2017
January 02, 2017
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Understanding Radiance
Keeping it simple is a principle for effective communications. When it comes to infrared thermography, oversimplification can be detrimental when it leads to confusion or misunderstandings.
In trying to explain the operation of thermal imagers, many will frequently state that infrared imagers sense temperatures across the surface of objects. While this may allow a layperson to grasp the concept of infrared equipment operation, it can foster a basic misunderstanding that can lead to significant diagnostic errors.
Infrared imagers do not sense temperature. Rather, they directly sense infrared energy radiated from the surface of an object. Using sophisticated on-board computers, radiant energy is converted to a monochrome or multi-colored image that represents the apparent thermal patterns across an object’s surface.
Emissivity is the most significant characteristic influencing the amount of energy radiated by an object. Emissivity is a dynamic phenomenon that is influenced by many factors; the relative amount of energy radiated by an object is described by its emittance.
Emittance is a number between 0 and 1 that numerically expresses how well an object radiates infrared energy when compared to a blackbody at the same wavelength and temperature. The emittance of an object will vary with temperature, shape and surface condition. In thermography, emittance can be further influenced by viewing angle and the spectral response of the imager/radiometer utilized.
In order to ensure accuracy, it is imperative for a thermographer to understand the concepts of radiance and the principles of non-contact temperature measurement. Anything that affects emissivity will influence both qualitative and quantitative data.
For over 35 years, Infraspection Institute’s Certified Infrared Thermographer® training courses have set the industry standard for excellence. Our Certified Infrared Thermographer® and applications courses combine infrared theory with practical, real-world approaches that enable students to quickly master skill sets that help to ensure accuracy. All courses are taught by field-experienced practicing thermographers. For more information or to register for a class, call 609-239-4788 or visit us online at www.infraspection.com.
January 09, 2017
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Why Imagers & Radiometers Disagree
As the awareness of non-contact temperature measurement has increased, spot radiometers have become common tools in the workplace. Discrepancies frequently arise when temperatures taken with spot radiometers are compared to temperatures obtained with an imaging radiometer.
Advances in technology and increased sales volume have allowed several manufacturers of spot radiometers to offer a number of models priced below $100. Lower cost, combined with a greater awareness of infrared thermometry, has allowed most maintenance personnel to incorporate spot radiometers into their toolboxes.
When a thermographer reports temperatures obtained with an imaging radiometer, maintenance personnel will frequently attempt to cross-verify reported temperatures with a spot radiometer. In such situations, discrepancies are common as the spot sizes of imaging radiometers and spot radiometers often vary widely. In order to ensure measurement accuracy and avoid discrepancies, one should bear the following in mind:
- For accurate temperature measurement, radiometers must be operated correctly and in accordance with manufacturer’s instructions
- Radiometer accuracy can degrade over time or with physical stress
- Spot radiometers will generally have spot measurement sizes that are larger than imaging radiometers
- When spot measurement sizes vary between instruments, reliable cross-verification is not possible
To avoid discrepancies, personnel who utilize infrared radiometers should be trained in the proper use of their test equipment along with its limitations. Personnel must also understand how the characteristics of infrared instruments affect the accuracy of observed temperatures. Lastly, using cross-verification of temperatures should be avoided when radiometer capabilities differ from each other.
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January 16, 2017
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Why Building Corners Appear Cool
Tip written by: Infraspection Institute
When performing infrared inspections of framed buildings from the interior, thermographers often note that corners appear at a different temperature. With this Tip we explore the reasons for this condition and how to differentiate potential problems from normal conditions.
Corners are a common construction detail found within building walls that utilize frame construction. Corners are typically constructed with vertical framing members that both support the framed wall and provide a nailing surface for interior paneling or drywall. Although details can vary, a typical corner has three vertical studs in close proximity to each other.
More energy loss occurs at corners for two reasons: Studs are more conductive than insulation; and there is little or no space for insulation to be installed wherever corner framing studs are present. Because of this, it is normal to see greater energy loss at corners when compared to a properly insulated wall cavity.
When performing an infrared inspection of framed walls from the interior of a building with cold outdoor temperatures, corners will typically appear cooler than insulated wall cavities. Observed thermal patterns will reverse should the same inspection scenario exist with warm outdoor temperatures.
When thermographically inspecting corner details, it is normal to observe a straight vertical line from floor to ceiling. This vertical line should be confined to the corner itself and not extend onto the flat wall surfaces adjacent to the corner. Amorphous or geometric thermal patterns appearing within or adjacent to corners should be investigated for cause.
