Thermography is widely used to detect defective
connections for supply/return conductors within electrical
distribution systems. Thermography can also be used to detect
loose/deteriorated connections within bonding and grounding
systems.
In a perfect world, substation structures
and protective fencing surrounding the sub would never become
energized. In the REAL world, substation structures and nearby
metal components can, and often do, become energized either
by leakage current or induction. For safety, all structures
near and within the substation are electrically bonded together
and wired directly to ground in order to carry this unwanted
and potentially lethal power to ground.
Because grounding systems frequently carry
current, loose or deteriorated connections will often manifest
themselves as hot spots at or near the source of the problem.
Because a loose grounding conductor can compromise the integrity
of the grounding/bonding system, any inexplicable hot spots
should be investigated as soon as possible regardless of
temperature rise.
It is recommended that hot spots within
a grounding system should be given top priority. Should a
grounding connection fail, anyone making contact with the
energized portion of the structure could be seriously or
fatally injured.
A follow up inspection should be performed
once any repairs have been made to ensure that the subject
repairs were effective.
January
12, 2004
Sponsored
by:
Truth, Thermography
and the World Wide Web
“Stretchers”, “tall tales” and “selective
interpretation of the truth” are politically correct
terms that apply to statements that are misleading or false.
With no editorial controls, the world wide web is rife with
deceptive claims. Because thermography is not immune to inaccurate
web postings, thermographers should be cautious in their
acceptance of material posted on the web.
Prudent web surfers frequently view material on the internet with a healthy
amount of skepticism. All too frequently, the amount of caution is inversely
proportional to value of the product being advertised. Further compounding
the problem are unscrupulous advertisers who publish misleading information.
Some current examples include:
Brochures for thermal imagers containing
images taken with a different model imager
Publication of specifications that are
incomplete or inaccurate
Literature and trade names suggesting
imager models for inappropriate applications
Obsolete imagers renamed and offered
as current models, although manufacturer support is no
longer available
For equipment purchases, the above are often
exacerbated when the reader is untrained and/or inexperienced
with the technology. Before purchasing a thermal imager,
be sure to try the subject equipment under the exact conditions
you will encounter in the workplace.
When it comes to the internet, the
old adage, “You can’t always believe everything
you read” is frequently sage advice.
January
26, 2004
Sponsored
by:
Infrared Imaging
and Mold Detection
As concerns regarding indoor air quality
increase, there is increasing concern with respect to mold.
Used properly, a thermal imager can help identify areas of
potential mold growth.
Mold is a ubiquitous single cell organism
that tends to favor moist environments. Of the thousand species
of mold found worldwide, many are harmless; however, certain
species are toxic. Others can cause chronic health problems
in humans.
While thermal imagers cannot detect mold
directly, they can often detect evidence of the latent moisture
often associated with mold presence. When using a thermal
imager to detect latent moisture, keep the following in mind:
Evidence of moisture can only be detected
if a temperature differential exists across the surface
of the material being inspected.
Frequently, a delta T can be created
by actively heating or cooling a structure or by relying
on solar loading of the subject areas.
Subject building components should be
imaged from both indoor and outdoor aspects under the correct
weather conditions.
Suspected moisture presence must be confirmed
by independent means.
A negative finding for latent moisture
does not guarantee that mold is not present.
Since moisture presence is not positive
proof of mold presence, further laboratory tests will be
required to confirm mold within any moist areas detected.
February
2, 2004
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by:
Scheduling IR
Equipment for Maintenance
Many thermographers think of the holidays
as a time for family, festivities and annual maintenance
of their infrared equipment. Planning ahead can help to minimize
imager downtime and avoid or minimize program interruption.
Because infrared test equipment plays a
key role in an inspection program, minimizing downtime required
for service is imperative. Keeping the following in mind
can help routine service to proceed more smoothly and ensure
a faster turnaround for your imager.
Schedule routine equipment service
and/or calibrations well in advance
Most service departments require you to obtain a Return Authorization
before shipping equipment
Be sure to include all optics and filters when shipping your system
Consider scheduling service before
or after holidays to avoid service backlogs
Arrange for replacement equipment
if you anticipate a long delivery time for service
When shipping your equipment, enclose
a letter stating services required and any problems with
the subject equipment. Be sure to affix a Packing List
to the exterior of your shipping container noting descriptions
and serial numbers of items shipped. Lastly, don’t
forget to ascertain Customs requirements if your equipment
must be shipped outside of your country for service.
February
9, 2004
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by:
An Emittance
Greater Than 1.0 ?
According to the laws of physics, only a
perfect blackbody may have Emittance of 1.0. Although the
E value of real objects must be less than 1.0, some radiometers
allow entry of E values exceeding 1.0. The following describes
how these radiometers achieve the impossible.
Emittance is a measure of how well an object
radiates energy when compared to a blackbody at the same
wavelength and temperature. Emittance for any object is measured
on a scale between 0 and 1.0. Since blackbodies (E=1.0) exist
only in theory, real world objects will have E values of
less than 1.0. The E value of an object can never exceed
1.0.
Assuming that most objects are opaque (T=0),
they must be somewhat reflective. When making an infrared
temperature measurement, this reflected energy represents
an error source. To overcome errors due to reflections, quality
radiometers have inputs for reflected temperature. By measuring
reflected temperature and entering this value into the radiometer’s
computer, this error source is compensated for in the radiometer’s
software.
Less sophisticated radiometers often
lack inputs for reflected temperature. To compensate for
this, these radiometers allow the user to exceed E values
of 1.0. Although this overcompensation may allow the user
to match a desired reference temperature, it can lead to
significant errors. For infrared temperature measurement,
the best solution is to use quality radiometric equipment
and eliminate or avoid reflections whenever possible.
February
16, 2004
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by:
Tips for Battery
Care
Overlooked and underappreciated until they
fail, batteries supply the lifeblood of portable test equipment.
Proper care of rechargeable batteries can extend service
life and maximize run time.
Current choices in rechargeable battery
types sound like a recipe for alphabet soup: NiCd, NiMH,
and Li-Ion. Advancements in technology have made portable
batteries more reliable while reducing required care. Safely
obtaining optimum battery performance and longevity is easy
if you observe the following:
Never use batteries for anything other
than intended use
Discharge batteries fully before recharging
Charge batteries only with the appropriate
charger in a well-ventilated area
Disconnect batteries from charger when
charging is complete
Assign batteries to a specific charger
to allow for easier troubleshooting should charger fail
Inspect charger cables and connections
for cleanliness and integrity on a regular basis
Periodically exercise batteries by discharging
and recharging
Lastly, batteries are not immortal. Following
the above can help to extend battery life; however, one should
plan to replace rechargeable batteries at regular intervals
or when run times shorten appreciably. Always dispose of
defective batteries properly and recycle whenever possible.
February
23, 2004
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by:
Infrared Roof
Inspections From Indoors?
Infrared inspections of flat roofs are a
time-tested procedure for detecting evidence of subsurface
moisture within a roofing system. Current standards specify
infrared inspections be performed from the exterior of the
building; however, infrared inspections may be performed
from the interior of the building under certain conditions.
Thermography is a dynamic technology. New
applications are constantly being developed and existing
methodologies are constantly being improved. As an alternative
to imaging from the exterior of the building, some have suggested
inspecting the underside of the roof deck from the interior
of the building
When selecting a vantage point for an infrared
roof inspection, the most important consideration is roof
construction. Commerical roofs constructed with relatively
thin decks and no air spaces between system components may
be inspected from either indoors or outdoors.
Prior to tackling an infrared roof inspection
from the interior of the building, the following conditions
must be met.
Roof surface should be clean and dry
Line of sight access to subject roof
areas is required
Space beneath the roof deck should be
uniform temperature
Viewing locations should be selected
to eliminate interference from hot or cold objects such
as HID lanps and HVAC equipment
Lastly, inspection must be timed to
ensure adequate delta T exists between wet and dry insulation.
Upon completion of infrared inspection, all data should
be veirified by invasive testing.
