Have you ever wondered what the size of your imager’s field of view is at a given distance? If you know the visual field of view specifications for a thermal imager, it is possible to calculate the size of your imager’s viewing area for any given distance using a scientific calculator. The formula for this calculation is:

{(tangent 1/2 viewing angle) x distance} x 2

To apply the above formula, follow these steps:

1. Determine your imager’s Field of View (in degrees) from the manufacturer’s specs.

2. Divide the value from Step 1 by 2

3. Use scientific calculator to determine tangent of number obtained in Step 2

4. Multiply number in Step 3 by distance from imager lens to object.

5. Multiply number in obtained in Step 4 by 2. This will be the width of the imager’s field of view at the specified distance.

Example: Calculate field of view for 16° lens at 25’.

(tan 8° x 25’) x 2 =

(0.140541 x 25’) x 2 =

(3.513525’) x 2 = ˜ 7.0’

If your imager specifies different Field of View values for horizontal and vertical, it will be necessary to calculate each value separately. Calculated values should be used for estimation purposes as actual values may vary slightly.

When performing infrared inspections of electrical distribution systems, many people identify the individual phases of polyphase circuits as A, B, and C; others frequently use 1, 2, and 3.

Confusion can arise with alphabetical or numerical labels particularly when switchgear enclosures are inspected from different perspectives e.g. front versus rear. Further confusion can occur when phase rotation has been modified or changed or, in some cases, mislabelled.

Reference errors can be avoided by using terms that cannot be confused such as Left, Middle, Right OR Upper, Middle, Lower. When using such terms, one should always reference where the image was taken from. For outside power lines references such as Street, Center, and Field may be used to identify phases without confusion.

Using the above simple terms can make your reports easier to understand and help to eliminate confusion when repairs are performed.

Thermal imging can often be used to help locate leaks from pipelines buried within concrete. For best reults, the subject piping should be heated as much as possible prior to imaging. Cold water lines may be heated by continuously flushing them with hot water. The amount of time required will depend upon the burial depth of the lines and the thermal conductivity of the concrete.

Once the lines have been heated, use your thermal imager to inspect the pathway of the pipe. Pipe leaks will appear as amporphously shaped warm areas instead of the well-defined lines caused by the pathway of the pipe. Suspected leaks may be marked directly on the concrete to direct excavation efforts required for leak verifcation and repair.

When imaging outdoors, it is best to perform infrared imaging at night to avoid interference from the sun.

Translated from tip submitted by Juan Nava, Cemex Mexico Planta Hermosillo.

Gracias Juan!

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.

Traditionally, storage batteries for thermal imagers have been proprietary and available only from the imager manufacturer. Often, these special battery packs have cost hundreds of dollars each.

With a moderate amount of electrical skill and some homework, there are affordable power alternatives to be found in commercially available battery packs. To use an alternative battery, do the following:

1. Determine the required voltage of your imager.

2. Use a DC ammeter to determine the imager current requirements. If you know your imager’s power consumption in Watts, divide this number by the voltage required by your imager. Example: An imager that uses 12 Watts at 6 volts will draw 2 amps of current.

3. Select a battery with appropriate voltage and capacity. To determine how a battery will last with your imager, divide the Amp Hour rating by the current draw of your imager. A wide variety of rechargeable batteries are available through many professional video retailers.

4. Construct a fused power cord to connect your imager to your power supply making sure that the polarity is correct.

Constructing your own battery packs can save you money and result in longer run times between battery charges.

Proper planning prevents poor performance. This frequently repeated phrase has been applied to many disciplines and has application in thermography as well. One of the greatest appeals to thermography as a PdM tool is the wide range of potential applications. However, without planning the varied uses for thermography can cause one to lose focus and compromise program efficiency.

Using preplanned routes can improve inspection efficiency by serving as a roadmap for your inspection activities. When setting up inspection routes, keep the following in mind:

1. When possible, use established routes from other PdM technologies such as vibration analysis.

2. Routes should be of same class or hierarchy for subject equipment. As an alternative, establish routes based upon physical location.

3. Keep in mind requisite travel times between locations.

4. Establish routes to ensure that subject equipment will be under proper load.

5. Never include more equipment in a route than can be accomplished in a single work shift.

When following a route during an inspection, any equipment not inspected should be noted in the final project report.

Everyone has heard the fabled race between the tortoise and the hare in which the tortoise beats the hare. One of the morals of the story is that a steady pace may be more fruitful than erratic bursts of speed.

Thermographers who perform infrared inspections should keep in mind that a slow and steady pace can lead to victory. Working at an even pace can help to prevent overlooking the subtle temperature variations that often indicate serious problems. Purchasers of thermographic services should bear in mind that the best value is not in the fastest inspection time, but rather in the thoroughness and accuracy of the inspection.

When it comes to your next infrared inspection, beware of the hare. Inspections that are praised more for their swiftness today may be cursed in the future for their costly oversights.

Nearly all portable thermal imagers designed for predictive maintenance utilize storage batteries as a power source. As such, even the best thermographers are limited by the storage capacity of their batteries. When planning a project it is helpful to know how long your batteries should last.

Most batteries sold are rated in Amp Hours, a number used to indicate battery supply capacity. To determine how long a battery will last with your imager, divide the Amp Hour rating of the battery by the current draw (in Amps) of your image. For an imager that draws 2 Amps, a 6 AH battery will last 3 hours.

