Temperature is frequently used to gauge the condition of motors and power-transmission equipment. The following information applies to flexible drive belts and the temperature limits for them.
Drive belts are an integral component on many types of machines. Despite the critical role they play in machine operation, V-type drive belts tend to be out of sight and out of mind until they fail. In most installations, belt temperature largely influences the life of installed V belts.
As a rule of thumb, properly applied and maintained belts should not exceed 140 F (60 C), assuming an ambient temperature of less than 110 F (43 C). Belt life can be greatly reduced by higher operating temperatures. In fact, for every 18 F-deg. (10 C-deg.) increase in belt temperature, belt life is cut in half. Keeping this in mind, we can see that the life of a drive belt operating at 176 F would be reduced by 75%.
Thermogram shows overheating V-belts. Note castoff in the control photo. Images courtesy of Skip Handlin.
Many factors contribute to high belt-operating temperature, including, but not limited to, ambient air temperature, machine design, installation, alignment, and belt tension. Overheating belts that afford line-of-sight access can be readily detected and documented with an infrared imager.
Issues associated with overheating in drive belts may not be limited to the belts themselves, however. With regard to over-tensioned drive belts, excessive force applied to belts is often transferred to bearings in the driven system. In these situations, it’s not uncommon to see bearings overheat due to the excess force created by the over-tensioned belt(s).
Thermogram shows the effects of an improperly tensioned V-belt. In this example, over-tension causes both the belt and adjacent pillow block bearing to run hot.
It should be noted that the operating temperature of overheating drive belts is not necessarily linear. A worn belt that has reached critical temperature will begin to wear at an accelerated rate, which, in turn, will cause the belt to run hotter and wear even more quickly. This vicious cycle will continue until the belt either breaks or fails to perform its intended task.
Once detected, overheating belts should be investigated for cause and proper corrective measures undertaken as soon as possible. Doing so can help prevent unscheduled downtime and may prolong belt life.
Thermal imaging offers several distinct advantages over other types of inspections for belted systems. Thermal imaging is non-contact and nondestructive. Imaging is performed remotely and requires no shutdown of inspected systems. Because infrared imagers produce real-time data, results are instantaneous and allow rapid inspection. MT
Jim Seffrin, a practicing thermographer with 30+ years of experience in the field, was appointed to the position of Director of Infraspection Institute, Burlington, NJ, in 2000. This article is based on one of his “Tip of the Week” posts on IRINFO.org. For more information on infrared applications, as well details on various upcoming training and certification opportunities, email email@example.com or visit infraspection.com.
Infrared cameras, also called thermal imagers, can be important tools for troubleshooting motor problems, as well as for monitoring motor conditions for preventive maintenance. Infrared images reveal a motor’s heat signature, which can tell you a lot about its condition. The condition of motors, in turn, can play an important role in keeping plants up and running and their operating costs down.
According to experts at Fluke Corp., Everett, WA, here are some tips for scanning motors and drives with thermal imagers:
Build motor heat-signature profiles.
Capture good quality infrared images when the motors are running under normal operating conditions. That gives you baseline measurements of component temperatures. Make infrared images of all of the critical components, including motor, shaft coupling, motor and shaft bearings, and the gearbox. Note that when working with low electrical loads, the indications of a problem can be subtle. As a load increases, the temperature will increase. If a problem exists, expect greater temperature differences at higher loads.
Note nameplate information and hot spots.
A motor’s normal operating temperature should be listed on the nameplate. An infrared camera cannot see the inside of the motor, but the exterior surface temperature is an indicator of the internal temperature. If a motor is overheating, the windings will rapidly deteriorate. Every 50-deg. F increase in a motor’s windings, above the designed operating temperature, cuts the winding life by 50%, even if the overheating is only temporary. If a temperature reading in the middle of a motor housing comes up abnormally high, an IR image of the motor can tell you where the high temperature is coming from, i.e., windings, bearings, or coupling. If a coupling is running warm it is an indicator of misalignment.
Know the three primary causes of abnormal thermal patterns.
- High-resistance contact surface, either a connection or a switch contact, often appears warmest at the spot of high resistance.
- Load imbalances can appear equally warm throughout the phase or part of the circuit that is undersized/overloaded. Harmonic imbalances create a similar pattern. If the entire conductor is warm, it could be undersized or overloaded. Check the rating and the actual load to determine the cause.
- Failed components typically look cooler than those that are functioning normally. The most common example is probably a blown fuse. In a motor circuit, this can result in a single-phase condition and the possibility of costly damage to the motor.