March
1, 2004
Sponsored
by:
Remote Monitor
for Any Imager
When performing infrared inspections in
hazardous or hard-to-reach areas, a remote monitor screen
can be a valuable accessory. Combining an after-market LCD
monitor or camcorder equipped with a monitor screen can provide
a cost effective solution for expanding the functionality
of your imager while increasing safety.
Thermal imagers with monocular viewfinders
require a thermographer to stand in front of the object being
inspected. This requirement can compromise safety by exposing
a thermographer to hazardous or high temperature objects.
Several modern thermal imagers offer remote
monitor screens as either a standard feature or as an accessory.
Traditionally, LCD monitors available from imager manufacturers
have been expensive. As a result of technological advancements,
a wide array of LCD monitors are now available at affordable
prices.
Since many thermal imagers have video output
jacks, it is possible to connect an external LCD using a
standard video cable. When selecting an external monitor,
keep the following in mind.
Ensure imager video output is compatible
with the chosen monitor
Consult monitor specs to confirm suitability
for chosen environment
Use high quality cables to reduce signal
loss
· Beware of tripping hazards that
can be caused by onnecting cables
Lastly, choose a monitor with sufficient
resolution, brightness and contrast to provide a quality
image.
March
8, 2004
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by:
Potentially
Lethal Hot Spots
Thermography is a proven technology for
finding many types of defects within electrical systems.
While infrared inspections can assist in PdM efforts, they
can also point out a potentially lethal condition that can
lead to electrocution and death.
Many AC electrical devices are wired with
a grounding conductor. Ungrounded metallic structures and
devices can become unintentionally energized if a bare circuit
conductor makes contact with the subject structure. In ungrounded
structures, improper wiring or defective/deteriorated insulation
can allow the structure to become energized up to full circuit
voltage. In such cases, anyone touching the energized structure
may be electrocuted or fatally injured. One such fatality
occurred in May, 2003 when a nine year-old boy made contact
with an energized light pole in Columbus, Ohio.
On at least three separate occasions in
2003, thermographers have found evidence of energized structures
with a thermal imager. All three findings involved outdoor
metal light poles which exhibited inexplicable hotspots where
the pole was bolted to the concrete footing. In the Columbus
case, a nearby steel fence post also exhibited an inexplicably
hot base where bolted to the concrete sidewalk.
For reference we have included thermal
images of one of the aforementioned light poles. We urge
thermographers to be on the lookout for this potentially
lethal thermal anomaly and to immediately notify appropriate
personnel should you detect evidence of this condition
in the future.
Thermal images show base of metallic
light pole operating in excess of 180ºF due to ground
fault condition.
March
15, 2004
Sponsored
by:
Point Radiometers & Spot
Measurement Size
With awareness of infrared technology at
an all time high, point radiometers have become a common
tool in many areas. Frequently, knowledge of proper operation
lags behind instrument popularity. Understanding how spot
measurement size affects accuracy is imperative to collecting
meaningful data.
All radiometers are limited by a characteristic
known as spot measurement size or spot size, for short. Spot
size is determined by a radiometer’s detector and optics.
Typically, spot size increases as distance to the target
is increased. For accurate temperature measurement, spot
size must always be smaller than the target being measured.
When using a point radiometer, be sure to keep the following
in mind:
Point radiometers are usually supplied
with a Distance to Spot Ratio value. To determine spot
size, divide distance to target by ratio value.
Point radiometers have minimum focus
distances. At lesser distances, spot size will not decrease.
Single, laser-generated aiming dots
do not represent spot size
Multiple, laser-generated aiming circles/dots
often understate spot size
Beware of stated spot size ratio values.
Spot size ratios are frequently quoted at 90% radiance
(accuracy) or less
When using a point radiometer, be
sure to understand the limits of your instrument and the
challenges presented by your target. Always use correct
emissivity values and stay within the limits of your instrument.
March
22, 2004
Sponsored
by:
Temperature
Rise as a Severity Indicator
For years, many thermographers have sought
to qualify the severity of detected exceptions by measuring
temperature rise. Although this technique is widely practiced,
failure to understand key issues can lead to misdiagnoses
and unplanned downtime.
For over 25 years, thermographers have frequently
attempted to qualify the severity of detected exceptions
by comparing the temperature of the exception to similar
components under similar load or to ambient air temperature.
Although qualifying exception severity may be desirable for
maintenance planning, it also involves a certain degree of
risk management as some exceptions may rapidly deteriorate
and lead to an unplanned outage.
To better understand the risks associated
with assigning severity to exceptions based upon temperature,
it is important to keep the following in mind:
For highly reflective targets, small
emissivity errors can cause significant infrared temperature
measurement errors
Infrared temperatures are subject to
errors due to spot measurement size
The source of an exception may be contained
within a device prohibiting direct measurement at the point
of origin
IR temperature measurement is subject
to significant errors due to atmospheric conditions such
as wind, solar gain and moisture
The temperature of electrical exceptions
can increase dramatically and without warning if arcing
should occur
Qualifying exception severity based
upon temperature does not consider the potential impact
of an unplanned failure
At present, there is no scientific
method for accurately predicting time to failure based
upon operating temperatures of electrical or mechanical
components. In order to reduce the likelihood of an unplanned
failure, every exception detected should be investigated
for cause and properly repaired as soon as possible.
March
29, 2004
Sponsored
by:
Preventing a
Transformer Fireworks Display
Infrared inspections of oil filled transformers
can help to increase reliability and extend transformer life.
Detecting hotspots on the bushings of these transformers
may also help to prevent a catastrophic explosion.
Hot spots on transformer bushings are usually
due to a loose or deteriorated electrical connection. Frequently,
the source of a hot bushing connection is external to the
transformer and can be corrected by repairing the defective
connection. However, loose connections which originate within
the transformer case can represent an extremely dangerous
condition.
Loose electrical connections within an oil-filled
transformer can lead to a condition known as arcing. When
arcing occurs in oil, the molecular structure of the transformer
oil breaks down forming several combustible gases. The most
significant gases produced are acetylene, hydrogen, methane,
ethane, and ethylene.
The amount of gas produced will depend upon
the temperature of the arc and length of time; however, even
small amounts of gas can lead to a potentially explosive
condition. In a sealed, oil-filled transformer these gasses
can build to a potentially explosive level within a very
short time. In short, combustible gases combined with an
arcing condition within a transformer are a recipe for potential
disaster.
When inspecting oil filled transformers,
any inexplicable temperature rise on bushings should be
investigated and corrected immediately. Performing a dissolved
gas analysis of the transformer oil is recommended if the
cause of the problem is suspected to originate within the
transformer.
April
5, 2004
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by:
How Delta T's
Understate Priorities
For years, thermographers have traditionally
reported apparent Delta T measurements when documenting their
findings. Using a default emittance value between .8 and
1.0, apparent temperature measurements are recorded regardless
of actual target emittance. While this methodology is fast
and easy, it can lead to significantly understated Delta
T repair priorities.
The temperature displayed by a radiometer
is largely dependent upon the emittance and reflected temperature
values entered into the radiometers computer. Typically,
errors in either of these settings will cause temperature
measurement errors that are exponential in nature and can
cause large errors in reporting Delta T’s.
Example: Using an emittance value of 1.0
a thermographer measures the apparent Delta T between two,
uninsulated electrical bus bars to be 44ºC. How much
can observed temperature vary due to emittance values?
Emittance
1.0
.90
.80
.50
.20
Comp 1
86
94
102
143
265
Comp 2
42
46
51
73
124
Delta
T
44
48
51
70
141
From the above, the following observations
can be made:
Emittance can have a significant impact
on Delta T measurements
The greater the variation between an
object’s true emittance and radiometer settings,
the more understated the Delta T
Repair priorities may be significantly
understated if accurate emittance values are not utilized
As there is no way to correct for
errors introduced by apparent Delta T measurements, thermographers
should utilize correct emittance values whenever possible. As
always, all thermal anomalies detected during an infrared
inspection should be investigated and proper corrective
measures undertaken as soon as possible.
April
12 2004
Sponsored
by:
Imager Settings
for MCC Inspections
Infrared inspections of electrical distribution
systems frequently include motor controllers. Proper imager
settings and inspection technique are imperative In order
to accurately inspect these critical electrical devices.