Infrared inspection of building envelopes is one of the many applications covered in the Infraspection Institute Level I Certified Infrared Thermographer® training course. For course schedules or to obtain a copy of the Standard for Infrared Inspection of Building Envelopes, visit Infraspection Institute online at www.infraspection.com or call us at 609-239-4788.
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January 23, 2017
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Infrared Inspection of Load Break Elbows
Tip written by: Infraspection Institute
Load break elbows are a common feature on shielded cables. Thermography may be used to provide evidence of loose or deteriorated connections associated with these connectors.
Load break elbows are insulated plug-type terminals typically used to terminate shielded, underground cables. Load break elbows act as large power plugs for connecting cables to transformers, switching cabinets and bushings equipped with load break receptacle bushings.
Internal to load break elbows are several mechanical connections each of which is subject to deterioration over time. A typical elbow contains a crimp connection and a pin electrode that screws into the elbow. During normal operation, this pin electrode mates with a receptacle which also contains mechanical connections. Elbows and receptacles that have loose or deteriorated connections will operate at elevated temperatures and are readily detectable with a thermal imager.
~ Images courtesy Jim Lancaster
Normally, all electrical connections within an elbow are hidden from view due to the elbow’s molded rubber insulating body. Due to their high emittance, load break elbows are excellent candidates for infrared inspections. In fact, thermal imaging is one of the best ways to inspect these components for the integrity of their connections.
Since line-of-sight access to the electrical connections within load break elbows is not possible, temperatures at the point of origin are likely to be much hotter than observed temperature values on the exterior surface. Small Delta T’s observed on the surface of elbows can be indicative of a serious problem. Because of this, hot load break elbows should be investigated for cause as soon as possible and appropriate corrective measures taken.
Infrared inspection of power distribution systems is one of the many topics covered in all Infraspection Institute Level I training courses. For information on course locations and dates or our Distance Learning Courses, visit us online at www.infraspection.com or call us at 609-239-4788.
January 30, 2017
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Selecting an IR Training Firm
Tip written by: Infraspection Institute
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.
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February 06, 2017
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Why Headers Appear Cool
Tip written by: Infraspection Institute
In business, it is frequently said that cooler heads prevail. When performing infrared inspections of building interiors, window and door headers are often more prevalent.
Headers are a common construction detail found within building walls that utilize frame construction. Headers are horizontal framing members that are typically located at the top of window and/or door openings. In load bearing walls, headers are typically constructed of framing members that are stronger than vertical framing members.
When fabricating headers in wood frame construction, it is common to utilize framing members that are wider than vertical members. These are then often doubled in thickness and placed at the top of the window or door opening. Because headers are typically wider and/or double thickness, there is usually less cavity space for insulation to be installed wherever headers are present. In these circumstances, it is normal to see greater energy loss wherever headers are present when compared to a properly insulated wall cavity.
When performing an infrared inspection of framed walls from the interior of a building with cold outdoor temperatures, headers will typically appear cooler than insulated wall cavities. Observed thermal patterns will reverse should the same inspection scenario exist with warm outdoor temperatures.
For best results, a minimum inside/outside temperature differential of 10ºC is recommended when inspecting buildings with framed wall construction. Proper conduct of infrared inspections is addressed in the Standard for Infrared Inspection of Building Envelopes. Copies of the standard are available through the Infraspection Institute Online Store.
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February 13, 2017
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A Hidden Danger in Electrical Systems
Tip written by: Infraspection Institute
Although thermography is a non-contact test, preparing for an infrared inspection of electrical equipment often requires manual preparation of switchgear components. Unwary thermographers and their assistants can be injured by making contact with cabinets or component surfaces that have become accidentally or unintentionally energized.
Switchgear enclosures and components are generally designed to prevent their surfaces from becoming energized. Under certain circumstances, switchgear enclosures and other dielectric surfaces can become unintentionally energized to significant voltage levels. This potentially lethal condition may be caused by improper wiring, faulty equipment, or contamination due to dirt or moisture.
The image below shows a potential of 265 volts AC between a molded case circuit breaker and ground. This condition was discovered after an unprotected worker received a shock by touching the phenolic breaker handle.