Depending upon their size, some batteries are rated in milliAmp Hours. To convert this number to Amp Hours, divide the mAH rating by 1000. Example: An 1800 mAH battery equals 1.8 AH

It is important to know that some imagers consume more power during start up. If so, this will shorten the expected run time of a battery from the calculation above. A battery’s storage capacity also decreases with age. If your batteries are providing extremely short run times, it may be time to replace them with new ones.

If you have inactive spots on the LCD screen in your infrared camera's monocular viewfinder, they are probably caused by sun damage.

When working outdoors, sunlight can easily enter an upturned viewfinder eyepiece. When this happens, sunlight can be magnified by the viewfinder optics permanently damaging or destroying your LCD screen.

To prevent such damage, always cover your imagers eyepiece to prevent sunlight from entering the viewfinder. Temporarily placing a cover such as a baby sock over the eyepiece until you are ready to image can help to avoid a ruining an expensive viewfinder.

Submitted by James Henry,
IMC Chemicals

If you are a thermographer who performs infrared inspections of electrical distribution systems, you are not alone and you never should be. Working alone near exposed, energized electrical equipment is not only dangerous, it is a violation of federal law!

Administered by OSHA, the Occupational Safety and Health Standards for General Industry, 29 CFR, Part 1910 apply to most thermographers working within the United States or its territories. Specifically, 1910 Subpart R covers the operation and maintenance of electric power generation, control, transformation, transmission and distribution lines or equipment. Covered facilities include utilities and equivalent industrial establishments.

According to Subpart R, prior to the commencement of work, medical and first aid supplies must be provided for, including persons trained in first aid and CPR when work is on or near exposed lines or equipment energized at greater than 50 volts. Since CPR cannot be self-administered, at least two people trained in first aid and CPR must always be present when working near most exposed energized equipment.

When performing infrared inspections in the future, having a second CPR trained person along will not only satisfy OSHA requirements, it may save your life should an accident occur!

A specification commonly provided for thermal imagers is Instantaneous Field of View or IFOV. Many people mistakenly believe that IFOV values provide meaningful information about a thermal imager’s performance. Unfortunately, this is simply not true.

Originally developed for evaluating the optical performance of thermal imaging systems, IFOV values were intended to allow a user to calculate the minimum target size needed to achieve 50% probability of detection at any given distance. Using IFOV values to evaluate modern thermal imagers and radiometers is unreliable for several reasons:

1. To date, there is no accepted standard for determining IFOV. Consequently, imager manufacturers calculate IFOV values differently, making test results impossible to compare.

2. Because IFOV values are reported for a single pixel, they cannot be used to accurately calculate spot measurement size for imaging radiometers since accurate temperature measurement requires several pixels, not just one.

3. Stated IFOV values are traditionally reported at 50% radiance or less which is unreliable for both temperature measurement and accurate thermal imaging.

When comparing commercial infrared equipment specifications, one should simply ignore IFOV values and concentrate on meaningful specifications instead.

While it is often interesting to use a thermal imager to view ordinary objects, imaging the sun, arc welders and similarly hot objects should be avoided unless your imager has been built specifically for these applications. The reason for this is that the sensitive thermal detector that comprises the heart of any thermal imaging system can be destroyed by imaging very hot objects, even for brief periods of time.

To help avoid a costly detector replacement, only image objects whose temperatures are within the stated operating range of your imager.

Perhaps a sage corollary could be derived from Bruce Springsteen's epic song, Blinded by the Light:

... Mama always told not to image into the sights of the Sun...

A ruined detector assembly is NOT where the fun is.

Almost all handheld thermal imagers come equipped with neckstraps as standard equipment. If you utilize the neckstrap supplied with your imager to support or carry your imager, the following tips can help to avoid costly damage caused by an unexpected drop.

1) Many neckstraps are made of relatively thin material. Retrofit thin neckstraps with sturdier material.

2) Check your neckstrap frequently for wear. Neckstraps frequently become frayed where they attach to camera body eyes or snap hardware.

3) Be certain that your neckstrap ends are permanently sewn so that they cannot be pulled apart or separate accidentally.

4) Check snap swivels for condition. Replace worn or inferior hardware with quality materials.

5) Consider adding a second, redundant neckstrap in case the primary neckstrap fails.

6) Periodically check camera body eyes for wear and mechanical integrity. Over time, attachment points that mate with metal hardware can erode; mechanically fastened hardware on your imager can become loose.

Following the above tips can help prevent accidentally dropping your imager and could save you from a costly repair.

Over the past twenty years, a number of temperature severity guidelines that have been published by various organizations. When using these guidelines, you may compare similar components under similar load to each other OR compare the subject component to ambient. The former of these approaches is recommended since since ambient temperature can swing widely over time. Furthermore, it is often impossible to obtain an accurate ambient temperature for devices located within an enclosure once the enclosure has been opened for the infrared inspection.

One of the most conservative temperature guides can be found in the Maintenance Testing Specifications, published by the National Electrical Testing Association, Morrison, Colorado. According to the NETA MTS, temperature differentials greater than 15° C are categorized as, "Major discrepancy; repair immediately".