Industrial motors of all sizes are frequently
controlled by remote devices known as motor controllers.
Motor controllers are small to large metal-clad devices containing
one or more large solenoids that control starting/stopping,
motor speed, and rotation direction.
Motor controllers often contain a number
of electrical devices operating at widely differing temperatures.
These devices include control circuits, transformers, fuses,
circuit breakers, contactors, thermal overloads, and circuit
conductors. The temperature of these devices can range over
hundreds of degrees.
When performing an infrared inspection,
setting a thermal imager’s controls to encompass the
whole motor control in a single view is not recommended as
significant problems can be overlooked. For best results,
we recommend the following:
Ensure that subject motor controller
is under load
Image from a distance that permits viewing
only of the subject controller components.
Perform inspection in direction of line
to load side of motor control circuit
View subject components individually
Adjust level/gain settings to optimize
image for each component inspected
Compare features of similar components
to each other, noting inexplicable differences
For controllers with multiple contactors,
it will be necessary to inspect each contactor individually
while under load. Be sure to allow sufficient time for
subject contactor to achieve running temperature.
April
19, 2004
Sponsored
by:
Inductive Heating
Hot Spots
Loose connections, overloading and imbalanced
loads cause overheating of components within an electrical
system. Depending upon construction and operation of the
electrical system, a perplexing and possibly serious condition
called inductive heating can cause non-current carrying components
to overheat.
As current flows through an electrical circuit,
a magnetic field forms around the conductor. When current
flow is high, a strong magnetic field can develop and extend
for several inches around the subject conductor(s). If ferrous
materials such as steel are positioned within this magnetic
field, they can heat up even though they are not part of
the circuit.
Inductive heating can occur on bus supports,
cable tray fasteners, bushing skirts and switchgear enclosures.
Affected components can become hot enough to cause significant
heat damage or even skin burns. The temperature of the affected
component will depend upon the strength of the magnetic field,
and the composition and location of the affected component.
Because inductive heating can cause
components to reach temperatures of over 200ºF, thermographers
should pay particular attention whenever combustible materials
or dielectric insulation are located near, or in contact
with, an inductively heated item.
April
26, 2004
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by:
How FPA Imagers
Differ
Most modern thermal imagers utilize a Focal
Plane Array (FPA) detector. Although the term FPA is widely
used, it is frequently misunderstood. Since detector type
can affect imager performance it is imperative to understand
the differences among FPA detectors.
The term Focal Plane Array is a non-standard
industry term which applies to modern thermal imagers that
utilize a detector chip with multiple picture elements configured
in a flat, single-plane array. Each pixel of an FPA is an
independent sensor capable of detecting infrared energy.
When arranged in an integrated array, these pixels form a
sensor capable of producing relatively high resolution images
compared to older, single or multi-element scanned detectors.
At present, there are two distinct types
of FPA detectors:
Cooled FPA
Microbolometers (Uncooled FPA)
Cooled FPA imagers are short wave only,
contain a Stirling cycle cooler and require approximately
5-7 minutes of cool-down time after initially turning on
the unit. Cooled FPAs were initially imtroduced in the mid
1990’s and revolutionized thermography with their small
size and high resolution imagery. They have been largely
replaced by market demand for uncooled microbolometer imagers.
Uncooled FPA imagers or microbolometers
are long wave only, do not contain a cryogenic cooling
system and typically require less than one minute to produce
an image after initially turning on the unit. Uncooled
FPAs were first introduced in the late 1990’s and
have seen many improvements over time. Nearly every thermal
imager currently being offered for PPM and PdM applications
utilizes a microbolometer detector.
May
3, 2004
Sponsored
by:
Frequency of
IR Roof Inspections
The benefits of thermography for condition
assessment of insulated roofs are well documented. Performed
on a regular basis, infrared thermography can help to extend
the overall life of a roofing system when utilized as part
of a preventive maintenance program.
As a building component, roofing systems
tend to be out-of-sight and out-of-mind. Despite the critical
role they play in keeping a facility dry, many roofs garner
little attention until they begin to leak. In order to minimize
damage, it is imperative that roof leaks be detected and
repaired at an early stage.
Many roofs can gain significant quantities
of moisture in a very short period of time. In the case of
retrofitted roof systems, whole roof sections can become
saturated in a matter of weeks while leaking little or no
water into the occupied spaces. By the time a roof leak is
noticed within the building, replacement may be the only
option available.
For best results, insulated roofs should
be thermographically inspected at least twice per year (e.g.
Spring and Autumn) in accordance with published standards
and guidelines. Semi-annual infrared inspections can help
to identify new areas of moisture damage and help to ensure
that recent repairs are performing in a watertight manner.
Infrared findings should be correlated with a thorough visual
inspection and other pertinent data to formulate an effective
roof maintenance strategy.
For information on infrared training
or certification or to obtain a copy of the Guideline
for Performing Infrared Inspections of Building Envelopes
and Insulated Roofs, contact Infraspection Institute
at 609-239-4788.
May
10, 2004
Sponsored
by:
Infrared Windows for Electrical Switchgear
Traditionally, proper conduct of an infrared
inspection of energized electrical switchgear has required
that panel covers be opened or removed prior to the infrared
inspection. IR transmissive windows and viewports offer an
alternative to this practice; however, several important
issues must be considered prior to installing windows or
viewports.
For many years, safety standards and laws
have required that only qualified persons work on or near
exposed energized electrical components. As safety standards
have evolved, many facilities have sought ways to eliminate
exposure of personnel during an IR inspection and the potentially
lethal injuries associated with an arc flash.
Currently, a wide variety of commercially
available inspection ports and IR transmissive windows are
being offered as an alternative to removing panel covers
for an infrared inspection. Prior to installing such devices
one should bear the following in mind.
Ascertain spectral response of chosen
window to ensure that it is appropriate for use with your
imager
Determine field-of-view for the subject
window
Identify number of windows and positioning
to ensure adequate coverage
Evaluate whether installed viewports
will compromise safety by allowing easier access to energized
components
Consult with switchgear manufacturer
to ensure that window installation will not void warranty
or ratings of switchgear enclosure
Because much of the marketing information
for windows is misleading, caution is recommended when
considering the installation of windows in switchgear enclosures.
This Tip of the Week was
submitted by Vance Cowper, Infraspection
Institute Certified Infrared Thermographer #6370.
Vance is employed by MCI.
May
17, 2004
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by:
Selecting an IR Training Firm
As thermography has gained in popularity,
the demand for training services has also increased. Since
operator training can have a profound effect on the success
of an infrared program, obtaining quality training is of
paramount importance.
At present, there are several firms that
offer infrared training and certification. While nearly all
infrared training firms refer to their training courses by
level (1, 2, or 3), there are no standards which dictate
the content of any offered course. As a result, training
courses can vary widely between firms.
When choosing an infrared training firm,
be certain to:
Examine course curriculum to ensure
that it meets one’s needs
Ensure that course will be germane to
all infrared imagers, regardless of age
Ascertain if Certification is included
with course, its expiration date, and renewal fees
Determine number of years training firm
has been in business - not the
cumulative total of staff years
Insist that instructors be practicing
thermographers with documentable field experience in their
area of instruction
Lastly, beware of claims that training is “vendor
neutral”. It is impossible for training firms to sell
infrared equipment or train for equipment manufacturers without
being biased. Firms who train for manufacturers work for
manufacturers and cannot provide the unbiased information
students deserve. Simply put, no man can serve two masters.
Infraspection Institute
has been providing infrared training and certification
for infrared thermographers since 1980. Our Level I, II,
and III Certified Infrared Thermographer™ training
courses meet the training requirements for NDT personnel
in accordance with the ASNT document, SNT-TC-1A. All courses
are taught by practicing, expert Level III thermographers
whose field experience is unsurpassed anywhere in the world.
We teach effective, real-world solutions using the latest
standards, software and technology. For more information
call 609-239-4788 or visit us online at www.infraspection.com.