Whenever working on or near energized electrical equipment, keep the following in mind:
- Only qualified persons should be allowed near energized equipment
- Treat all devices and enclosures as though they are energized
- Never touch enclosures or devices without proper PPE
- Do not lean on or use electrical enclosures as work tables
- Always follow appropriate safety rules
- Know what to do in case of an accident
Remember ~
There are old thermographers and
There are bold thermographers; however,
There are no old, bold thermographers.
Thermographer safety is one of the many topics covered in the Infraspection Institute Level I Certified Infrared Thermographer® training course. For more information including course locations and dates, visit Infraspection Institute online or call us at 609-239-4788.
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February 20, 2017
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How to Calculate Emittance
Tip written by: Infraspection Institute
Utilizing correct emittance values is imperative for accurate non-contact temperature measurements. Knowing how to accurately calculate emittance values can help to ensure the accuracy of infrared temperature measurements.
Although thermographers frequently obtain emittance values from published tables, this practice can introduce significant errors. Following the procedure listed below, it is possible to accurately calculate the E value of an object.
Equipment Required:
- Calibrated imaging radiometer with a computer that allows thermographer to input Reflected Temperature and Emittance values
- Natural or induced means of heating/cooling target to a stable temperature at least 10ºC above/below ambient temperature
- Calibrated contact thermometer
Method:
- Place imaging radiometer at desired distance from heated/cooled target. Be certain that target is larger than imager’s spot measurement area. Aim and focus imager on target
- Measure and compensate for Reflected Temperature
- Place imager crosshairs on target
- Use contact thermometer to measure target temperature at location of imager crosshairs. Remove contact thermometer
- Without moving imager, adjust E control until observed temperature matches value obtained in Step 4 above. The displayed E value is the Emittance value for this target with this imaging radiometer. For greatest accuracy, repeat above three times and average the results.
Note: This procedure requires contact with the object being measured. Be certain to observe all necessary safety precautions prior to making contact with target.
The above procedure is described in detail in the Standard for Measuring and Compensating for Emittance Using Infrared Imaging Radiometers. Copies of the Standard are available from the Infraspection Online Store or by calling 609-239-4788.
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February 27, 2017
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How to Calculate Transmittance
Tip written by: Infraspection Institute
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 steps a minimum of three times and average results.
The above procedure is described in detail in the Standard for Measuring and Compensating for Transmittance of an Attenuating Medium Using Infrared Imaging Radiometers available from Infraspection Institute. For more information or to place an order, call 609-239-4788 or visit the Infraspection Online Store.
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The 3 Most Important Questions
Tip written by: Infraspection Institute
Thermal anomalies are not always as obvious as one might expect. Often, subtle thermal differences can be indicative of major problems. Because infrared thermography is a visual inspection technique, its effectiveness relies on the observation skills of the thermographer. Like any visual inspection technique, a thermographer must actively concentrate on the imagery displayed by their thermal imager.
Contrary to popular belief, humans are not inherently effective observers. Because humans tend to be casual in their observations, they frequently overlook subtleties. Whenever imaging, a thermographer’s eyes should always visually scan the monitor left to right and up and down while asking him/herself the following three questions:
1. What am I seeing
2. Why am I seeing this
3. Is this normal/reportable
While this approach may sound cumbersome at first, this practice will soon become instinctive and can help prevent you from overlooking the subtle thermal patterns that can be indicative of serious problems.
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Notice of Copyright
Tip provided by:
Robert J. Incollingo
Attorney at Law
4 Munn Avenue
Cherry Hill, New Jersey 08034
856-857-1500
www.rjilaw.com
Every thermographer should know that an image which bears the symbol © (the letter C in a circle) is claimed to be copyrighted, and be interested to learn that although original infrared images and videos can be registered with the Copyright Office of the Library of Congress, no publication or registration or other action such as placing a notice of copyright on the image is legally required. The maker’s copyright is secured automatically when the image is created and fixed in a tangible copy for the first time. While certain rights flow from registration, it is an optional step, just like placing a copyright notice on the image. The copyright owner can elect to put a copyright notice on his image, but he doesn’t have to, nor does he have to get advance permission from, or registration with, the Copyright Office if he does.
The prescribed form of copyright notice for infrared images and other “visually perceptible copies” should contain all the following three elements:
(1) The symbol © (the letter C in a circle), or the word “Copyright,” or the abbreviation “Copr.”; and
(2) The year of first publication of the work; and
(3) The name of the owner of copyright in the work, or an abbreviation by which the name can be recognized, or a generally known alternative designation of the owner.
