Pumps & Systems, November 2008
A successful infrared program involves planning and action. This article outlines steps that will help you implement a thermography program.
Getting Started
Gain Support from Management
Send management a summary of what you learned in thermography training and your ideas for the next steps. Communicate what you would like in the way of support and find out how thermography performance results will be measured.
Practice Reading Thermographic Images
Aim for using the camera two to three times each week throughout the next six months to gain expertise. Plan your work, track your findings and document results from the beginning.
Meet Regularly with First Level Managers, Line Supervisors and Other Coworkers
Explain what thermography involves, demonstrate the camera, ask for support and establish a mechanism for thermography survey requests. Set up a trophy board of thermal image discoveries to help communicate your program throughout the facility.
Integrate with Other Predictive Maintenance Efforts
Thermography is often part of a larger predictive maintenance (PdM) program. Data from several technologies, such as vibration, motor circuit analysis, airborne ultrasound and lube analysis, can be used to study the condition of a machine asset. Ideally, these technologies will work from and with the same computerized maintenance management system (CMMS) to access equipment lists and histories as well as store reports and manage work orders.
Establish Written Inspection Procedures
Written inspection procedures drive the quality of the data collected and ensure the inspection is completed safely. Key ingredients include safety, conditions required and guidance for interpreting the data.
National Fire Protection Association (NFPA) 70E requires that all personnel be educated about the risks they face when working near electrical equipment. Personal protective equipment (PPE) must also be made available to minimize the risk if an accident should occur. For thermographers, PPE generally includes flash-resistant clothing and a face shield.
As a starting point for creating your specific inspection procedures, review the industry standards that currently exist. See if your company has procedures that can be used as a guide and then start with the major electrical and mechanical applications and refine as you develop the program.
Avoid prioritizing findings based on temperature alone. Temperature measurements identify problems extremely well and may help characterize problems, but they are not the best way to determine the cause of a failing component. Your inspection procedures should address the conditions required to locate problems using thermography and other technologies needed to troubleshoot further.
Creating Inspection Routes
Begin by using existing lists of equipment from a CMMS or other inventory. Eliminate items that are not well suited for infrared measurement and focus on equipment that creates production bottlenecks. If possible, look at history to guide you; where have failures occurred in the past?
Use a database or spreadsheet to group the remaining equipment together, either by area or function, into roughly 2- to 3-hour inspection blocks.
The lists may not be up to date, so you can expect the first inspection cycle to take more time as you locate equipment, update lists, deal with access issues, etc. During your first pass, also consider taking digital photos of each piece of equipment and storing the images in the equipment database for later reference, as needed.
If thermography is new in your plant, the first few inspection cycles may yield a large number of finds. Subsequent inspections should go more smoothly. After about three cycles, reorganize the routes so they are more efficient, and add new routes and equipment into the inspection cycle as necessary. The optimum frequency of inspection will be determined by the needs of the equipment assets. As they age, are heavily loaded or are poorly maintained, inspections may become more frequent.
Frequency of inspection is based on a number of factors. The key drivers are safety, the criticality of the equipment, the expense of a failure and the frequency with which problems impact production and/or maintenance. The last point is important enough that you should devote time to researching past failures, discussing with coworkers and reviewing plant records. Once the equipment has gone through several cycles of inspection, you may find the frequencies in Table 1 are a good target.
Equipment Type
Frequency of Inspection
High voltage substations
1-3 years
Transformers
Annually
440V Motor Control Centers (Air conditioned)
6-12 months
Non-air conditioned or older
4-6 months
Electrical distribution equipment
4-6 months
Large motors*
Annually
Smaller motors
4-6 months
* Assumes vibration analysis, MCA and lube analysis are also being used
It is also vital to inspect all new equipment as part of the acceptance process and, for larger equipment, to establish a baseline. If equipment is damaged on arrival, inspect it as soon as possible to determine its actual condition. Some plants send their thermographers offsite to inspect new equipment before it is delivered, often finding deficiencies and problems before the equipment is accepted. When repairs or modifications are made to equipment, the CMMS must alert the thermographer to conduct a follow-up inspection; all too often a repair is not adequately made, for a variety of reasons, so do not assume everything is okay until the follow-up proves it.
Conditions may not be right for an inspection when it is scheduled. This incomplete work must be rescheduled before the next cycle, so reserve time for makeup work. You will also develop a list of equipment that needs increased monitoring until it can be repaired; many thermographers add these pieces into a weekly route until the condition changes.
Conducting Inspections
Working from a pre-inspection checklist is a good idea:
- Make sure the thermal imager is ready.
- Charge the batteries.
- Ensure that the system is within calibration by viewing a black body reference or conducting a simple "tear duct check."
- Clear the memory of previously recorded data.
- If you will be following an inspection route that has been inspected previously, upload past results to the camera so they can be compared to new findings.
- If additional equipment is required, such as a digital clamp meter for load reading, a voice recorder, etc., assemble all of it and make sure it is in good working order.
Sit down with coworkers from the area where you will be conducting your day's work. Discuss concerns (for safety, equipment conditions, etc.) and note any unusual conditions that might impact your work. Ask about any problems they have noted. Because routine inspections should generally be conducted by more than one person, this is also a good time to discuss your needs with your escort. The escort will typically locate the exact equipment to be inspected, remove panel covers, take load readings and watch out for the safety of the thermographer while the imager is being used. He or she should also be able to fill in any necessary information about equipment conditions or peculiarities. During the pre-job meeting, it is also important to identify the exact person who should be notified if an alarm or emergency condition is encountered.
