By: Colin Plastow
How to create a successful infrared thermography maintenance program.
In the manufacturing environment, managing maintenance costs while improving productivity is an ongoing challenge, with profitability lying in the balance. One way maintenance managers can eliminate downtime due to equipment malfunction is to implement a predictive maintenance program.
One of the key performance parameters in predictive maintenance is heat, which can be an early symptom of damage or malfunction. Thermal imagers are therefore the first line of defence in measuring and comparing heat signatures for each piece of equipment on the manufacturing floor. While they used to be expensive, difficult, and primarily used by large industrial facilities, today’s devices are much more compact, affordable and easy-to-use.
Building an infrared thermography maintenance program can help managers track equipment operating conditions over time and quickly identify unusual heat readings for further inspection. It also helps to reduce reactive maintenance fees and equipment repair costs, extend the lifespan of machine assets and maximize overall productivity though reduced downtime.
There are several key steps involved in a successful infrared thermography program. They are:
• Creating inspection routes
• Conducting inspections
• Making modifications to plant equipment to improve inspection quality
• Reporting results
• Analyzing data over the long term
• Applying other manufacturing process applications where thermography can be play an important role.
Creating inspection routes
Begin by using existing lists of equipment and eliminate items that aren’t well suited for infrared measurement. Focus on equipment that creates production bottlenecks. If possible, look at history to guide you to find out where failures have occurred in the past. A database or spreadsheet should be used to group the remaining equipment together, either by area or function, into roughl two- to three-hour inspection blocks.
Bear in mind that the first inspection cycle can take more time than will be needed on subsequent inspections as you locate equipment, update lists and deal with access issues. 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. Some thermal imagers have a built-in visible light camera to make this even easier.
If thermography is new to the plant, the first few inspection cycles may yield a large number of finds. Subsequent inspections, however, should go more smoothly. After about three cycles, you can re-organize the routes so they are more efficient and add new routes and equipment into the inspection cycle as necessary.
The optimum inspection frequency will be determined by the needs of the equipment assets. As they age, are heavily loaded, or are poorly maintained, it may be necessary to perform more frequent inspections.
Conducting inspections
When conducting inspections, there are several key considerations:
• Work from a pre-inspection checklist • Make sure the thermal imager is ready for use (charge the batteries)
• Ensure that the system is within calibration by viewing a black body reference or conducting a simple ‘tear duct check’. Infrared thermography measures surface temperatures and the tear duct is the external part of the body that’s closest to internal temperature.
• Clear the memory of previously recorded data
• If you will be following a previously inspected route, some cameras will allow you to upload those past results so they can be compared to new findings
• Assemble any additional equipment that is required, such as a digital clamp meter for load reading, or a voice recorder if not built into the camera, and make sure it’s in good working order.
At the end of the inspection, download any data collected after each route as soon as possible to reduce the risk of accidental erasure. Also be sure to delete any unnecessary images and then process the rest individually, fine-tuning temperature measurements and making any adjustments to temperature level and span settings. Any supplemental data should be entered into the report page, along with the visual image of the equipment inspected.
Making modifications to plant equipment to improve inspection quality
The following suggestions for modifying plant equipment are designed to make thermal imaging inspections easier, safer, and more effective.
• High-emissivity ‘targets’ should be installed on such components as bus bars, tubular bus and any large metal electrical connectors to improve the reliability of radiometric temperature measurements.
• The clear plastic, ‘touch-safe’ covers that are increasingly prevalent inside electrical control cabinets are not transparent to infrared thermography. While it may be possible to modify these with hinges, 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.
• Use thermal mirrors such as a sheet of aluminium, which can make it easier to see a thermal signature in areas that can’t be viewed directly.
Reporting results
Some thermal imagers come with software that supports simple but useful comparisons of asset conditions 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.
Clearly identify the equipment inspected as well as the conditions found. Whenever possible, use the area measurement tool showing the maximum, minimum and average temperatures for the area, rather than the spot measurement tool. 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.
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 minimize the risk of failure. Assets in good condition (green) are ready and available to make your plant profitable. While every machine asset may not be green, at least you’ll know where the problem areas are and can anticipate their condition in the larger picture of plant operations.
Analyzing data over the long term
It is important to accumulate data in forms that allow for long-term analysis. This provides several benefits, such as:
• Visibility into trends that may not be obvious in a day-to-day analysis
• Visibility into problems that are continuing to occur, enabling you to justify dedicating resources in those areas or decreasing the frequency of inspection where applicable
• The ability to target maintenance investments and allocation of mainte-nance funds to get the best returns.
In addition to infrared thermography measurements, increased machine asset availability, production, quality, and the distribution of maintenance dollars and total maintenance costs over time should be tracked.
Applying other manufacturing process applications
Using thermography to look at other manufacturing process applications can have great value. Following are two unique applications:
• One thermographer found warm air from the production process blowing directly onto a heat exchanger. Interestingly, production 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, which would have been an unnecessary and costly investment.
• Another thermographer in an automotive assembly plant looked at thermal images of incoming tires that indicated they were cold. When the technician showed the image to the area manager, the two quickly connected this condition to a seasonal problem they’d had for years in which the tires failed to mount properly on the rims. The solution? Bring the tires inside long enough to warm up, a condition documented by another thermal image.
Facilities maintenance can also use thermography for roof moisture inspections; locating building air leakage; analyzing the distribution of conditioned air from HVAC; locating underground drains, pipes and lines; solving comfortrelated problems in the office workspace; and inspecting battery backups (UPS) for computers systems.
Of course, thermography can also be used to look at processes beyond simply measuring temperatures or seeing thermal images. Moisture, thickness, coatings, material type and parts presence will typically all have their own characteristic thermal signature, and thermography can be used to monitor those kinds of conditions as well.
Today’s thermal imagers are much more affordable and easier to use than previous models and are becoming more broadly applied in manufacturing, utilities and resource industries. By following some simple steps, facility managers can develop a successful infrared thermography maintenance program that will reduce maintenance costs while improving productivity.
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