Example: © 2017 Infraspection Institute
While the use of a copyright notice is no longer required under U. S. law, it still has importance because it informs the public that your work is protected by copyright, identifies you as the copyright owner, and shows the year of first publication of the copyrighted work. Copyrights generally last for the life of the author plus 70 years, so logically, the year of publication is unimportant in figuring when the copyright expires, but can be relevant in any court battle over alleged infringement. Given these benefits, when you feel your creation deserves protection, you should use a copyright notice and use it correctly.
Bob Incollingo is an attorney in private practice in New Jersey and a regular speaker at Infraspection Institute’s annual IR/INFO Conference.
Training and 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.
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How to Use Spot Size Ratios
Tip written by: Infraspection Institute
With awareness of infrared technology at an all time high, point radiometers have become a common tool in a wide variety of industries. Understanding how to properly apply spot size values is imperative for accurate temperature measurement.
For non-contact radiometers, manufacturers typically supply spot size values. These values are usually expressed as a ratio such as 50:1. Spot size ratios allow one to calculate the minimum target size for a given distance or the maximum distance for a given target size. The formulae for these calculations are as follows:
Distance to Target ÷ Spot Ratio = Minimum Target Size
Example: Using a radiometer with a spot ratio of 50:1, calculate minimum target size at 25″ from a target
Solution: 25″ ÷ 50 = 0.5″
Target Size x Spot Ratio = Maximum Distance
Example: Using a radiometer with a spot ratio of 50:1, calculate maximum distance for measuring a 1″ target
Solution: 1″ x 50 = 50″
It should be noted that non-contact radiometers are subject to minimum focus distances. Prior to using the above formulae, ascertain the minimum focus distance for your radiometer. The formulae contained herein are only applicable at or beyond a radiometer’s minimum focus distance.
Lastly, spot size ratios supplied by manufacturers are frequently quoted at 90% radiance (accuracy) or less. The Standard for Measuring Distance/Target Size Values for Quantitative Thermal Imaging Cameras provides a simple procedure for accurately calculating spot ratio values for imaging radiometers. To obtain a copy, contact Infraspection Institute at 609-239-4788 or visit the Standards section of the Infraspection Online Store.
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Using Voltage Drop Measurements
Tip written by: Infraspection Institute
Accurate confirmation of thermal data is a critical step when performing infrared inspections of energized electrical systems. In this Tip we discuss an advanced verification technique known as a voltage drop measurement.
Loose and deteriorated connections are among the most common defects detected during thermographic inspections of electrical systems. Thermal patterns associated with these defects are characterized by heating at, or adjacent to, mechanical connections within the circuit. Loose connections are frequently found at terminals, lugs, fuse clips and splices.
In most cases, thermographers discovering suspected loose connections will document such hotspots and recommend that the observed exception be investigated and appropriate corrective action be performed. Typically, such investigation is performed at a later time with the circuit de-energized utilizing manual inspection or contact resistance testing.
Another method for confirming loose/deteriorated connections is known as a voltage drop measurement. To perform this test, a digital voltmeter is used to measure voltage across the subject connection with the circuit energized and under load. Loose/deteriorated connections will exhibit an increased voltage drop across the connection due to higher resistance. Observed voltage drop values may then be compared to other similar connections under similar load.
Because voltage drop measurements require contact with energized circuits, this testing should only be performed by qualified persons while observing all necessary safety precautions. Lastly, one should be aware that neither temperature nor voltage drop measurements can predict time of failure for any electrical component. Therefore, suspected loose connections should always be investigated for cause and appropriate corrective action undertaken as soon as possible.
Infrared inspection of electrical distribution systems is one of the many applications covered in the Infraspection Institute Level I Certified Infrared Thermographer® training course. For course schedules or to obtain a copy of the Standard for Infrared Inspection of Electrical Systems and Rotating Equipment, visit Infraspection Institute online at www.infraspection.com or call us at 609-239-4788.
Measuring and Compensating for Reflected Temperature – Part 1
Tip written by: Infraspection Institute
Non-contact thermometry provides a means for rapidly measuring object temperatures. To ensure measurement accuracy, all error sources must be considered and properly addressed. With this Tip, we discuss how to measure and compensate for Reflected Temperature using the Reflector Method.