Whenever you enter an inspection area, take a moment to get oriented, determine an emergency exit strategy and note any potential hazards. Many thermographers begin an electrical inspection by looking first at the panel covers while they are still closed; if any appear abnormally warm, it may be appropriate to take further safety precautions before accessing the equipment inside. Airborne ultrasound detection equipment can provide a useful supplemental signature and a level of assurance that things are safe.
Unless you are conducting a first time baseline inspection, only record thermal images when problems or "exceptions" are located. Take time to look at the findings from several different angles and collect any other data that might be useful for your analysis, including additional visual images of the component. Do not worry about actually measuring temperatures until after you have found a problem. At that point, if it is appropriate, the correct emissivity and reflected temperature correction (RTC) can be used. Additional analysis is often easier to do in the office at the computer.
For electrical enclosures, such as an MCC panel, open only as many panels as is safe. If enclosure doors are left open for too long, any problem hot spots may cool. Once you have finished inspecting an enclosure, the escort should close the cover to ensure the safety of anyone in the area. If necessary, post signs or barricades around an area during the inspection.
When the inspection is complete, meet briefly with the area manager(s) and review your findings. Prepare them for what you will say in your report, let them know when the report will be coming and discuss when your next inspection cycle will occur.
Download any data you have collected after each route as soon as possible to reduce the risk of accidental erasure. Delete any unnecessary images and process the rest individually, fine-tuning temperature measurements and making any adjustments to temperature level and span settings. Enter any supplemental data into the report page, along with the visual image of the equipment inspected.
When the inspection report is complete, add the area manager and/or operator(s) to your distribution list. As a final task, update the equipment list with any changes, additions or deletions.
Modifications to Improve Inspection Quality
The following suggestions for modifying plant equipment are designed to make your inspections easier, safer and more effective:
- High-emissivity "targets" installed on such components as bus bars, tubular bus and any large metal electrical connectors can dramatically improve the reliability of radiometric temperature measurements. While there are no standards for how to create such targets, they must be installed while the equipment is de-energized. Many plants have reported success using spray paint (flat and, if outside, white)-especially brands designed to be used on electronic components, electrical tape and paper stickers. Targets only need be installed near connection points.
- Infrared transparent "windows" (either a crystalline material or a special plastic) installed in electrical panel covers, especially high voltage, make it possible to inspect the components without opening the enclosure. Only install these in locations that allow for complete inspection.
- The clear plastic, "touch-safe" covers that are increasingly prevalent inside electrical control cabinets are not transparent to infrared! It may be possible to modify these with hinges or, if necessary, route small holes in them over the connectors and fuse clips.
- Modify equipment guards and covers on conveyance systems and motor couplings so that bearings and couplings can be inspected. Consider installing a small hinged door or using metal mesh instead of solid metal, as long as it does not compromise safety.
- Thermal mirrors-thick sheets of plate aluminum-can make it easier to see a thermal signature. To view the end bearings of large vertical motors, mount a thermal mirror above and angled down. To view up under a process or machine, place a thermal mirror on the floor.
Reporting Results
Matching thermal and visual images is useful, and a second thermal image, either a comparison over time or a follow-up image, can also be included.
Clearly identify the equipment inspected as well as the conditions found. Use the area measurement tool showing maximum, minimum and average temperatures for the area, rather than the spot measurement tool whenever possible. This will ensure that the true maximum temperature is being identified. It is also important to report the conditions found during the inspection with regard to equipment loading and environmental variables. Note both the emissivity and the reflected background temperature corrections used.
The actual report format can vary widely and can be customized to your needs. If possible, find a way to tie your report into the work order generated by the CMMS so that your findings can be tracked through their useful life.
Once the infrared data is correlated with data from other technologies, the actual operating condition of all assets will be known and can be reported in an integrated form. Those assets that are in an alarm stage (red) or an unknown stage (yellow) can then be scheduled for repair or further monitoring or managed in another way, such as reducing load to minimize the risk of failure.
Assets in good condition (green) are ready and available to make your plant profitable. Every machine asset may not be green, but at least you will know where the problem areas are and can anticipate their condition in the larger picture of plant operations. Reports organized using the green/yellow/red indicators quickly show whether overall plant asset health is improving, which powerfully communicates to managers.
Key Indicators to Track Your Results
Analysis of data over the long term is important, so plan on accumulating it in forms that facilitate this process. The benefit is twofold. First, you will see trends that may not be obvious in a day-to-day analysis. For instance, you may discover that the motor shop is doing a poor job, or that a certain brand of fused disconnect consistently has problems.
The second benefit is that you will see what is working (or not!) about your program. You will see where problems are continuing to occur, enabling you to justify dedicating resources in those areas or decreasing the frequency of inspection because few problems are being found. It can also help target maintenance investments and allocation of maintenance funds for the best returns.
In addition to your measurements, also track increased machine asset availability, production, production quality and the distribution of maintenance dollars and total maintenance costs over time. Enroll your manager and the maintenance team in tracking this data. The assumption is that if you conduct your inspections on time, perform follow-up inspections, etc., the results will show up in the bigger picture.
Conclusion
In summary:
- Communicate thermography plans with managers and operators
- Integrate thermography into existing predictive maintenance programs
- Review safety standards and procedures
- Create an equipment list, schedule and inspection routes
- Capture baseline images of all critical equipment during first survey
- Download images after each survey and convert data for tracking
- Create a report template and distribute results after each survey
- Set up alarms for image comparison and key indicator tracking over time
- Modify inspection conditions, lists and routes over time as necessary
By following these steps, you will develop a successful thermography program that will reduce maintenance costs for your company while also improving productivity.