Other organizations publish less conservative temperature guidelines than the NETA MTS. Some guides require delta T's of 70°C or higher to qualify as items of immediate concern. When setting temerature limits, one should remember that temperature differentials cannot be utilized to predict time to failure for an electrical device. Therefore, all thermal anomalies detected during an infrared inspection should be investigated and proper corrective measures undertaken as soon as possible.

Capacitors are devices commonly found in AC electrical distribution systems where power factor correction is required. Like any electrical component, capacitors need to be regularly checked for proper operation. Infrared thermography can be used to rapidly inspect capacitors from a safe, remote distance.

Capacitors are wound devices that are electrically connected between potential and ground. Capacitors used for power factor correction are generally encased in painted, rectangular steel canisters and often have two equal sized bushings for electrical connections. In a three phase circuit, there may be several capacitors connected to each phase.

The most common failures of capacitors are loose/deteriorated bushing connections, open circuits due to internal winding failure, and open supply circuits. When inspecting capacitors, be sure to:

1. Visually inspect capacitor bodies. Capacitors should not be misshapen/ swollen.

2. Thermographically inspect capacitor bodies. Capacitors should be warmer than ambient air temperature and exhibit equal temperatures across all phases.

3. Check bushing and wiring connections for hotspots.

Any thermal anomalies detected should be investigated and corrected as soon as possible. Capacitors operating at ambient temperature should be corrected immediately as imbalanced capacitance can be more detrimental than having no capacitors at all.

Everyone who has performed infrared inspections outdoors on sunny days is familiar with the problem of solar reflections. Compensating for solar reflections is usually accomplished by repositioning the thermal imager to change the viewing angle to eliminate the reflection. For objects exposed to strong sunlight, a more insidious problem can occur in the form of solar loading.

The concept of solar loading is familiar to everyone: objects exposed to the Sun will heat up. In general, dark colored objects absorb the most solar energy and heat faster than light colored objects. If an object absorbs enough heat from the Sun, significant thermal anomalies may be hidden and go undetected.

As there is no way to compensate or correct for solar loading, the most prudent course of action is avoidance. Solar loading can be avoided by imaging on cloudy days, at night, or early in the morning. Solar loading can also be overcome by shading an exposed target and waiting for the object’s temperature to return to normal.

Capacitors are devices commonly found in AC electrical distribution systems where power factor correction is required. Like any electrical component, capacitors need to be regularly checked for proper operation. Infrared thermography can be used to rapidly inspect capacitors from a safe, remote distance.

Capacitors are wound devices that are electrically connected between potential and ground. Capacitors used for power factor correction are generally encased in painted, rectangular steel canisters and often have two equal sized bushings for electrical connections. In a three phase circuit, there may be several capacitors connected to each phase.

The most common failures of capacitors are loose/deteriorated bushing connections, open circuits due to internal winding failure, and open supply circuits. When inspecting capacitors, be sure to:

1. Visually inspect capacitor bodies. Capacitors should not be misshapen/ swollen.
2. Thermographically inspect capacitor bodies. Energized capacitors should be warmer than ambient air temperature and exhibit equal temperatures across all phases.
3. Check bushing and wiring connections for hotspots.

Any thermal anomalies detected should be investigated and corrected as soon as possible. Capacitors operating at ambient temperature should be corrected immediately as imbalanced capacitance can be more detrimental than having no capacitors at all..

We’ve all heard the phrase, “A chain is only as strong as its weakest link.” When it comes to thermography, the weakest link is frequently not the test equipment but rather the thermographer.

All too often, many facility managers are led to believe that infrared imagers are fully automatic instruments that require nothing more than “point and shoot” operation. While thermography is a science, it is also an art or craft requiring a skilled human operator for both conducting the inspection and interpreting the data obtained.

In order to achieve maximum effectiveness, thermographers need to have an understanding of infrared theory, heat transfer concepts, equipment capabilities and limitations, and environmental conditions, as well being knowledgeable about the system(s) being inspected.

Whether you are setting up an infrared inspection program or maintaining one, thermographer training should not be overlooked. Obtaining quality training is an investment that can pay huge dividends by maximizing the effectiveness of thermographers and eliminating your weakest link.

Infraspection Institute offers Level I, II, and III training and certification for thermographers worldwide. Our infrared training programs meet the requirements for training of NDT personnel in accordance with the ASNT document, SNT-TC-1A.

With onset of warmer weather, the harshness of winter is but a fading memory for most. Left undetected, the damage caused by winter’s fury is a reality that can lead to premature roof failure. Fortunately, an infrared inspection of your roof can detect evidence of problems before they can get out of hand.

Performed under the proper conditions with the right equipment, an infrared inspection can detect evidence of latent moisture within the roofing system often before leaks become evident in the building.

The best candidates for infrared inspection are flat or low slope roofs where the insulation is located between the roof deck and the membrane and is in direct contact with the underside of the membrane. Applicable constructions are roofs with either smooth or gravel-surfaced, built-up or single-ply membranes. If gravel is present, it should be less than ½” in diameter and less than 1” thick.

For smooth-surfaced roofs, a short wave (2-5.6 µ) imager will provide more accurate results especially if the roof is painted with a reflective coating. All infrared data should be verified by a qualified roofing professional via core sampling or invasive moisture meter readings.

