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Monitoring Environmental Conditions for Cleaning

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Use of Sling psychrometers to obtain dry bulb/wet bulb measurements is still mainstream ... Thermometers Calibration of Electronic Psychrometers Verification ... – PowerPoint PPT presentation

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Title: Monitoring Environmental Conditions for Cleaning


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

11
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

12
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.)

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, 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

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

16
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

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 60F Depression wet
bulb thermometer 5F Dew Point temperature 51F
23
Determining Relative Humidity
Example Air temperature 60F Depression wet
bulb thermometer 5F Relative Humidity 73
24
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
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
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
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 lt 85
  • Surface temperature 50-120oF and a minimum of
    5oF higher than dew point temperature
  • Wind speed lt 15 mph

35
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

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, 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

41
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
42
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
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
    manufacturers 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
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