Create regular inspection routes and compare images.
It is a best practice to create a regular inspection regimen that includes making thermal images of all critical motor/drive combinations. Ideally, these images are made under identical operating conditions to have apples-to-apples comparisons. Comparing current state images with baseline images can help you determine whether a hotspot is unusual and also help you verify if any repairs undertaken were successful. A thermal imager can easily transfer images into software for cataloguing. Sharing can be invaluable in this effort. MT
For more information on thermal-imaging best practices, visit fluke.com.
By James Seffrin, Director, Infraspection Institute
When working in a new facility or plant area for the first time, infrared technicians may encounter safety rules that are new or different. Thus, it’s important for thermographers to review safety requirements with project managers prior to beginning any new work.
When contacting a project representative concerning safety, ask these questions:
- 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 other types of 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 maximize safety.” MT
Electrical-Inspection Safety: It Takes Two
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’s 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 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.
Remember: Having a second CPR-trained person along will not only satisfy OSHA requirements, it may save your life.
Jim Seffrin, a practicing thermographer with 30+ years of experience in the field, was appointed to the position of director of Infraspection Institute, Burlington, NJ, in 2000. This article is based on two of his “Tip of the Week” posts on IRINFO.org. For more information on safety and other infrared applications, as well as various upcoming training and certification opportunities, email firstname.lastname@example.org or visit infraspection.com.
By R. James Seffrin, Director, Infraspection Institute
Successful thermography begins long before actual field work begins. The final results for any project depend upon understanding the task(s) to be performed, selection of equipment, operator skills, inspection techniques and documentation of findings. Failure to understand how these factors contribute to the final conclusions can lead to serious errors. To ensure optimum results, a thermographer must understand the nature and reason for the inspection, all equipment and operator limitations, site conditions and how to document findings.
The use of infrared thermography for predicitve maintenance (PdM) and condition-based monitoring (CBM) is now widely recognized. The benefits of infrared thermography coupled with lower equipment costs have led to a greater public awareness of common applications. Research continues to broaden the applications of thermography. Advances in equipment now allow thermographers to routinely perform tasks that could only be dreamed of as little as 10 years ago.
Common applications of infrared thermography now include electrical and mechanical systems, building envelopes, insulated roofs, petrochemical processes, transportation and medicine. In the manufacturing environment, the ability to distinguish high temperatures in rotating equipment, especially motors, allows maintenance organizations to apply highly effective predictive and preventive strategies. This is because a thermal image makes immediately clear what part of the motor is overheating, and to what extent.
According to infrared camera maker Fluke Corp., standard practice for thermographic imaging follows three basic methods:
- Regular comparison of the operating temperatures of like equipment, performing similar functions
- Regular comparison of the operating temperature of a single unit to manufacturer’s standards
- Regular comparison of the operating temperature of a single unit to previous images of the same unit
Since the thermographer guides the infrared inspection process, his/her knowledge is of the utmost importance. Thermal imaging can be used to identify several conditions such as inadequate airflow, unbalanced voltage, impending bearing failure and insulation degradation in a motor’s rotor or stator. It can also identify heat produced by shaft misalignment.
Regardless of the application, however, the final results of a thermographic inspection depend upon understanding the task to be performed, selection of equipment, operator skills, inspection techniques and documentation of findings. Before embarking on an inspection, a thermographer needs to consider and understand how these factors will influence final results. The following steps outline the basic elements a thermographer needs to consider for a successful inspection in any environment.
Perhaps the most important—and often most overlooked—part of thermography is the need to define the project. Before any successful task can begin, the thermographer must determine exactly what is to be done and what is expected of the final results. In the case of routine inspections of industrial equipment, this will typically be understood. Infrared can and should be included in normal maintenance “rounds” to establish benchmark results for ongoing comparison.
In non-routine situations, however, specific details are needed to ensure a useful inspection. For example, a thermographer may be asked to “conduct an infrared scan to locate wet areas” on a facility’s roof, a request that does not adequately define the task. It is unclear when the work is to be performed, what type of imager is be used and what type of documentation may be required. But regardless of inspection type, it is always desirable for the thermographer to fully comprehend all aspects of what is expected. If the inspection requires skills beyond thermography, the thermographer, if qualified, may elect to perform these tasks or work with others who are qualified. Once the exact nature of the task has been determined, a scope of work can be developed.
