Title: Monitoring Environmental Conditions for Cleaning
1Monitoring Environmental Conditions for Cleaning
Painting Operations
- William D. Corbett
- KTA-Tator, Inc.
2Introduction
- 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
3Learning 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
4Definitions
- 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)
5Definitions
- 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
6Definitions
- 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
7Converting Temperature
- Temperature expressed in Celsius or Fahrenheit
- Celsius
- Freezing is 0 boiling is 100
- Fahrenheit
- Freezing is 32 boiling is 212
8Converting 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
9Environmental 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
10Measuring 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)
11Significance 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
12Environmental 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.)
13Significance 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
14Significance 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
15History of Environmental Condition Measurement
- Whirling apparatus containing wet dry bulb
thermometers developed in the 1600s
16Weve 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
17Ambient 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
18Sling Psychrometer
19Using 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
20Using 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
21Using 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)
22Determining Dew Point Temperature
Example Air temperature 60F Depression wet
bulb thermometer 5F Dew Point temperature 51F
23Determining Relative Humidity
Example Air temperature 60F Depression wet
bulb thermometer 5F Relative Humidity 73
24Relative 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
25Using 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)
26Electronic 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
27Electronic 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
28Measuring Surface Temperature
- Dial-Type Thermometer
- Position stabilize for minimum of 2 minutes
- Thermocouple-Type Thermometers
- Stabilize quickly
- Infrared (non-contact) thermometers
- Watch distance
29Assessing Wind Speed
- Analog wind meters
- Digital wind meters
- Rotating Vane Anemometers
- Air flow inside containment
- Wind speed
30Documenting 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
31Verification 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
32Calibration of Electronic Psychrometers
- Some manufacturers provide Calibration Kits
- Used to verify accuracy only
- Annual calibration by the manufacturer or
approved laboratory recommended
33Verification 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
34Determining 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
35Determining 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
36Location 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
37Achieving Conditions by Changing the Environment
- Heat
- Dehumidification
- Humidification
38Achieving 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
39Dehumidification
- 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
40Dehumidification, 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
41Dehumidification, 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
42Dehumidification, 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
43Achieving 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
44Summary
- 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
45Monitoring Environmental Conditions for Cleaning
Painting Operations