Unlike contact thermometry, infrared temperature measurement is subject to several error sources. While many are familiar with emissivity, another common error source is reflectivity. In order to compensate for errors due to reflections, imaging and non-imaging radiometers have inputs for entering Reflected Temperature. Depending upon the make and model of the instrument, this control may be referred to as TAM, Ambient Temp, Background, or Reflected Temperature.
Since all real world objects have emittance values of less than 1.0, some infrared energy will always be reflected from a measured object’s surface. The Reflected Temperature feature found on radiometers will mathematically compensate for this error source provided that it has been properly set by the operator.
Listed below are the general steps for measuring and compensating for Reflected Temperature when using an imaging radiometer and a diffuse infrared reflector. A diffuse reflector can be made from a crumpled and re-flattened sheet of aluminum foil that has been wrapped around a piece of cardboard.
- Place imager at desired location and distance from object to be measured
- Aim and focus imager
- Place diffuse reflector in front of, and in same plane as, object’s surface
- With imager’s E control set to 1.0, measure apparent temperature of diffuse reflector
- Conduct procedure three times and average results
- Enter averaged value into radiometer’s Reflected Temperature input
When measuring Reflected Temperature, make certain to maintain a safe distance from any hot or energized targets and observe all necessary safety precautions. When entering Reflected Temperature into your radiometer, be sure to access the proper menu as some imagers have inputs for Reflected Temperature as well as ambient air temperature.
The above procedure is described in greater detail in the Standard for Measuring and Compensating for Reflected Temperature Using Infrared Imaging Radiometers. For more information on infrared standards or thermographer training, call 609-239-4788 or visit us online at www.infraspection.com.
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Measuring and Compensating for Reflected Temperature – Part 2
Tip written by: Infraspection Institute
Non-contact thermometry provides a means for rapidly measuring object temperatures. To ensure measurement accuracy, all error sources must be considered and properly addressed. With this Tip, we discuss how to measure and compensate for Reflected Temperature using the Direct Method.
Unlike contact thermometry, infrared temperature measurement is subject to several error sources. While many are familiar with emissivity, another common error source is reflectivity. In order to compensate for errors due to reflections, imaging and non-imaging radiometers have inputs for entering Reflected Temperature. Depending upon the make and model of the instrument, this control may be referred to as TAM, Ambient Temp, Background, or Reflected Temperature.
Since all real world objects have emittance values of less than 1.0, some infrared energy will always be reflected from a measured object’s surface. The Reflected Temperature feature found on radiometers will mathematically compensate for this error source provided that it has been properly set by the operator.
Listed below are the general steps for measuring and compensating for Reflected Temperature when using the Direct Method.
- Place imager at desired location and distance from object to be measured
- Aim and focus imager
- Estimate angle of incidence and angle of reflection
- Position imager pointing away from target & parallel to angle of reflection
- With imager focused and its E control set to 1.0, measure average apparent temperature of scene using either area measurement or isotherm feature
- Conduct procedure three times and average results
- Enter averaged value into radiometer’s Reflected Temperature input
When measuring Reflected Temperature, make certain to maintain a safe distance from any hot or energized targets and observe all necessary safety precautions. When entering Reflected Temperature into your radiometer, be sure to access the proper menu as some imagers have inputs for Reflected Temperature as well as ambient air temperature.
The above procedure is described in greater detail in the Standard for Measuring and Compensating for Reflected Temperature Using Infrared Imaging Radiometers. For more information on infrared standards or thermographer training, call 609-239-4788 or visit us online at www.infraspection.com.
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Infrared Inspections of Arc Fault Circuit Interrupters
Tip written by: Infraspection Institute
Excess heating is often a sure sign of defective electrical equipment; however, the absence of heat can also be a sign of component failure. In this Tip, we demonstrate how thermal imaging may be used to detect defective Arc Fault Circuit Interrupters.
An Arc Fault Circuit Interrupter (AFCI) is an advanced type of electrical circuit breaker that automatically opens a circuit when it detects a dangerous electrical arc on the circuit it protects. Designed to help prevent electrical fires, an AFCI can sense between electrical arcs caused by defective equipment versus those associated with the normal operation of devices such as light switches.
In order to monitor for dangerous electrical arcing on a circuit, AFCI devices have electronic circuitry built into them. This circuitry can cause the body of the AFCI to run several degrees warmer than ambient temperature. Depending upon the settings of your thermal imager, these devices may show a marked contrast to their surroundings.