The operator may be the greatest limiting factor in thermography. Although thermal imagers have their limitations, thermographers can overcome this by selecting the proper equipment (discussed later). Since the thermographer is the most important factor in thermography, knowledge is of the utmost importance. Unless otherwise specified, it is usually not enough for a thermographer to understand only how to operate a thermal imager to produce thermograms. At a minimum, the thermographer should have completed a Level I thermography training course. Thermographers who perform inspections involving temperature measurement should be trained to at least Level II.
The professional thermographer needs a thorough understanding of infrared theory and heat-transfer principles and how site conditions and weather can influence results. At a minimum, a thermographer must also have a basic understanding of the equipment or systems to be inspected. When a thermographer is unfamiliar with the items to be inspected, it is his/her responsibility to gain the knowledge necessary to properly conduct the infrared inspection. To this end, a thermographer must always be an expert in his/her field and be able to honestly recognize personal limitations. Anything less compromises the final results of an inspection before it begins.
The second greatest limiting factor in thermography may be the thermal imaging equipment itself. Even the best thermographer cannot compensate for equipment that cannot produce the desired information. Fortunately, today’s wide selection of equipment provides many choices for accomplishing the task at a wide range of price points. Modern thermal imagers offer features that not only make thermal imaging easier but provide more capabilities. Unfortunately, the wider selection of equipment tends to make equipment selection more difficult. And while prices on good-quality IR equipment have been dropping for some time, when it comes to imager performance, cost should be considered last.
While most maintenance organizations are confined to working with the infrared equipment on hand, situations can arise where the thermographer can select from one or more pieces of different equipment to do an inspection. Important criteria for such selection include the spectral response of the imager, color options, visual and measurement fields of view, radiometric capabilities, operating limitations and image recording. The use of accessories such as filters, heat shields and special lenses might also be required. Other important considerations include operating temperature, imager controls, display screen and whether imager is intrinsically safe.
A thermographer must always be aware of the capabilities and limitations of his/her equipment. Equipment should be maintained in good working order and calibrated in accordance with the manufacturer’s recommendations. A thermographer must also be able to honestly recognize limitations of his/her hardware.
Prior to conducting an infrared inspection, all pertinent site conditions must be considered. Limitations regarding the use of photographic equipment might preclude the use of certain equipment. Other site conditions which need to be addressed include the accessibility of the equipment to be inspected, radiation levels, airborne particles, sterile requirements and the presence of hazardous or explosive areas.
It is the responsibility of the thermographer to speak with site safety personnel prior to a project to identify pertinent site conditions and determine how these conditions will affect the work to be performed. When working near energized electrical equipment, for example, precautions must be taken to protect personnel from electric shock and arc flash hazards. Weather and environmental conditions also have a significant effect on thermal imaging and must be considered when conducting any outdoor inspection. At a minimum, this should include the following factors:
- Intense summer sunlight can make imaging work difficult.
- High winds can obscure temperature exceptions.
- Precipitation usually cancels outdoor work altogether.
Even normal weather conditions play a role in outdoor thermography. In the case of an infrared roof inspection, for example, the amount of daytime solar loading and wind will have a direct effect on the post-sunset thermal patterns regardless of weather conditions at night. Often, daytime weather conditions can influence the subject structure or systems for several hours after sunset.
To ensure optimum results, a thermographer needs to understand and consider how weather conditions will affect final results. When weather is less than optimum, a work postponement may be the wisest decision.
The final documentation of an infrared inspection is the formal record of a project. Plant requirements may vary in this regard, but proper documentation will detail how and when an inspection was performed; who performed the work; weather conditions; any special procedures followed; the results of the work; and conclusions or recommendations. The report should also include all relevant graphics, photographs and thermograms.
With the advent of more sophisticated imaging equipment and advances in computers, thermograms are no longer limited to monochrome prints. Color thermograms, video recordings and digital images are now more common. Laptop computers and powerful software allow the thermographer to prepare reports while in the field. Above all, the report should be clear and sufficiently document inspection techniques and site conditions in order that future inspections may be carried out under similar circumstances.
Keep in mind that successful thermography begins long before the actual field work begins. The final results for any inspection depend upon understanding the task(s) to be performed, selection of equipment, operator skills, inspection techniques and documentation of findings. Failure to understand how these factors contribute to the final conclusions can lead to serious errors. To ensure optimum results, a thermographer needs to understand the nature and reason for the inspection, all equipment and operator limitations, site conditions and how to properly document his/her findings. MT
R. James Seffrin is a Level III Certified Infrared Thermographer and Director of Infraspection Institute located in Burlington, NJ. He has over 30 years experience in performing infrared inspections for a wide variety of commercial, industrial and residential applications. Jim is also a co-author of several industry standards and qualified as an expert witness on the subject of thermography.