Thermography is a versatile nondestructive test technique that has a wide variety of applications. In short, thermography can be applied to any situation where knowledge of heat patterns and associated temperatures across a surface will provide meaningful data about a system, object, or process.

In thermography, there are two basic approaches to evaluating data. Qualitative thermography or thermal imaging relies on observing thermal patterns and noting any inexplicable differences or anomalies. Quantitative thermography adds non-contact temperature measurements to thermal images.

Many systems produce heat as a byproduct of operation. Such systems include electrical distribution systems, machinery and insulated structures. These systems are generally inspected during normal operation once line-of-sight access is obtained.

Thermography can also be applied to systems that do not produce heat as a byproduct of operations by actively heating and/or cooling the target and observing the resulting images. Systems that are candidates for active thermography include building facades, low slope roofing systems, storage tanks and composite materials.

When heated or cooled properly, thermal patterns caused by changes in the thermal conductivity or capacitance of the subject system can provide evidence of internal structures, water infiltration, or contaminants. The use of active thermography is growing, especially for inspection of composite materials used in the aircraft, aerospace, and marine industries.

One of the most frequently asked questions in thermography is, “How close do I need to be to my target?” The answer depends upon target size and the type of data that are desired.

Appropriate distance is largely dependent upon three factors: target size, IR equipment optics, and detector resolution.

With qualitative thermal imaging, the maximum viewing distance is achieved where the object and any possible anomalies can be clearly resolved. If a target cannot be clearly distinguished, it will be necessary to move closer or to use a telephoto optic.

When using an imaging radiometer, obtaining accurate temperatures will require substantially shorter distances than those required for thermal imaging. Obtaining accurate quantitative data requires that the radiometer’s spot measurement size is smaller than the area being measured. If it is determined that the radiometer’s spot size is larger than the area being measured, it will be necessary to move closer or use a telephoto optic calibrated for the imager.

Because there is no method for correcting for errors caused by imaging at excessive distances from a target, it is imperative to always ensure appropriate distance prior to recording images.

Many facilities undergo regularly scheduled shutdowns for preventive maintenance. Performed prior to shutdowns, infrared inspections can help to point out potential problems in electrical and mechanical systems and allow for more effective use of resources during a shutdown.

When planning a scheduled outage, it is a good practice to schedule infrared inspections four to six weeks prior to the outage. Doing so can uncover hidden problems and allow for scheduling of additional requisite manpower and/or obtaining replacement parts prior to the shutdown. Infrared inspections can also save money by helping to direct maintenance efforts where they will be most needed during the planned outage.

Pre-outage infrared inspections should be performed with subject equipment energized and operating under normal load. Inspections should be performed by trained and certified thermographers who are familiar with the equipment being inspected.

A follow-up infrared inspection of all repaired/retrofitted equipment should be performed within 48 hours of repair or installation to confirm that repairs were effective.

For more information on training and certification, or to obtain a copy of the Guideline for Infrared Inspection of Electrical and Mechanical Systems, please contact Infraspection Institute at 609-239-4788 or visit us online at www.infraspection.com.

When performing an infrared inspection, obtaining quality data relies on the use of proper equipment, thermographer training and knowledge of the system being inspected. It is imperative that a thermographer be familiar with the construction and operation of the object(s) to be imaged before the inspection begins.

Prior to performing an infrared inspection of an object for the first time, a thermographer should:

1. Become familiar with system construction by reviewing appropriate drawings or blueprints noting insulation materials located on, or within, the subject system and how they might impact findings.

2. Discuss with the end user the reason(s) for conducting the infrared inspection.

3. Review any previous inspection reports and operational data to determine history of the subject system including past problems.

4. Ascertain that the system is under normal operating conditions and how its operation is likely to affect thermal signatures.

5. Ensure that line-of-sight access is available and that environmental conditions and infrared equipment are appropriate for collecting accurate data.

6. Determine if a similar system is available for reference purposes.

Following the above can vastly improve the quality of collected data and help to reduce errors in reporting. As always, remember to work safely.

With most thermal imagers capable of displaying images in monochrome or multicolor, many new thermographers ask which color palette is the best choice for effective imaging. The answer will depend on a number of factors including application, delta T associated with the exception, and personal preference.

Because it is usually less confusing than multi color palettes, grayscale may be better suited for some applications. Additionally, applications that have a large delta T associated with exceptions or where target recognition is important may be better suited for grayscale imaging. Such applications include electrical distribution systems, building envelopes inspected from the interior of the structure, and low slope roof inspections.

Multicolor palettes offer an advantage when imaging targets having a small delta associated with exceptions or when imaging targets with several discrete temperature zones. Typical applications include mechanical systems, refractory systems, building envelopes inspected from the exterior, and medical/veterinary applications.

For hardcopy reports, printing monochrome images can result in lower cost than multicolor reports. Lastly, the choice to use monochrome or multicolor is largely a matter of personal preference. Thermographers should always use a palette which best represents the observed thermal patterns and provides data that are easily understood.

With tremendous emphasis placed upon the sophistication of today’s modern thermal imagers, it’s easy to forget the basics of thermal imaging. Regardless of imager age or sophistication, there are several basic concepts that can vastly increase the accuracy and success of an infrared inspection.

