  acquisition
• Described three methods to altering the
  environment, in order to achieve conformance

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Monitoring Environmental Conditions for Cleaning
Painting Operations

• THE END