When thermographically inspecting AFCI devices, be sure to inspect the line and load side connections at the AFCI device as well as the neutral bus bar connection for the subject breaker. Should you find an AFCI device that is operating close to ambient temperature, it is likely that the internal circuitry has failed making the device incapable of protecting against arc faults. Such devices be further tested and replaced should they be found defective.
Infrared inspection of electrical distribution systems is one of the many topics covered in the Level I Infraspection Institute Certified Infrared Thermographer® training course. For information on thermographer training or to obtain a copy of the Standard for Infrared Inspection of Electrical Systems & Rotating Equipment, visit us online at www.infraspection.com or call us at 609-239-4788.
Determining Maximum Operating Temperature for Motors
Tip written by: Infraspection Institute
Operating temperature can have a significant impact on the service life of operating electric motors. Accurately determining maximum operating temperature for motors is critical for setting temperature limits.
One of the specifications for electric motors is maximum operating temperature. This temperature value is determined by several factors including, but not limited to, the motor’s insulation class. Exceeding the maximum temperature for a motor will shorten the life of the motor’s dielectric materials and will result in decreased service life for the motor.
In order to calculate a motor’s maximum rated temperature, one must know the motor’s ambient temperature rating and its rated temperature rise above ambient. Both of these values are generally found on the motor nameplate located on the exterior of the motor casing.
To calculate a motor’s maximum operating temperature, add the ambient and rated rise temperatures. Their sum is the maximum operating temperature for the subject motor at 100% load.
Example:
- Rated Ambient: 40 C
- Rated Rise: 90 C
- 40 + 90 = 130 C or 266 F
It is important to note that some motors specify insulation class rather than a numeric value for temperature rise. In such cases, it is necessary to know the operating limits for the insulation class of the subject motor.
The Infraspection Institute Standard for Infrared Inspections of Electrical Systems & Rotating Equipment provides temperature limits for several common insulation classes of AC and DC motors. In addition to providing inspection procedures, it also provides temperature limit data for lubricants, bearings and seals. To order a copy of the Standard, call 609-239-4788 or visit the Infraspection online store.
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Tornado Safety
Tip written by: Infraspection Institute
With the onset of warm weather, tornado season has arrived. In an average year, tornadoes in the US cause 80 fatalities and 1500 injuries. Knowing what to do before and during a tornado is crucial for survival.
Tornadoes are nature’s most violent storms. Spawned from powerful thunderstorms, tornadoes can cause fatalities and devastate a neighborhood in seconds. A tornado appears as a rotating, funnel-shaped cloud that extends from a thunderstorm to the ground with whirling winds that can reach 300 miles per hour. Damage paths can be in excess of one mile wide and 50 miles long. Every state is at some risk from this hazard.
Some tornadoes are clearly visible, while rain or nearby low-hanging clouds obscure others. Occasionally, tornadoes develop so rapidly that little, if any, advance warning is possible. The best defense against tornadoes is to be alert to weather conditions and be ready to seek shelter.
Before a tornado, be alert to changing weather conditions.
- Listen to NOAA Weather Radio or to local newscasts for the latest information
- Watch for approaching storms
- Know the danger signs: Dark, often greenish sky; large hail; large, dark, low-lying or rotating clouds; loud roar, similar to a freight train
If you see an approaching tornado or are under a tornado WARNING, seek shelter immediately.
- If you are in a structure, go to a pre-designated shelter area or the center of an interior room on the lowest building level. Get under a sturdy table and use your arms to protect your head and neck. Do not open windows.
- If you are in a vehicle, get out immediately and go to the lowest floor of a sturdy, nearby building or a storm shelter. Mobile homes, even if tied down, offer little protection from tornadoes.
- If you are outside with no shelter, lie flat in a nearby ditch or depression and cover your head with your hands. Beware of flying debris and the potential for flooding.
For more information on tornadoes and tornado safety, visit the NOAA website.
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Building Envelope Inspections – Which Way Do We Go?
Tip written by: Infraspection Institute
Infrared inspections of building envelopes have many uses. Of paramount importance is a logical inspection route that covers all subject areas and provides report data that can be easily followed.
Infrared inspections of building envelopes may be performed to detect evidence of thermal deficiencies and/or latent moisture. Typically, infrared inspections cover the exterior walls, windows, doors, and ceilings or roof of the structure. Depending upon the reason for the inspection, the inspection may be performed from either an interior or exterior vantage point. Regardless of vantage point, complete coverage of all subject surfaces is critical to inspection success.