1. Select the proper spectral response imager for the application.

2. A clear line of sight to the target is required with no obstruction of the imager lens.

3. Imager optics must be clean and calibrated to the imager being used.

4. Target should be dry and at a stable temperature.

5. Imager focus is imperative to accurate diagnosis and temperature measurement. Be sure to focus imager and the viewfinder as well.

6. Knowing the construction, operation and characteristics of the system being inspected is vitally important to anticipating thermal patterns and performance.

7. Adverse atmospheric conditions such as wind, humidity, or solar reflection and solar loading should be avoided.

8. For electrical and mechanical equipment, the systems must be energized and under load; for structural inspections, a delta T of 10 C (18 F) is desired.

9. Discriminating small temperature differentials across targets with low emittance values can prove quite difficult.

10. Whenever safely possible, cross reference observed infrared temperature values with accurate contact temperature readings.

When performing any infrared inspection, be certain to take all necessary safety precautions and always work safely..

With the advent of digital storage media, nearly every modern thermal imager is capable of storing images electronically. For thermal imagers that do not have image storage capability, there are inexpensive and readily available solutions.

For thermal imagers having a video output jack there are two options for image storage. The first option utilizes a VCR to record desired imagery. Videotape allows for recording of moving objects and/or dynamic processes. Videotape is inexpensive, readily available, and special equipment is not required for playback. Still images can be captured from videotape using a video capture board available for most personal computers.

The second option utilizes a digital recorder that accepts a standard video input. With a digital recorder, single frames of data may be captured to digital media such as PC cards. Camcorders having a digital snapshot camera feature may provide the best solution of all. Several currently available models allow a thermographer to record to videotape and/or to capture still images from the video input. Additionally, the daylight snapshot feature of the camera may be used to capture high quality daylight images.

Once images have been recorded, they can be directly imported into a PC for storage or incorporation into written reports

When it comes to providing a stable platform for a thermal imager, it’s hard to beat a tripod. As thermal imagers have gotten smaller and lighter, many thermographers have all but forgotten this once requisite accessory that can help provide better quality data while reducing stress.

For many PdM applications that require still images only, using a thermal imager in a hand held configuration is usually sufficient. However, for applications that require imaging from a fixed vantage point over extended periods of time or where videotaping is desired, a tripod can be an invaluable accessory. When selecting a tripod there are several things you should bear in mind:

1. Be sure to select a tripod capable of carrying the weight of your imager.

2. Tripods should connect directly to the imager via a 1/4” x 20 set screw. Tripods with plastic quick releases should be avoided as they are subject to wear and can cause an imager to suddenly fall.

3. Tripods with sturdy hardware and locking systems are more secure and generally last longer than inexpensive models.

4. Fluid head tripods are preferable since they provide smooth motion for videotaping and are less likely to drop an imager if the head is left unlocked.

When carrying a tripod be sure to maintain a safe distance from energized electrical equipment or moving machinery.

For many facilities, obtaining accurate product level information for tanks and silos is critical for effective inventory management and safety. Under the right conditions, a thermal imager can quickly indicate product levels and serve as a cross reference for calibrating level indicators.

When product is stored in a vessel, the density of the product is usually greater than the head space of air or gas above the stored product. For stored products that generate heat, levels may be observed by imaging the vessel’s exterior and noting the temperature gradient between head space and product.

For stored products that do not generate heat, it is possible to rely on solar loading to create a temperature differential. Under solar loading conditions, vessels will usually exhibit cooler temperatures above the product level during the early to mid morning hours. As the day progresses, the head space will exceed product temperature and show as a warm area above the product. This thermal pattern may remain for up to several hours after sunset and reverses once the head space cools to below stored product temperature.

In general, this application works best for un-insulated vessels having a high emittance. For vessels with a low emittance, it may be possible to modify the surface with a stripe of high emittance paint.

Electrical bus ducts are a common feature found in many commercial and industrial electrical systems. When used to supplement regular PM, infrared inspections can help to detect loose or deteriorated connections that can lead to costly catastrophic failures.

Electrical bus ducts are used to distribute low voltage power throughout many industrial facilities. Modern bus ducts are unitized structures that contain insulated conductors within a steel casing. Individual sections of bus duct, each typically 10 feet long, are joined with bolted connections at the end of each bus section. Published industry standards recommend that bus duct connections be manually tightened every six months.

Even with regular tightening of bus duct connections, loose/deteriorated connections are difficult to detect. With the bus duct under load, a thermal imager can readily detect the temperature differentials associated with loose connections. Properly functioning bus ducts should exhibit no temperature differential in the vicinity of bolted connections. Because bus duct conductors are hidden from direct line of sight, any inexplicable temperature differentials should be investigated and corrected immediately. Disconnect switches and cable connections should be checked for thermal anomalies as well.

To ensure complete coverage, bus duct should be inspected from both sides of the duct along its entire length. Termination cabinets should also be inspected once the covers have been removed. Annual or semi annual infrared inspections performed by certified, experienced thermographers should be used to supplement regular bus duct maintenance.

Concrete Masonry Unit (CMU) walls are a common construction detail frequently used in single –story and low rise commercial block wall construction. An infrared imager can be used to quickly perform quality assurance inspections of reinforcing grout details which are critical to the strength of finished CMU walls.