May
24, 2004
Sponsored
by:
Ways to Prevent Spam
Spam is that unwanted email that shows up
in our email Inboxes on a regular basis. If you are not careful,
you may find yourself receiving hundreds of unwanted emails
each day. There are a number of actions you can take to limit
the amount of unwanted email and preserve valuable time.
Spammers acquire email addresses in various
ways. The most insidious is tricking you into confirming
your email address. Frequently, the spammer accomplishes
this by sending you spam with a message in the text that
says something like: “Click here to be removed from
our list.”
Of course, the instant you reply, the spammer
knows that they have reached a valid email address - yours!
You have also just confirmed that you read and respond to
email. Ignore the “remove me” choice and just
delete the unwanted email
If you use the Out of Office reply feature
of your email program, spammers will automatically receive
confirmation of your email address when your program responds
to their spam by advising them of your absence. If you wish
senders to receive a response during your absence, have incoming
email routed to a person in your office who can send out
a message for you when necessary.
In short, there is no way to prevent
spam. However, you can minimize the amount you receive
by not confirming your email address to spammers when they
send you unwanted solicitations.
Windows are semi-transparent materials placed
between an object and an infrared instrument to separate
conditioned from unconditioned spaces. When measuring temperatures
through a window, it is imperative to know and enter the
Transmittance value of the window into your radiometer’s
computer to help ensure temperature measurement accuracy.
Because no object is 100% transmissive,
infrared windows will always have Transmittance values of
less than 1.0. Following the procedure listed below, it is
possible to calculate the T value of any window.
Equipment Required:
Calibrated imaging radiometer with a
computer that allows user to input Reflected Temperature
and Emittance values .
Blackbody simulator with E > 0.95
heated close to temperature of target to be measured.
Window that is semitransparent in the
waveband of the imaging radiometer.
Method
Place imaging radiometer at desired
distance from blackbody simulator.
Aim and focus imager on blackbody simulator.
Place crosshair on
center of blackbody simulator.
Set imager’s E control to 1.0
Measure and compensate for Reflected
Temperature.
Measure and note apparent temperature
of blackbody simulator.
Place window directly in front of imaging
radiometer’s lens.
Without moving imager, adjust E control
until observed temperature matches value obtained in Step
5 above. The displayed E value is the Transmittance percentage
for this window with the subject imaging radiometer. For
greater accuracy, repeat above a minimum of three times
and average results.
The above procedure is described in
detail in the Guideline for Measuring and Compensating
for Reflected Temperature, Emittance, & Transmittance
available from Infraspection Institute. For more information
or to place an order, call 609-239-4788 or visit us online
at www.infraspection.com.
June
7, 2004
Sponsored
by:
NFPA 70E & Energized Electrical Work Permits
On February 11, 2004, the sixth edition
of NFPA 70E Standard for Electrical Safety in the Workplace
became available superceding all previous editions. In addition
to a new look, layout, and title, the latest edition of NFPA
70E contains several important changes including the requirement
for an energized electrical work permit.
The 2004 edition of NFPA 70E requires an
Energized Electrical Work Permit if live parts are not placed
in an electrically safe work condition. NFPA 70E requires
that the permit shall include, but not be limited to, the
following items:
Description of the circuit and equipment
to be worked on and their location
Justification for why the work must
be performed in an energized condition
Description of the safe work practices
to be employed
Results of the shock hazard analysis
Determination of shock protection boundaries
The Flash Protection Boundary
Necessary Personal Protective Equipment
to safely perform the assigned task
Means employed to restrict the access
of unqualified persons from the work area
Evidence of completion of a job briefing,
including a discussion of any job-specific hazards
Signature(s) of authorized personnel
who are approving energized work
Work performed on or near live parts by
qualified persons related to tasks such as testing, troubleshooting,
voltage measuring, etc., shall be permitted to be performed
without an energized electrical work permit, provided appropriate
safe work practices and personal protective equipment are
used.
Copies of NFPA 70E can be purchased
by calling the National Fire Protection Association at
1-800-344-3555 or online at: www.nfpa.org.
June
14, 2004
Sponsored
by:
NFPA 70E & Arc-Rated Face Shields
Personal Protective Equipment, including
fire resistant clothing, has long been specified by NFPA
70E. The 2004 edition contains several important changes
including a new requirement that workers wear an arc-rated
face shield.
The 2004 edition of NFPA 70E requires workers
to wear an arc-rated face shield if live parts are not placed
in an electrically safe work condition and work is to be
performed within the Arc Flash Boundary. This new requirement
applies to work having a Hazard/Risk Category 2. Face shields
must have a minimum arc rating of 8, with wrap –around
guarding to protect not only the face, but also the forehead,
ears, and neck. A flash suit hood may be used in place of
an arc-rated face shield.
For electrical systems that are rated at
600 volts or less, NFPA 70E defines the Arc Flash Boundary
as a minimum of 4.0 feet for systems having an available
bolted fault current of 50kA. This Arc Flash Boundary distance
increases as available fault current and/or clearing times
increase and may be calculated using the formulae found in
Article 130.3 (A).
Copies of NFPA 70E can be purchased
by calling the National Fire Protection Association at
1-800-344-3555 or online at: www.nfpa.org.
June
21, 2004
Sponsored
by:
The Importance of Follow-up Inspections
Many companies that contract thermographic
inspections are usually provided with a technical report
clearly identifying areas and conditions that need attention.
From the information contained in the report, maintenance
personnel investigate suspect areas and make appropriate
repairs.
Once corrective actions have been completed,
it is extremely important to have the thermographer return
to reinspect suspect areas to ensure that the original discrepancies
have been properly repaired. One professional infrared testing
company reported as many as 80% of exceptions were still
present after repairs had reportedly been made. In this case,
the follow-up inspection was actually more important than
the original inspection.
The follow up inspection is also a good
time to have the thermographer inspect equipment that may
have been off line or not under load at the time of the initial
infrared inspection.
Infrared thermography has the highest
return on investment for all of the PPM technologies. It
has been calculated at about ten dollars saved for every
dollar invested. So, it is important to reinspect after
repairs. A follow up infrared inspection can make a fair
PPM program into an exceptional PPM program.
This Tip of the Week was submitted
by Erich Black, of
Black & Associates, 15210 Priceville Road, Sparks,
MD 21152. Erich may be contacted at 410.472.2416
or via e-mail.Visit
their web
site.
June
28, 2004
Sponsored
by:
Preparing for
IR Inspections of Electrical Systems
Perhaps the most common application for
infrared thermography is PdM inspections of electrical distribution
systems. However, in focusing on the inspection, many overlook
the critical step of properly preparing for the inspection.
Proper planning prevents poor performance.
For IR inspections of electrical distribution systems, this
planning should begin well in advance of the inspection.
The following are some of the not-so-obvious considerations
that should be part of every inspection.
Performance standard(s) or Guidelines
to be followed
Safety standards and rules applicable
to the work areas
Thermographer and qualified assistant(s)
should be trained as qualified persons as defined by NFPA
and OSHA standards
Necessary Personal Protective Equipment
including fire resistant clothing
Provisions for First Aid and CPR
Pre-job safety briefing prior to the
commencement of the inspection
Lastly, infrared inspections should only
be performed by experienced, certified infrared thermographers
who thoroughly understand the theory and operation of electrical
distribution systems. Properly planning for your next infrared
inspection can provide for a safer and more efficient inspection.
For more information on thermographer
training and certification, or to order a copy of the Guidelines
for Infrared Inspections of Electrical and Mechanical Equipment,
call us at 609-239-4788 or visit us online at: www.infraspection.com
July
6, 2004
Sponsored
by:
IR is for Integrity & Responsibility
During the past twenty years, professionalism
has been a concern frequently discussed among practicing
thermographers. Few realize that true professionalism begins
with the individual and is the responsibility of every member
of the infrared community.
Frequently it seems that thermography has
matured more rapidly than some of its participants. The infrared
industry has more than a few who seem to go out of their
way to accentuate the negative either by word or by deed,
often in a sensational fashion. Unfortunately, this behavior
reflects on the thermographic community as a whole.
Because professionalism is determined by
those who practice thermography, it is incumbent upon every
infrared professional to define our technology on a daily
basis through their actions. If you are a practicing thermographer
the following are some ways you can help to enhance the image
of our profession.
