So, you have a thermal imager... Now what to do?
This article outlines steps to assist in the growth of a thermographic programme into a key part of the way a company does business.
The first thing to do is gain support from management
Send management a summary of what has been learned in thermographic training and offer ideas for what can happen next. Communicate what support is desired and find out how thermographic performance results will be measured.
Practice reading thermographic images
Aim for using the camera 2-3 times each week over the first six months to gain expertise. Plan the work, track the findings, and document the results from the beginning.
Meet regularly with first level managers, line supervisors and other co-workers
Explain what thermography involves, demonstrate the camera, ask for their support and set up a mechanism for them to request thermographic surveys. Set up a trophy board of thermal image discoveries to help communicate your programme throughout the facility.
Integrate with other predictive maintenance efforts
Thermography is often part of a larger predictive maintenance (PdM) programme. Data from several technologies, such as vibration, motor circuit analysis, airborne ultrasound, and lube analysis can all be used to study the condition of a machine asset. Ideally, these technologies will work from and with the same computerised maintenance management system (CMMS), to access equipment lists and histories as well as to 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 done safely. Key ingredients include safety, conditions required, and guidance for interpreting the data.
The 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 minimise 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 specific inspection procedures, review the industry standards that currently exist, see if the company has procedures that can be used as a guide and then start with the major electrical and mechanical applications and refine them as the programme is developed.
Avoid prioritising findings based on temperature alone. Temperature measurements identify problems quite well, but they are not the best way determine the cause of a failing component. Inspection procedures should address the conditions required to locate problems, using thermography, as well as acknowledge the 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 as a guide: 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 2-3 hour inspection blocks. The lists may not be up to date, so one should expect the first inspection cycle to take more time to allow for the locating of equipment, updating of lists, dealing with access issues, and so forth. During the 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 to the plant, the first few inspection cycles may yield a large number of finds. Subsequent inspections should go more smoothly. After about three cycles, re-organise 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. This latter point is important enough that time should be devoted to researching past failures, through discussions with co-workers and by reviewing plant records. Once the equipment has gone through several cycles of inspection, it may be found that the frequencies in Table 1 are a good target.
It is also vital to inspect all new equipment both as part of the acceptance process as well as, 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 off site 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 OK until the follow-up proves it.
Conditions may not be right for an inspection when it comes due. This incomplete work must be rescheduled before the next cycle, so reserve time for makeup work. A list of equipment will develop 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 to go.
* Charge the batteries.
* Ensure that the system is within calibration by viewing a black body reference or conducting a simple 'tear duct check'. Some units like the Raytek Ti30 feature self-calibration.
* Clear the memory of previously recorded data.
* If a previously followed inspection route is to be run, 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 equipment, or a voice recorder, etc, assemble all of it and make sure it is in good working order.
Sit down with co-workers from the area where the day's work will be conducted. Discuss concerns (for safety, equipment conditions, etc) and note any unusual conditions that might impact the 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 go over the requirements with any assistants. Typically the assistant/escort will locate the exact equipment to be inspected, remove panel covers, take load readings, and watch out for the safety of the thermographer while the thermal imager is being used. He or she should also be able to fill in any necessary information about equipment conditions or peculiarities. During the preliminary meeting, it is also important to identify the exact person who should be notified if an alarm or emergency condition is encountered.
Whenever entering 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 very useful supplemental signature and a level of assurance that things are safe.
Unless conducting a first-time baseline inspection, only record thermal images when problems or 'exceptions' are located. Take time to look at the finding from several different angles and collect any other data that might be useful for analysis, including additional visual images of the component. Do not worry about actually measuring temperatures until a problem is found. 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 back 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 off. Once the inspection of an enclosure is complete, 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 the findings. Prepare them for what will be included in the report, let them know when the report will be coming, and discuss when the next inspection cycle will occur.
Download any data 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 the 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 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-energised. Many plants have reported good 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, routing 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 aluminium - 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
The software that comes with the Raytek Ti30 Thermal Imager supports simple but useful comparisons of asset condition over time. An alarm temperature can be loaded onto an image before it is uploaded into the camera. During the current inspection, both that alarm setting and the previous image can be used to determine the extent of any changes that might have occurred. The new thermal image and data document the new condition. This can all be included in a report generated back in the office. Matching thermal and visual images is very 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. Be careful in the report to use the area measurement tools (typically showing the maximum, minimum and average temperatures for the selected area), rather than the spot measurement tools whenever possible. This will ensure that the true maximum temperature is being read. 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 customised to suit the requirements. If possible, find a way to tie the report into the work order generated by the CMMS so that the 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 either repair or further monitoring or managed in some other way, such as reducing load, to minimise the risk of failure. Assets in good condition (green) are ready and available to make the plant profitable. Every machine asset may not be green, but at least it will be known where the problem areas are and it will become possible to anticipate their condition in the larger picture of plant operations. Reports organised using the green/yellow/red indicators quickly show whether overall plant asset health is improving, a powerful communication to managers.
Key indicators to track results
Analysis of data over the long term is very important, so plan on accumulating it in forms that facilitate this process. The benefit is twofold. First, trends that may not be obvious in a day-to-day analysis will be easier to see. For instance, it may be discovered 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 continuing problems are revealed, allowing the justification of 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 to get the best returns.
In addition to the measurements, also track increased machine asset availability, production, production quality, and the distribution of maintenance funds and total maintenance costs over time. Enrol the manager and the maintenance team in tracking this data. The assumption is that if inspections are conducted on time, follow-up inspections are performed, etc, the results will show up in the bigger picture.
Other opportunities
Using thermography to look at other manufacturing process applications can have great value. One thermographer found warm air from the production process blowing directly onto a heat exchanger. Interestingly, the process had shut down repeatedly due to the failure of the exchanger to provide adequate cooling. Engineers had planned to add a larger exchanger to 'solve' the problem.
Another thermographer in an automotive assembly plant happened to look at the incoming tyres and noticed how cold they were. When he showed the image to the area manager, the two quickly connected this condition to a seasonal problem they had had for years in which the tyres failed to mount properly on the rims. The solution? Bring the tyres inside long enough to warm up, a condition documented by another thermal image.
The buildings we work in may also have problems that can be solved with thermography. Facilities maintenance can use thermography for roof moisture inspections, locating building air leakage, analysing the distribution of conditioned air from HVAC, locating underground drains, pipes and lines, solving comfort related problems in the office workspace, and inspecting battery backup (UPS) for computer systems.
Of course, thermographers looking at processes are not limited to simply measuring temperatures or seeing thermal images. If the time is taken to correlate them, moisture, thickness, coatings, material type and parts presence will typically all have their own characteristic thermal signature as well. Manufacturing processes are not always simple to look at but doing so can often yield a perspective 'Thinking Thermally' that may be the key to finding solutions to costly problems.
This finding, an internal fault in a pole-mounted transformer feeding a critical load, was considered serious enough that it could not wait for a scheduled shutdown. Protocols should be established before the inspection to handle situations like these effectively.
For more information contact Vince Pinnock, R&C Instrumentation, 032 946 2805, www.randci.co.za
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