During the construction of CMU walls, concrete grout is used to fill the cavity spaces of the blocks in order to provide structural integrity. Vertical details extending from the foundation to the top of the wall are usually placed at regularly spaced intervals along the length of the wall. Reinforcing grout is also placed around openings for doors and windows or in areas where wall extra strength is required.

Because grout details change the thermal capacitance and conductance of the wall, temperature differentials will occur wherever grout details are present. Infrared inspections may be performed under solar loading, heat loss, or cooling conditions depending upon local climate and time of day. Properly installed grout details will appear as uniformly cool or warm unbroken lines in the subject wall areas according to time of day and whether the inspection is performed from the interior or exterior of the building.

UPS systems and emergency generators are common defenses for facilities where uninterrupted electrical power is critical. Performed properly, IR inspections can help to improve reliability of emergency power systems.

Most facilities perform IR inspections of their electrical distribution systems at least annually as part of a PM program. To help ensure maximum reliability, regularly-scheduled IR inspections should also include the emergency power systems as well. When performing infrared inspections of emergency systems be sure to:

• Inspect all backup generators while running. Begin inspection at generator output leads and proceed to generator bus, breakers, and switchgear.
• Include all Automatic and Manual Transfer Switches. Inspect switches in both normal and emergency positions.
• Inspect UPS system controls, switchgear, battery cells, battery bus and wiring. Battery cell temperatures should be the same between cells with no hotspots on individual cells.
• Have adequate load on the subject emergency circuits This may be accomplished with normal facility load or by utilizing a load bank.

Taking the time to properly include your emergency power equipment in your IR inspection program can pay huge dividends by increasing the likelihood that your backup equipment won’t leave you in the dark should the power fail.

Proper image focus is still one of the most important aspects of performing an infrared inspection. A clear image not only allows for optimal problem diagnosis, but it is also critical to accurate temperature measurement.

Clear focus is not difficult to achieve if you follow a few simple steps:

• 1. Get as close as safely possible to your target
• 2. Take time to carefully focus for optimum clarity. This may take some practice if you have a motorized focus mechanism.
• 3. Ascertain that your target is stationary.
• 4. Only shoot from a stable platform. If imaging from a motor vehicle, it may be desirable to shut off the engine to avoid vibration.
• 5. Be sure your imager is steady as you capture the image. Gently push the store button rather than punching it.
• 6. If using a handheld imager, consider using a tripod or monopod to help stabilize your imager.

Once you’ve stored an image, recall and check for clarity. If the results are less than perfect, start over. In addition to greater accuracy, capturing clear images makes it easier to convey information to the end user and/or the person who will eventually perform corrective actions.

Seasoned professionals know the value of spare parts when it comes to facility maintenance. The principle of always being prepared can be successfully applied to an infrared inspection program as well.

Like any electrical or mechanical device, thermal imaging systems are subject to wear and tear. Having user-replaceable spare parts on hand can help prevent unscheduled downtime for your infrared inspection program. Building a spare parts inventory is easy if you follow a few simple steps:

1. Examine your equipment for parts that are subject to physical wear such as eyepieces, switch covers or hand/neck straps.

2. Identify which parts are fragile and are most likely to break such as viewfinders or external monitors.

3. Determine which items are critical to operation such as power/video cables, batteries, fuses, screws and external hardware.

4. Inventory items which are easily misplaced such as lens caps and flash cards.

5. Purchase necessary items as soon as possible to ensure availability of specialty or custom parts. For critical items, be sure to purchase extras.

6. Replace spare parts when utilized to maintain inventory.

After building your spare parts inventory, keep mission-critical components in a safe place or with your imager so that you will have them when needed.

Unknown emittance values are often the greatest error source when taking infrared temperature measurements. This error source can be eliminated by modifying a target with a material having a known E value.

Some of the modifying materials that thermographers commonly use include flat-finish spray paint, PVC electrical tape, masking tape, and spray deodorants containing powder.

Prior to modifying any surface:

• Make sure that it is safe to contact the subject equipment.
• Obtain permission to modify the surface from the end user.
• Ascertain that the selected modifying material will not melt, catch fire or emit toxic fumes when heated.

Once you have determined it is safe to modify a surface, proceed as follows:

1. Place radiometer at desired location and distance from target. Aim and focus.

2. Measure and compensate for Reflected Temperature.

3. Apply a surface modifying material having a known E value on target making certain that material is in full contact with target and there are no air pockets. Modifying material should be larger than radiometer’s spot measurement size for the chosen distance from the target.

4. Enter E value of modifying material into radiometer’s E setting.

5. Measure temperature of modifying material once it has reached thermal equilibrium with target.

6. For greater accuracy, repeat measurement three times and average the results.

For more information on the above technique, refer to the Infraspection Institute Guideline for Measuring and Compensating for Reflected Temperature, Emittance and Transmittance available from Infraspection Institute.

Fire Resistant Clothing is required Personal Protective Equipment for many who work in high temperature areas or near energized electrical equipment. If your job requires the use of FRC, there are several important things of which you should be aware.