Always promote thermography in an honest
and positive manner
Do not offer derogatory or negative
comments about a competitor
Always use equipment appropriate for
the subject inspection
Make sure that your formal training
is current and the highest level you can achieve
Always work within the limits of your
training and experience
Whenever possible, adhere to published
Standards or Guidelines
Lastly, when promoting your services
or products, do so only in an honest and forthright manner.
We invite infrared professionals to act responsibly and
with integrity by adhering to the simple concepts outlined
herein. Doing so will maintain and enhance the professional
image of our technology.
July
12, 2004
Sponsored
by:
Training & Equipment:
Which First?
We’ve all heard the phrase, “Put
the horse before the cart.” When it comes to thermography,
many people put the cart in front of the proverbial horse
by buying infrared equipment before obtaining proper training.
Purchasing the correct imager is a challenge
for many reasons: initial purchase price can be costly, no
imager is capable of performing all applications, imager
performance varies widely, and available specifications are
frequently exaggerated.
Further compounding this challenge is that
many manufacturers offer “free training courses” as
sales incentives to purchasers of new equipment. Frequently
these free courses are taught by inexperienced/unqualified
instructors, are introductory in nature, and are designed
as operator courses for the subject equipment omitting important
theory or applications. Because these courses are taught
after equipment is delivered, inexperienced purchasers lack
the knowledge required to make an informed decision when
selecting new equipment.
In order to properly select and
specify infrared equipment, buyers should put the horse
before the cart by receiving quality certification training
from an independent institute prior to equipment purchase.
For new users, training should include infrared theory
and heat transfer concepts, equipment selection and operation,
image capture and analysis, standards compliance, applications-specific
inspection techniques, documentation of findings, and temperature
measurement techniques.
Infraspection Institute offers Level
I, II, and III training and certification for thermographers
worldwide. Our cutting-edge infrared training courses are
taught by highly-experienced thermographers in a friendly,
relaxed atmosphere without marketing hype. For more information
call 609-239-4788 or visit us at www.infraspection.com.
July
19, 2004
Sponsored
by:
Wind as an Error
Source
As individuals, most of us can appreciate
the cooling effects of a breeze on a hot summer day. As thermographers,
wind represents a greater technical challenge in the form
of a potential error source when measuring temperatures radiometrically.
As wind moves across the surface of an object,
convective heat transfer occurs. In general, wind will either
cool a warm target or warm a cool target. The rate of convective
heat transfer will primarily depend upon: velocity of the
wind, temperature differential between object and wind, and
surface film coefficient of the object.
Wind can significantly alter the temperature
of an object while the windy condition is present. Frequently,
the effects of wind may remain for a significant period of
time after the wind has stopped and the object has returned
to its normal temperature.
Because radiometric equipment cannot compensate
for the effects of wind on an object, it is best to avoid
wind when measuring object temperatures. To eliminate wind
as an error source:
Wait until wind stops
Temporarily shield target from wind
Measure downwind side of target provided
that object is sufficiently large
Always allow sufficient time for target
to return to normal temperature once wind has been eliminated.
If it is not possible to avoid wind, one should report wind
velocity and direction when recording image data.
Lastly, thermographers should resist
any temptation to apply ‘Wind Chill Charts’ to
correcting for the effects of wind. Wind Chill charts have
been designed to estimate the net effect of wind and ambient
temperature on exposed human flesh and are not applicable
to inanimate or industrial objects.
July
26, 2004
Sponsored
by:
Role
of IR Inspections for
Electrical Distribution Systems
Infrared inspections
can be a valuable tool for detecting problems within electrical
distribution systems. Understanding when and where to utilize
thermography is key to obtaining optimum benefit.
Infrared inspections can detect and document
evidence of loose/deteriorated connections, overloaded circuits,
imbalanced loads, harmonics, and defective equipment. In some
cases, infrared inspections can detect evidence of problems
that may be overlooked by traditional electrical testing.
Infrared inspections should be used to supplement, but not
replace, regular preventive maintenance.
When setting up an IR inspection program
for an electrical distribution system, keep the following
in mind:
Inspections should be performed at least
annually
Inspections should be conducted with
the electrical system under normal load
Inspections require clear line-of-sight
to inspected components
When possible, IR inspections should
be performed 4 to 6 weeks in advance of PM shutdown to allow
time to order necessary parts
Exceptions should be reinspected after
repair to ensure that repairs were effective
All new/retrofitted equipment should
be inspected within 24 hours of installation
All findings should be documented in
writing in accordance with the Guideline for Infrared Inspection
of Electrical and Mechanical Systems
Lastly, infrared inspections should only
be performed by certified infrared thermographers who are
thoroughly familiar with the system(s) being inspected.
For more information on thermographer
training and certification or to obtain a copy of the Guideline
for Infrared Inspection of Electrical and Mechanical Systems,
contact Infraspection Institute at 609-239-4788 or visit us
online at www.infraspection.com.
August
2 , 2004
Sponsored
by:
Improving
Accuracy of IR Temperature Measurements
As infrared technology
has advanced, radiometers have become a common tool for many
maintenance technicians and mechanics. Although radiometers
are relatively easy to use, there are several important factors
that influence the accuracy of a radiometer’s readings.
Infrared radiometers offer several advantages when it comes
to temperature measurements.
Measurements are non-contact, non-destructive
and can be obtained quickly. Unfortunately, radiometers are
not self-diagnostic and cannot warn the operator of erroneous
readings. The following are some simple tips that can help
to ensure accurate infrared temperature measurements.
Target should be stationary and at a
stable temperature with a dry surface
Radiometer lens should be clean and free
from obstructions
Radiometer batteries should be fully
charged
IR temperature measurements should be
made perpendicular to target
IR radiometer should be operated at a
distance to ensure that spot measurement size is smaller
than the target
Accurate emissivity and reflected
temperature values should be input into the radiometer’s
computer.
Whenever possible, infrared readings should
be correlated with known temperature values. If a discrepancy
is observed, it could be due to a procedural error in measurement
or the radiometer may require calibration.
For more information on infrared temperature
measurement, or to obtain information on thermographer training
and certification, contact Infraspection Institute at 609-239-4788
or visit us online at www.infraspection.com.
August
10, 2004
Sponsored
by:
IR
Inspections of Electric Motors
Despite the
important role they play in a commercial facility, electric
motors tend to be both out-of-sight and out-of-mind until
they fail. Infrared thermography can be used as a cost-effective
diagnostic tool for detecting problems within electric motor
systems.
Many infrared inspection programs include
motor control circuits but overlook the motor itself. Evidence
of several conditions which can lead to premature motor
failure can be detected with a thermal imager. The following
are suggestions for thermographically inspecting motors.
With cover removed, inspect electrical
connections at the motor junction box. This should be
done in conjunction with the regularly scheduled inspection
of the facility’s electrical system.
Inspect motor casing for localized
hotspots which may be indicative of short circuits within
motor windings
Qualitatively compare individual motors
to similar motors under similar load
When possible, qualitatively compare
inboard and outboard bearings for each motor. If a large
Delta T is present, it may be indicative of misalignment
or a rotor balance problem. If both bearings are hot,
the bearings may be worn or improperly lubricated.
Because no complicated analysis is required,
infrared inspections typically can be performed rapidly
and at a fraction of the cost of other types of motor testing.
Additionally, infrared can detect evidence of misalignment
at lower thresholds than those detectable by vibration
analysis and motor current signature analysis.
Lastly, infrared inspections of motor
bearings and stator should be performed monthly by experienced,
certified infrared thermographers who thoroughly understand
the theory and operation of electric motors.
August
16, 2004
Sponsored
by:
IR Inspections
for Sewer Systems
In regions with
older infrastructure, sewer system integrity is often a primary
concern. Under the right conditions, thermography can often
detect sewer leaks or voids surrounding the system that can
lead to sinkholes.
In the case of sewer systems, thermal
imaging is usually employed during evening hours after
a sunny day. During the inspection, the thermal imager
is maneuvered over the pathway of the subject sewer system
looking for unusual thermal patterns. The imager may be
operated on foot, from a motor vehicle or an aircraft.