One method of helping to ensure complete coverage is to begin the inspection at a recognizable reference point such as a main doorway or other easily identified feature. From this starting point, the inspection is conducted for all subject surfaces of the building while moving in a clockwise fashion.
Moving in a clockwise fashion allows a thermographer to move in a logical and predetermined fashion around the building. This practice will work equally well when working from either the interior or exterior of the building. When thermal imagery is recorded to video, clockwise routes can help a viewer to better understand recorded data when viewing the video record at a later time.
The topic of infrared inspections of building envelopes is covered in all Infraspection Institute Level I training courses. For more information on thermographer training or to obtain a copy of the Standard for Infrared Inspection of Building Envelopes,contact Infraspection Institute at 609-239-4788 or visit us online at www.infraspection.com.
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Protecting Yourself in the Sun – Part 1
Tip excerpted from: www.osha.gov
With the height of Summer, many thermographers focus their attention on the discomfort associated with heat and humidity. Those who spend time outdoors should also be aware of the health hazards associated with unprotected exposure to the Sun.
Sunlight contains ultraviolet (UV) radiation, which causes premature aging of the skin, wrinkles, cataracts, and skin cancer. The amount of damage from UV exposure depends on the strength of the light, the length of exposure, and whether the skin is protected. There are no safe UV rays or safe suntans.
Following a few simple tips can help protect you from the harmful effects of UV radiation.
- Cover up. Wear tightly-woven clothing that blocks out light. Try this test: Place your hand between a single layer of the clothing and a light source. If you can see your hand through the fabric, the garment offers little protection.
- Use sunscreen. A sun protection factor (SPF) of at least 15 blocks 93 percent of UV rays. You want to block both UVA and UVB rays to guard against skin cancer. Be sure to follow application directions on the bottle.
- Wear a hat. A wide brim hat (not a baseball cap) is ideal because it protects the neck, ears, eyes, forehead, nose, and scalp.
- Wear UV-absorbent shades. Sunglasses don’t have to be expensive, but they should block 99 to 100 percent of UVA and UVB radiation.
- Limit exposure. UV rays are most intense between 10 a.m. and 4 p.m. If you’re unsure about the sun’s intensity, take the shadow test: If your shadow is shorter than you, the sun’s rays are the day’s strongest.
For more information on this topic or on other workplace safety and health issues, visit www.osha.gov.
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Protecting Yourself in the Sun – Part 2
Tip excerpted from: www.osha.gov
Most people have experienced the discomfort of sunburn at one time or another. Few tend to realize that unprotected exposure to the Sun increases one’s risk of developing skin cancer which can be fatal. Early detection is your first line of defense in treating skin cancer.
Sun exposure at any age can cause skin cancer. Be especially careful in the sun if you burn easily, spend a lot of time outdoors, or have any of the following physical features:
- Numerous, irregular, or large moles
- Freckles
- Fair skin
- Blond, red, or light brown hair
It’s important to examine your body monthly because skin cancers detected early can almost always be cured. The most important warning sign is a spot on the skin that is changing in size, shape, or color during a period of 1 month to 1 or 2 years.
Skin cancers often take the following forms:
- Pale, wax-like, pearly nodules
- Red, scaly, sharply outlined patches
- Sores that don’t heal
- Small, mole-like growths – melanoma, the most serious type of skin cancer
If you find such unusual skin changes, see a health care professional immediately. For more information about preventing, detecting, and treating skin cancer, check out these sources:
American Cancer Society www.cancer.org
Centers for Disease Control and Prevention www.cdc.gov/ChooseYourCover
The Skin Cancer Foundation www.skincancer.org
For more information on this topic or on other workplace safety and health issues, visit www.osha.gov.
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Does Thermography Really Save Time and Money?
Whether you work as a professional thermographer or are setting up an in-house infrared inspection program, it is important to accurately represent the benefits of thermography to prospects or peers. Failure to do so can lead to unrealistic expectations and disappointment.
The statement, ‘Thermography saves time and money’ is a popular phrase associated with our technology; however, it is a fallacy. As a practice, thermography alone saves neither time nor money. This is due to the fact that infrared inspections require time for their planning and execution, both of which come with a cost. Furthermore, correcting detected exceptions will require additional time and money.
When listing the benefits of thermography, it is important to accurately represent the benefits of the technology in order that others may set their expectations appropriately. This is especially important when seeking approval for in-house programs in order that they may be appropriately funded and staffed.