Not all garments classified as FRC are created equal. When choosing FRC you should be aware that:

• FRC is not fireproof. It is designed to protect the wearer from burns by resisting ignition during brief periods of high temperature exposure such as electrical arc flashes.
• FRC is manufactured with different materials and different weights. Be certain that the chosen material is appropriate for the task at hand.
• FRC effectiveness can be compromised by age, wear, contamination with flammable materials and the attachment of name patches or embroidery. FRC can be permanently damaged by improper cleaning or laundering.
• FRC is only effective when it is worn properly. It should always be worn as the outer-most garment. If worn over other layers clothing, the undergarments should be made of natural fiber and completely covered by the FRC.

Before wearing FRC, be certain to understand its proper application and limitations and how to use it properly. As always, remember to work safely!

Glass viewing windows and plastic safety barriers are common features found on medium and high voltage electrical enclosures and devices. Although glass and many plastics are transparent in the visible spectrum, they are opaque in the infrared spectrum.

Because infrared equipment cannot accurately see through glass or plastics, infrared inspections must be conducted with these materials out of the line of sight of the infrared test equipment. When plastic barriers are present, try the following:

• Shift your viewing angle to try to see around or behind the barrier
• Have the qualified assistant temporarily remove the barrier observing proper safety precautions
• If barrier is short and the subject device is connected to insulated conductors, image conductors and report any inexplicable temperature rise.

When safety glass view ports are encountered in switchgear enclosures, it will be necessary to have the qualified assistant open/remove the subject panels. If this cannot be done due to safety interlocks, other types of electrical testing should be performed during regularly-scheduled PM shutdowns. As always, any obstructed equipment or equipment not inspected should be noted as such in the final written report.

When working in a new facility or plant area for the first time, you may encounter safety rules that are new or different. It is always a good idea to review safety requirements with the project manager prior to project start to ensure that you are prepared.

When contacting a project representative concerning safety, be sure to ask the following:

• What general safety training and/or site specific training is required?
• Is special clothing, shoes or other Personal Protective Equipment required?
• Can infrared and related test equipment be used in the subject areas?
• Are respirators or additional safety equipment/monitors required?
• Will the work involve hazardous locations such as confined spaces, scaffolding or elevated platforms?
• What medical conditions might preclude a person from working in the subject area(s)?
• Are there site specific emergency procedures including evacuation, designated rally spots and how to report an incident?

Once the project commences, be sure to maintain good situational awareness and always stay with your qualified assistant. Becoming familiar with area safety rules in advance of a project can help to avoid cancelled projects and embarrassment while helping to maximize safety.

When performing infrared temperature measurements, reflected infrared energy can be a significant error source. This potential error source can be overcome by using the proper radiometer and test procedure.

All thermographers have experienced reflected energy when inspecting low emittance targets. For qualitative imaging, single-point reflections may be avoided by changing viewing angle.

With quantitative imaging, failing to compensate for reflected energy can account for significant measurement errors. The infrared energy received by a radiometer is the sum of emitted, reflected and transmitted energy (E+R+T=1.0). For targets with a transmittance of zero, the error sources are emittance and reflectance. Using a quality radiometer, reflected energy can be measured and compensated for by using the Reflector Method described below.

1. Set radiometer Emittance control to 1.00

2. Locate radiometer at desired distance from target to be measured

3. Aim and focus imager

4. Position diffuse reflector in front of, and parallel to, face of target

5. Measure apparent temperature of reflector surface and remove reflector

6. Enter value obtained in Step 5 into radiometer’s computer under reflectance input – commonly labelled Background, TAmbient, or Reflected Temperature.

Be sure to maintain a safe working distance from any energized or potentially dangerous targets. For more information on this subject, refer to Infraspection Institute’s Guideline for Measuring and Compensating for Reflected Temperature, Emittance & Transmittance.

Proper conduct of an infrared inspection requires line of sight access to the object(s) being inspected. A first surface mirror can often be utilized to inspect components that may be obstructed or obscured.

A first surface mirror is a special optical mirror that has a highly reflective coating adhered to the front of the mirror substrate. For infrared inspections, first surface mirrors can be temporarily utilized as reflectors to inspect areas that are inaccessible or unsafe for a thermographer to enter.

When using a first surface mirror with your infrared imager, keep the following in mind:

• Select a mirror of sufficient size for the selected imager and target
• Inspect mirror prior to use for cleanliness and condition
• Place the mirror in the optical path between the imager and object being inspected
• Position the mirror so that the reflective side of the mirror faces the imager
• Inspect object by imaging mirror surface

First surface mirrors are commercially available from a number of scientific suppliers that deal with optics and lasers. When using a first surface mirror, be certain to follow necessary safety precautions, especially when working near energized electrical components.

Whether you are considering instituting an IR inspection program or already have one in place, obtaining competent manpower can be a challenge. One potential solution is to outsource services for additional manpower and expertise.

There are many factors that will determine if a person is capable of effectively supporting your infrared program. Your success in qualifying your thermographers can be increased if you keep the following in items in mind when qualifying individual thermographers.

1. Proof of formal infrared training and certification level
2. Amount of experience with the type(s) of inspections planned
3. Experience with the selected test equipment
4. Knowledge of the system(s) being inspected
5. Documentation of requisite safety training

If you choose to outsource your thermographers through an infrared consulting firm, you may also wish to check the following.

• Number of years in business
• Type of infrared equipment to be utilized and calibration dates
• Insurance coverage
• Safety records and experience modification rating
• Professional references

Depending upon your company requirements, be sure the chosen vendor is capable of complying with security, background screening, and substance abuse policy requirements.