Sewer system defects which may be detectable
include leaks to surrounding soil and voids around sewer
piping. The detectability of these defects will be largely
dependent upon:
Depth of sewer system
Amount of loss
Pipe construction
Soil type and ground cover
One should be aware that a negative finding
does not necessarily mean defects are not present; they
simply may not be detectable by thermal imaging. Conversely,
positive findings can be caused by conditions other than
leaks. Therefore, it will be necessary to verify all thermal
data by visual inspection.
The topic of infrared inspections
of buried piping systems is covered in depth in our Level
I Certified Infrared Thermographer™ classes. For
more info on training and class dates, please call or
visit us online at: www.infraspection.com.
August
23, 2004
Sponsored
by:
Gauging Solar Loading
Did you know
that an automobile can be used to gauge solar loading? Under
the correct conditions, a parked car can serve as a cheap,
but effective, pyranometer.
Many types of infrared inspections rely
on solar loading to heat the target so that infrared imaging
may be performed successfully. Applications include, but
are not limited to, low slope roof inspections, concrete
bridge decks, storage vessel levels and latent moisture
within building sidewalls. Ensuring that enough solar loading
has occurred is imperative to collecting good data.
Good solar loading conditions are easy
to recognize – long days with bright sunny skies,
low humidity and no wind. More tricky is being able to
determine if less than optimal conditions are allowing
for appreciable solar gain.
A time tested method for gauging
solar loading is to check the interior of a parked automobile.
With the engine stopped and the windows and doors closed,
allow the vehicle to sit in the sun for up to an hour.
Immediately upon opening the door, check to see if the
vehicle interior has exceeded outdoor ambient temperature.
If a noticeable difference is not detected, feel the
dashboard to see if it has warmed. If not, it is likely
that appreciable solar loading has not occurred and it
may be best to reschedule your solar driven inspection
for another day.
Most problems
on electrical systems are preceded by a change in its thermal
characteristics and temperature, whether hotter or cooler.
A trained
and experienced thermographer is able to identify and analyze
those anomalies prior to costly failures occurring.
Thermography is one of the tools used
by the Bruce Power Predictive Maintenance group which was
created last year. Four thermographers at Bruce B and two
at Bruce A started to perform thermography inspections
of electrical equipment. Baseline inspections have been completed
to this point on the most critical equipment. An example
of a recent successful deployment of thermography is detailed
here.
At Bruce A, Len Bridge and Bob Forrest
performed a thermography inspection of the Unit 4 main
output transformer. Elevated bushing temperatures revealed
an imminent problem. Inspection results successfully confirmed
that the cooler was plugged due to rust buildup. The pictures
describe the story.
Photos by Len Bridge
and Bob Forrest
In the infrared photograph shown
at left, red phase and blue phase high voltage bushings
are operating at higher temperatures than the white
phase bushing. The thermography image led to the
discovery
of a rusty buildup (shown above) that was beginning to plug the
coolers.
September
6, 2004
Sponsored
by:
Transmissivity of Switchgear Windows
As the popularity
of infrared transmissive switchgear windows increases, many
have begun to question how much windows attenuate the observed
infrared data. With no standards governing the manufacture
of switchgear windows, the answer can vary depending upon
the make and model of the window and the selected infrared
equipment.
Infrared transmissive windows have seen
increasing popularity as an alternative to opening electrical
cabinets for infrared inspections. These windows typically
contain an IR transmissive material supported in a metal
frame and are permanently installed at strategic locations
in the switchgear enclosure. During the infrared inspection
the camera lens is placed against the window to inspect
electrical components without having to open the subject
enclosure.
As no material on earth is 100% transmissive
to infrared energy, all infrared windows will qualitatively
and quantitatively attenuate the infrared energy passing
through the window. While it is useful to know the transmittance
of the window’s optical material, there are other
important factors to be considered. It should be noted
that there is no way to compensate for any of the common
error sources listed below.
Many IR windows have optics far smaller
than IR imager lenses vastly reducing the infrared energy
reaching the detector
Switchgear windows that become dirty
over time attenuate IR energy
Some switchgear windows are wavelength
specific and will react differently according to imager
selected
Depending upon cabinet depth, it may
not be possible to obtain clear focus for the subject
components
Prior to installing switchgear windows,
it is imperative to understand their applications and
limitations. For more information on calculating the
transmissivity of switchgear windows, consult the Guideline
for Measuring and Compensating for Reflected Temperature,
Emittance & Transmittance available from Infraspection
Institute.
September
13, 2004
Sponsored
by:
Asphalt or Coal Tar – How
to Tell the Difference
When performing
an infrared inspection of low slope roofing systems, invasive
testing is necessary to confirm the composition and condition
of roofing system components. As asphalt and coal tar are
incompatible materials, it is imperative to use the correct
bitumen to ensure the long term integrity of repaired test
sites.
Asphalt and coal tar are hydrocarbon materials
commonly used for built-up roofing. While both share a
common use in roofing, they are very different in their
chemical composition. Asphalt is a petroleum distillate
and a byproduct of crude oil refining. Coal tar is a bituminous
product that is largely insoluble in petroleum distillates.
Odor is one way to differentiate between
asphalt and coal tar – tar has a distinctive creosote
smell. A more reliable method is to test bitumen solubility
in mineral spirits. This simple test can be performed as
follows:
Obtain a small sample (pea size nugget)
from the subject roof
Soak sample in a small amount of mineral
spirits in an empty glass container such as a baby food
jar
Stir sample gently for about one minute
and note results
If sample dissolves to black liquid – sample
is asphalt; if sample remains intact and/or colors mineral
spirits to a yellow/green color, sample is coal tar.
Once bitumen type has been determined,
one should use appropriate repair materials along with
the same bitumen as indicated by the above test. Doing
so will help to ensure the long term integrity of repaired
test sites.
September
20, 2004
Sponsored
by:
Arc Flash Protection – How
Much Do You Need?
For those who
work near exposed, energized electrical equipment, a popular
question is, “How much arc flash protection do I need?” This
week’s Tip focuses on two ways to answer this question.
NFPA 70E mandates that Fire Resistant
Clothing be worn whenever an employee is working within
the Arc Flash Boundary. For equipment rated at 600 volts
or less, the Flash Protection Boundary is 4.0 feet; this
distance increases proportionally with available energy
levels. The selected flash protection must provide thermal
protection against the potential heat generated should
an arc flash occur.
The amount of heat associated with an
arc flash is dependent upon the amount of energy available
and the distance from the fault. The amount of energy available
is dependent upon available fault current and clearing
time for the fault. NFPA 70E provides two methods for determining
how much FRC is needed.
The first method involves utilizing an
engineering calculation to determine the amount of energy
available for subject components. Employing this formula
usually requires the skills of an electrical engineer and
specific information about the subject equipment including
voltage, amperage and overcurrent protection. Protective
clothing is selected based upon the amount of potential
heat energy determined from the calculation.
The second method utilizes a table
listing electrical equipment and common work tasks. By
identifying the work task and the category of subject
electrical equipment, one may determine the Hazard/Risk
Category associated with a specific task. Once the Hazard/Risk
Category has been determined, a second table is utilized
to determine the required PPE for the particular Hazard/Risk
Category.
September
27, 2004
Sponsored
by:
Storing & Transporting Your
IR Equipment
Among thermographers,
few things can cause an acute stomach ache like damaged equipment.
Damaged equipment is not only costly to repair, but may also
interrupt an inspection program while the equipment is being
repaired.
With infrared equipment, an ounce of prevention
is worth several pounds of cure. Fortunately, preventing
equipment damage is easy and inexpensive. Some of the best
ways to prevent damage are as follows:
Store IR equipment in hard sided shipping
cases that have die cut foam to fit the subject equipment
and its accessories
Keep lens caps on camera and extra
lenses while in the storage case
When not in use, store IR equipment
and accessories in a cool, dry place
When transporting or shipping equipment,
utilize extra padding to prevent components from shifting
in the carrying case
When traveling on an aircraft, hand-carry
your imager. Be sure to allow extra time when going through
airport security and encourage inspectors to be extra
careful with your equipment
Lastly, maintain your equipment
carrying cases in good working order. Repair or replace
defective or worn hardware. If your case should become
worn, replace it with a new original or an after-market
case suitable to the task. Some shipping cases are guaranteed
for life and replacement parts may be available at no
charge.