IR Imaging Gives Fast Results on Gearbox Health
The ability to determine lubrication health is another key IR capability, and should be included in any PdM program. The lifeblood of any gearbox is the oil that lubricates its gears. If oil loses its ability to lubricate—or the level of oil gets too low—the gearbox will overheat and eventually fail.
Traditional preventive maintenance for gearboxes has consisted of regular oil-level checks and replenishments as needed. Some maintenance departments add a predictive element to gearbox maintenance in the form of oil sampling and analysis. Oil analysis, usually performed by an outside laboratory, reveals if the oil in a gearbox has lost its ability to lubricate. It will also detect any metal particles in the oil, a sign of gear wear that foreshadows possible failure.
While effective, oil sampling is relatively time-consuming, and can be costly. It can also require equipment shutdown. Moreover, gearboxes often are inaccessible or in unsafe locations, which can make oil-level checking and oil sampling difficult. For these reasons, thermal imaging is a good alternative PdM approach. Since gearboxes generally overheat before they fail, an infrared (IR) camera can detect when a unit is running hotter than normal and/or hotter than similar gearboxes performing similar work in similar environments.
Because thermography is a non-contact, non-destructive technology, even inaccessible gearboxes in dangerous locations can be scanned while running. The IR camara can be used to capture all thermal images as well as visible-light digital images of all units that are running hotter than normal. These processes can also reveal leaking seals where hot oil is running down the sides of gearbox cases.
Be aware that any excessive heat generated in mechanical gearboxes is the result of friction, and that inadequate lubrication is not always the source. The cause could also be faulty bearings, misalignment, imbalance, misuse or just normal wear. Still, thermography is a good first step toward a complete analysis of the condition of any gearbox.
Source: Fluke Corporation
The Trained Eye Best Sees Infrared’s Benefits
Aside from test equipment, training is the most important investment a company will make in an infrared inspection program. While advances in technology have provided a wide range of user-friendly infrared equipment, infrared thermography is not a “point and shoot” technology. Structured training will enable thermographers to better understand what infrared cameras can do, the common error sources that can influence observed thermal data, and the many ways to interpret infrared images. Infrared’s various benefits in electrical and mechanical systems are two examples of the potential value and scope of an infrared inspection conducted by a trained thermographer.
As electrical current flows through a conductor, heat is generated. Many electrical defects are accompanied by a rise in temperature for up to several weeks prior to failure. Some defects may be represented as cool components.
Infrared imaging can detect:
- Loose/deteriorated connections
- Imbalanced loads
- Open circuits
- Inductive heating
- Defective equipment
As mechanical devices operate, heat is generated. Forces such as friction, misalignment and improper belt tension cause excessive heating.
- Infrared imaging can detect:
- Misalignment of coupled equipment
- Over/under lubrication of bearings
- Over/under tension of belted systems
- Excessive friction
- Defective equipment
Source: Infraspection Institute
Fluke Corporation has expanded the Fluke Connect system with its new Ti90 and Ti95 Infrared Cameras featuring wireless connectivity. According to the company, the Ti90 and Ti95 deliver best-in-class image quality with up to 84% better spatial resolution (of handheld industrial infrared cameras priced $1000- $2000), thus allowing technicians to conduct infrared inspections from a safer distance without compromising accuracy. Their 3.5-inch color LCD screens are up to 32% larger than competitive models and offer adjustable brightness for easy viewing in most conditions.
These new cameras come with an extensive SD memory system, including a removable 8 Gb SD memory card or 8 Gb wireless SD Card. This feature allows technicians who share cameras to simply swap SD cards at the end of their shifts instead of needing to download images onto their PC before turning the camera over to the next technician.
AutoBlend and Picture-in-Picture modes are available in the included SmartView reporting software that lets technicians easily perform analyses and image adjustments/enhancements.
About Fluke Connect
The Fluke Connect system allows maintenance technicians to wirelessly transmit measurement data from their test tools to their smart phones for secure storage on the cloud and universal team access from the field. More than 20 Fluke tools connect wirelessly with the app, including digital multimeters, infrared cameras, insulation testers, process meters and specific voltage, current and temperature models.
Fluke Connect ShareLive video call allows technicians to collaborate with others, letting them see the same images and measurements, and get approvals for repairs without leaving the field.
The Fluke Connect app can be downloaded for free from the Apple App Store and the Google Play Store.