With the onset of seasonably cooler weather, autumn is the time to prepare your steam system for the upcoming heating season. Testing your steam traps before the season begins can help to pinpoint costly leaks before the heating season begins.

Traditionally, two different non-destructive technologies have been employed to test steam systems – contact ultrasonics and temperature measurement. Used individually, each of these techniques has limitations that can lead to false positive and/or false negative results. Combining temperature measurement with ultrasound can result in a highly accurate test method by following a few simple steps:

• Measure trap inlet to ensure that temperature is above 212º F
  • If trap inlet is below 212º F, ascertain why steam is not reaching trap
• Listen to the trap outlet with contact probe of ultrasonic unit
  • Continuous hissing or rushing sounds usually indicate a failed trap
• Ascertain that trap is cycling periodically
  • Frequent cycling may be caused by an undersized or worn trap
• Tag defective traps and document in written report
• Re-test defective traps after repair to ensure effectiveness of repair.

Always be sure to follow appropriate safety precautions especially when working with high pressure steam or when using ladders or lift equipment.

Most modern thermal imagers have the ability to record time and date along with thermal images. Taking a moment to ensure that the correct time and date are displayed on your imager before you begin your inspection can help to avoid wasted time and the collection of inaccurate data.

Having the correct time associated with your imagery is important for several reasons. With correctly dated imagery, it is possible to:

• Accurately document when the inspection was performed
• Easily store and uniquely reference image files
• Record the duration of a thermal event

It is always good practice to consciously check your imager’s clock each time you start your imager and make any necessary adjustments. Be certain to check your clock periodically during your inspection and whenever you restart your imager such as after a battery change or power interruption.

If your imager frequently displays incorrect time, it may be indicative of a defective or dead internal battery. To help avoid this problem, arrange for replacement of internal clock batteries whenever you have your imager serviced or repaired.

Taking your infrared imager into dusty or wet environments can have disastrous consequences for your imager. While it is best to wait for such conditions to subside, your can use a polyethylene sheet or trash bag to temporarily protect your imager and accomplish a qualitative inspection.

Since not all imagers and trash bags are created equal, you can follow the following steps to ensure good results.

1. Set up imager looking at thermally stable target with a high emittance. If using an imaging radiometer, note the apparent temperature of the target.

2. Select a clean, unused, polyethylene trash bag with a uniform thickness.

3. Open trash bag and place over imager. Use only a single layer of the bag plastic to cover the lens.

4. Use a rubber band to keep plastic smooth and wrinkle free over the imager lens.

5. Image target in Step 1 again and note image quality and apparent temperature.

6. Repeat above steps using different brand bags and thicknesses until you find a bag that gives minimal attenuation of image and apparent temperature.

7. After selecting the bag that works, trim to fit imager so as to prevent a tripping hazard. If your imager requires air cooling, leave the bottom of the bag open so the imager can ‘breathe’.

8. When finished imaging, remove bag from imager and discard.

While not glamorous, this procedure can allow you to successfully perform a qualitative inspection in an environment that might otherwise harm your imager.

Whether you are facing an equipment shortage or looking to evaluate the characteristics of a new imager prior to purchase, renting a thermal imager may provide a solution. As with purchasing an imager, there are several important things to consider when arranging for a rental unit.

To help ensure that you select an appropriate imager for rental, be certain to:

· Identify appropriate spectral response required for project

· Determine if temperature measurement is required

· Evaluate the system for objective specifications

· Ascertain imager compatibility with reporting software

When arranging for a rental, obtain terms and conditions from the rental agency. These should include, but not be limited to: rental period, extension of rental, shipping costs, and requirements for insurance against loss. One should also consider the rental agency’s ability to provide technical support during the rental period.

For more information on specifying an infrared imager, refer to the article, “Selecting, Specifying, and Purchasing a Thermal Imager” which may be found on this website here.

Lastly, the greatest limiting factor in any infrared inspection is the thermographer. For accurate results, infrared inspections should be performed by properly trained and certified thermographers. For more information on training, please contact Infraspection Institute.

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

For the past decade, the document, NFPA 70B Recommended Practice for Electrical Equipment Maintenance, has recommended annual infrared inspections of electrical systems. The 2002 edition of NFPA 70B contains several revisions of which thermographers should be aware.

The 1994 edition of NFPA 70B outlined many important issues surrounding infrared inspections including training, equipment, required conditions, inspection frequency, and reporting. The 1998 edition expanded on these issues and referenced temperature limit benchmarks. The 2002 edition text is nearly identical to the 1998 edition for the chapter, “Infrared Inspections”; however, there are some important changes:

• Specifications for Infrared Inspections have been moved from Chapter 18-17 to
  Chapter 20.17
• Chapter 20.17.52 is a new addition, requiring that circuit loading characteristics be included as part of report documentation

The 2002 edition also contains a completely revised Annex I recommending infrared scanning at least once per year for the following equipment:

• Outdoor Substations
• Switchgear Assemblies
• Stationary Batteries and Chargers
• Motor Control Equipment
• Low Voltage Busway
• UPS Systems

As with previous editions, NFPA continues to recommend semi-annual or quarterly infrared inspections for equipment “…where warranted by loss experience, installation of new electrical equipment, or changes in environmental, operational, or load conditions.”