October
4, 2004
Sponsored
by:
Intrinsically Safe Equipment
Intrinsically
safe test equipment is a requirement for workplaces where
combustible gasses may be present. Prior to performing an
infrared inspection in such areas, it is important to understand
the meaning and importance of this requirement.
Intrinsically safe is a term that applies
to test instruments that will not produce sparks or thermal
effects capable of igniting a flammable vapor. Intrinsically
safe equipment is frequently required in mines, chemical
refineries, and in areas where combustible gasses, vapors,
or dust may collect. Using instrumentation other than intrinsically
safe in these areas could cause a potentially lethal fire
or explosion.
Presently, most infrared inspection equipment
is not rated as intrinsically safe. Because of this, infrared
equipment not rated as intrinsically safe should never
be operated in an area where combustible gasses or vapors
are present.
In areas where there is a potential
of combustible gas accumulation, the area should be sampled
for combustible gasses and oxygen content prior to the
infrared inspection to ensure that the area is safe to
enter. Once area has been deemed safe, the area should
be continuously supplied with fresh air and monitored
regularly during the inspection.
October
11, 2004
Sponsored
by:
How to Core Sample a Roof
Currently published
industry standards require that core samples be obtained
when performing infrared roof moisture surveys. Properly
procuring and patching core sample sites can help to maintain
watertight integrity of sample sites.
Core sampling a roof involves physically
removing a portion of the roof membrane and insulation
layers to ascertain the composition and condition of roofing
system components. Core samples may be square or round
and range from a couple of inches in diameter to a several
square feet in size.
The following procedure outlines the steps
in sampling and patching 2” diameter core samples
on gravel-surfaced, built-up roofing systems.
Locate sample site on flat portion
of roof not subject to ponding
Spud gravel off membrane for 12” diameter
area. Use wire brush to remove dust
Use core cutter to sample through
membrane down to deck. Do not cut through roof deck
Fill sample hole approximately ¾ full
with cold roof mastic compatible with existing roof bitumen
Install plug made from perlite insulation.
Cold mastic should flow up and around plug once it has
been seated firmly on roof deck at bottom of hole. Top
of plug should be within 1/8” of top of sample
hole when plug has been pushed to bottom
Coat cleared area with roof mastic
Center 6” diameter disk of 15
lb roofing felt over plug. Firmly press felt down to
remove air pockets and fish mouths.
Apply thin layer of roof mastic over
6” felt
Center 12” diameter disk of
15 lb roofing felt over plug. Firmly press felt down
to remove air pockets and fish mouths
Apply generous layer of roof mastic
over 12” felt. Replace gravel and outline area
with spray paint
Prior to sampling, determine if
roof is under any warranty that could be voided by sampling.
Always obtain permission to perform any invasive testing
before you begin.
October
18, 2004
Sponsored
by:
IR for Refractory Inspections
Infrared thermography
is frequently used for condition monitoring of refractory-lined
vessels such as boilers, furnaces, reformers, and cat crackers.
By inspecting these same vessels during different stages
of start-up, one can find problems that may not be detected
when the subject vessel is operating at full rates and temperature.
Within refractory-lined vessels, refractory
will tend to expand as temperature increases. In a perfect
world, there should be no detectable thermal anomalies
during low temperature operation but, in fact, you may
be able to readily detect refractory problems while the
unit is operating at below normal temperatures.
During startup, one may notice that some
hot spots will disappear once the vessel has reached normal
operating condition. This is because the refractory has
expanded and sealed off cracks within the interior of the
unit. It is not uncommon to see an exception that has reached
near critical temperature to completely disappear or cool
to an acceptable limit once the vessel has reached full
rates. Hot spots remaining after startup may indicate serious
problems and should be closely monitored.
By identifying exceptions at lower operating
temperatures, one may better predict where a future problem
or failure may occur. For vessels subject to cyclical loading,
these same areas are usually the first to deteriorate due
to an excessive amount of expansion and contraction.
When used as a quality assurance or condition monitoring tool, infrared
thermography can help to avoid unnecessary or unexpected shutdowns
thereby saving a facility valuable production time and money.
This Tip of the Week was submitted
by:
Sonny James
Thermal Diagnostics Limited
15 Robertson Street
Les Efforts East
San Fernando
Trinidad, West Indies
Build it and
they will come. This romantic notion worked for Kevin Costner
in the film, Field of Dreams; however, real life and business
are rarely that simple. Once you have built your infrared
inspection business, there are time-tested ways to help ensure
that customers will come.
Getting prospects to come to your business
involves more than setting up shop and hanging out a shingle.
In order to thrive, you have to let prospects know that
you are open for business and that you are ready to respond
to their needs. The following are some of the most effective
ways to get your message out to potential customers.
Have a professional artist design
a color brochure that fully describes your capabilities
and strengths along with the benefits that customers
can expect from your services.
Engage a website professional to design
a website that mirrors your advertising brochure. Whenever
possible, choose a domain name that is easy to remember
and contains your company name only. Be certain to update
your website periodically.
Network with other professionals that
can bring you work through their business activities.
Architects, engineers, contractors and consultants can
be excellent strategic partners. Once you have established
a relationship, you reap the benefit of their sales efforts
at no cost.
Once you have identified prospects
within your region, hit the bricks and do some old fashioned
selling. In this day of internet selling, email and instant
messaging, putting a human face on your company can be
worth its weight in gold.
Lastly, advertise your company in
an online directory where prospects are likely to visit.
At present, IRINFO.ORG receives 250,000 visitors each
year, many of whom are looking to hire an infrared professional.
Listing your company in our Directory of IR Inspection
Companies can mean the difference between working hard
or hardly working.
November
1, 2004
Sponsored
by:
Maintaining Situational Awareness
Many animals
and even some people are credited with having a sixth sense
for knowing or anticipating events before they happen. The
benefits of this seemingly supernatural power can be enjoyed
by applying a discipline known as situational awareness.
Situational awareness is a technique that
has been practiced by pilots and military personnel for
several years. Situational awareness is a discipline that
requires a person to be constantly aware of his/her surroundings
and to constantly anticipate what might happen next. By
constantly being aware of what might happen one is better
able to plan an appropriate response before an event occurs,
thereby avoiding surprises.
With the hazardous environments in which
thermographers frequently work, practicing situational
awareness make sense. Thermographers can apply the discipline
of situational awareness by observing the following:
Always be aware of your immediate
surroundings and the hazards contained therein
Recognize how the actions of others
might affect your situation
Be aware of weather or environmental
conditions that could present a hazard
Have an emergency response for any
situation that could occur
Know where emergency equipment and
communications devices are located
Identify both primary and secondary
evacuation routes for use in case of an emergency
Practicing situational awareness
means that you plan for what could go wrong instead of
what is likely to go wrong and have preplanned responses
for any eventuality. Taking some time to practice situational
awareness can vastly improve your personal safety by
helping to eliminate surprises and the confusion that
goes along with them.
November
8, 2004
Sponsored
by:
It’s Not That
Easy
Ever wonder why
magicians never reveal their secrets? It's because magic,
like most things, is easy once you know the trick. When describing
thermography in lay terms, it is easy to over emphasize simplicity
and forget the source of the true magic behind thermography – the
thermographer.
An infrared inspection system consists
of infrared imaging equipment, a thermographer, and the
knowledge that he/she possesses. Of these three things,
the greatest limiting factor in an infrared inspection
system is the thermographer.
In order to be an effective a thermographer,
one must be trained in the following:
Theory and construction of the object
or system being inspected
Infrared theory and heat transfer
principles
Use and operation of infrared imaging
equipment
Non-contact temperature measurement
error sources and how to avoid or correct for them
Site-specific safety requirements
and the use of appropriate PPE
In addition to the above, qualified thermographers
must also be experienced with inspecting the subject system.