To this end, an alternative to the aforementioned statement might be:
Combined with timely, effective repairs, thermography can help to save time and money by reducing unscheduled downtime or premature failures.
Setting up an infrared inspection program is one of the many topics covered in the Level I Infraspection Institute Certified Infrared Thermographer® training course. For information on thermographer training or to register for a class, visit us online at www.infraspection.com or call us at 609-239-4788.
Warm Lighting Circuit Breakers
Tip written by: Infraspection Institute
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.
Infrared inspections of power distribution systems is one of the many topics covered in the Level I Infraspection Institute Certified Infrared Thermographer® training course. For information on thermographer training including course locations and dates, visit us online at www.infraspection.com or call us at 609-239-4788.
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Infrared Training – Why it Isn’t All the Same
Tip written by: Infraspection Institute
With interest in thermography at an all-time high, more people are seeking training and certification. When comparing infrared course offerings, many mistakenly assume that all training and certification courses are the same.
The greatest limitation in an infrared inspection is the thermographer. Because of this, thermographer training and certification have long been recognized as requirements to help ensure accurate inspections. To this end, several firms offer Level I, II, and III training courses; however, these courses are not equal.
The American Society for Nondestructive Testing document, SNT-TC-1A outlines suggested topics for training and certifying NDT personnel in the Thermal/Infrared Testing Method. Suggested topics range from basic theory and camera operation to advanced thermographic applications. Since these topics are suggestions, companies have wide latitude in compiling course content. Because of this, one should never assume that courses bearing the same name will contain similar content.
When considering any infrared training course, be certain to:
- Review course curriculum carefully to ensure it meets your needs
- Ascertain type of certification provided and its expiration date
- Consider the history of the training firm and its credentials
Lastly, beware of training courses offered by equipment manufacturers or “vendor neutral” instructors. Only an independent training firm can offer unbiased opinions with respect to equipment choices.
For over 35 years, Infraspection Institute’s Certified Infrared Thermographer® training courses have set the industry standard for excellence. In addition to our Level I, II, and III Certified Infrared Thermographer® courses, we offer several industry-specific application and operator training courses. All courses are taught by field-experienced Level III practicing thermographers. For more information or to register for a class, call 609-239-4788 or visit us online at www.infraspection.com.
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Using Tmax Corrected Formula to Prioritize Electrical Exceptions
Tip written by: Infraspection Institute
For decades, temperature measurement has been used to gauge the operating condition of electrical components. With this Tip, we explore an alternative to the traditional Delta T method of prioritizing exceptions during infrared inspections of electrical distribution systems.
Thermographers have long used temperature differentials or Delta T measurements as a means of prioritizing electrical exceptions. Typically, Delta T values are calculated by comparing the temperature of an exception to similar components under similar load or to ambient air temperature. Although they work well in many circumstances, Delta T readings are not applicable for components that do not qualitatively manifest themselves as an exception.
An alternative to Delta T calculations is a formula known as Tmax Corrected. This formula is based upon an IEEE formula and calculates pass/fail criteria based upon several factors including equipment type, ambient air temperature, and circuit load. The Tmax Corrected formula looks like this:
TmaxCorr = {(A meas ÷ A rated )2 (T rated rise)} + Ambient
Where:
- Tmax Corr = corrected maximum allowable temperature
- A meas = measured load, in amperes
- A rated = rated load, in amperes
- T rated rise = rated temp rise for component
- Ambient = measured ambient temp
It should be noted that the exponent can vary between 1.6 to 2.0. In this Tip, we have shown an exponent of 2 for simplicity.
Despite taking a little more time to apply than Delta T calculations, Tmax Corrected allows one to determine if a component of interest is running within specification for any load or ambient temperature. Tmax Corrected is especially useful for equipment that is not manifesting itself as an exception. In particular, Tmax Corrected can be an invaluable tool for those who perform infrared inspections as part of commissioning studies or use thermography for acceptance testing of new installations, repairs, or retrofits.
Proper use of the Tmax Corrected formula is just one of the many topics covered in all Infraspection Institute Level II Certified Infrared Thermographer® training courses. The proper application of Tmax Corrected along with a comprehensive table of rated temperature rises is also detailed in the Standard for Infrared Inspection of Electrical Systems and Rotating Equipment. Copies of this Standard may be purchased by calling 609-239-4788 or through the Infraspection Online Store.