When all things are considered, effective thermographers
need considerable training and field experience. Making
thermography look simple is a true testament to the skills
of a professional thermographer.
The next time you hear the dismissive
claim that thermography is easy, remember, it is only
easy after someone has invested considerable time and
effort to learn the art and science of the trade. In
a magic show, the magic comes from the magician, not
the wand. In thermography, the magic comes from the thermographer.
November 15, 2004
Sponsored by:
Visual Inspections & Thermography
You’ve probably heard the saying, “You can’t see the forest because of all the trees.” Sometimes thermographers can’t see visible discrepancies for the thermal imagery.
Thermal imaging is a very powerful tool for detecting, displaying and recording thermal patterns across the surface of an object. With the high tech information that thermography provides, it’s often easy to overlook problems that are visually apparent. Taking some time to study your subjects and their surroundings can provide additional information that can aid in your analysis or even discover deficiencies that your thermal imager may not detect.
When performing an infrared inspection, be certain visually inspect targets and their surroundings to:
·Note how nearby hot or cold objects may affect the inspected items
Identify environmental conditions that may adversely affect infrared data
Ascertain how target characteristics such as emittance will impact infrared analysis
Detect signs of previous overheating such as discoloration, oxidation or melting
Correlate visual observations to the displayed thermal image
Lastly, many published standards and specifications require visual inspections be performed simultaneously with thermographic testing. Taking the time to visually inspect your subjects may improve your diagnoses and help to ensure that your inspections are compliant with industry standards.
November 22, 2004
Sponsored by:
Warm Lighting Circuit Breakers
When performing infrared inspections of branch circuit panels, lighting circuits will often appear warmer than adjacent circuits. If adjacent circuits are lightly loaded, the warmer circuits may be indicative of a normal condition or they may represent a more serious condition.
For electrical panels with single-phase branch circuits, is often quite normal for lighting circuit circuits to appear warmer as they frequently have some of the highest loads within the panel. To confirm this, load readings should be obtained with a true RMS ammeter to determine that the subject breakers are operating within specifications. For long term use, it is recommended that circuits operate at less than 80% of their rated capacity.
If lighting circuit breakers are used as switching devices, they must be rated as Switch Duty. Using non-switch-rated breakers can cause excess wear on the breaker contacts. To determine the integrity of breaker contacts, one should remove the breaker from service and perform a contact resistance test through the breaker with the breaker in the closed position. Such testing should be performed with a digital low resistance ohmmeter.
If lighting circuits have fluorescent fixtures or other solid state devices connected to them, the circuits are likely to contain significant harmonic content. To determine if significant harmonics are present, the subject circuit should be tested with a harmonics analyzer.
In lieu of testing a suspect breaker, you may wish to replace it with a new one and re-image the subject circuit to ascertain if the situation has improved.
November 29, 2004
Sponsored by:
Connecting the Dots
One of the most challenging aspects of performing infrared inspections involves directing a qualified assistant in outlining exceptions on the surface of the ground or an insulated roof.
Thermographers who perform infrared inspections of flat roofs or underground piping systems often outline the perimeter of exceptions with spray paint. Directing a qualified assistant to accurately outline exceptions can be both time-consuming and frustrating. The following suggestions can help to speed inspections while preserving coworker relations.
When using spray paint to mark at ground level, use a spray paint and dispenser designed for the task
Make sure surfaces to be marked are clean and dry and will not be damaged by spray paint
Never spray paint where wind may carry paint to unintended surfaces
Be certain of target before marking – make certain shoes/hands are clear
Consult Material Safety Data Sheets before using spray paint for any health and usage precautions
When outlining the perimeter of an exception, use a series of dots to outline the most prominent features of the exception. These dots can then be connected with a solid line once their location is deemed satisfactory. Depending upon weather and target conditions, spray painted lines will often show clearly within the thermal image.
December 6, 2004
Sponsored by:
Change Routes with the Season
To everything there is a season. The same is true for infrared inspection routes within facilities where equipment or systems are operated seasonally.
Traditionally, many facilities perform infrared inspections on an annual basis. While this approach may detect deficiencies within operating systems, systems not under load due to seasonal or operational conditions cannot be effectively inspected.
Examples of seasonally operated equipment include heating/cooling systems, production machinery, and the electrical distribution system. Effective infrared inspections of seasonally operated equipment begin at the planning stages and should include the following:
Develop an inventory list of equipment to be inspected
Group seasonally operated equipment into dedicated routes
Ascertain operating times for subject systems
Schedule infrared inspections for the beginning of operating season
Inspect subject systems while under normal load
Be certain to perform a follow up inspection for all detected exceptions once necessary repairs have been completed. As always, remember to observe all necessary safety precautions before, and during the infrared inspection.
December 13, 2004
Sponsored by:
Alternatives to Thermal Images
Using thermograms to document exceptions is a time-tested common practice in thermography. At times, this practice can be cumbersome and confusing, especially with large structures.
Simply defined, thermograms are two-dimensional hardcopy images that represent the thermal patterns across the surface of an object. For years, thermographers have utilized film or paper to produce records of the imagery provided by their thermal imager. Traditionally, thermograms work well for small objects or for exceptions that are small in size.
Documenting thermal patterns on large structures such as multi-story buildings or flat roofs can prove to be a challenge. This challenge may be further compounded when observed exceptions are large in size. A simple solution to these challenges is to utilize architectural drawings, elevations, or schematics in place of, or in addition to, hardcopy thermograms. When utilizing drawings to document your infrared inspection, keep the following in mind:
Prior to the infrared inspection, obtain drawings with sufficient detail
Verify accuracy of drawings with the subject structure
Be certain to verify site orientation with compass orientation
During the inspection, mark the size and location of exceptions directly on drawings along with thermogram numbers, where appropriate
Whenever possible, obtain extra sets of drawings to be used as file copies or for field use. When utilized properly, drawings can serve as valuable reference tools enabling one to see "the big picture" that is often not possible with several small thermograms alone.
December 20, 2004
Sponsored by:
Our Most Important Tip
With the end of the year upon us, we wish to follow in the grand tradition of saving our best for last. In this Tip of the Week, we address some of the most important issues facing predictive maintenance professionals.
With the holiday season in full swing, we invite PdM technologists and thermographers throughout the world to consider the issues of inventory, reliability and communication and offer our best advice as follows:
Inventory – Take time to reflect on your many blessings such as good health, family and friends.
Reliability – Set time aside to appreciate having friends and relatives in whom you can confide and trust.
Communication – Remember to share your feelings with all of the special people in your life by letting them know what they mean to you.
Spreading cheer and holiday spirit is easy; it begins with each of us as we let others know how we feel about them.
As we enjoy this holiday season, we extend a heartfelt Thank You to all of our readers, friends, and associates throughout the world for everything that you do for us all year long.
May your holidays be filled with peace and joy and your New Year with good health and happiness.
~ Jim & Chris Seffrin
December 27, 2004
Sponsored by:
Using Floor Plans to Identify Locations
In a recent Tip of the Week, we suggested using architectural drawings to supplement, or as a substitute for, thermograms for large structures. Structural blueprints can also be used to reference locations when performing infrared inspections of large physical structures.
Within the blueprint set for any large structure are individual floor plans which usually indicate the location of structural columns. Floor plan drawings are customarily laid out with column rows indicated by letters on one axis and numbers on the other. Using a combination of letters and numbers (A1, B1, etc.) to designate columns enables one to universally reference locations within a structure.
Because columns are permanent, their designations will not change over time and will not be affected by changes in structure usage such as floor layout or office location. When utilizing column line drawings to document your infrared inspection, keep the following in mind:
Prior to the infrared inspection, obtain drawings with sufficient detail
Verify accuracy of drawings with the subject structure
Obtain a separate plan for each subject floor
During the inspection, mark the location of exceptions directly on
drawings along with thermogram numbers, where appropriate
Whenever possible, obtain extra sets of drawings to be used as file copies or for field use. When utilized properly, floor plan drawings can serve as valuable reference tools enabling everyone to “speak the same language” when it comes to properly referencing locations.