The challenge with any predictive maintenance (PdM) technology (thermal imaging, vibration, ultrasound, motor circuit testing, power quality, etc) is that the initial investment is substantial; typically measured in thousands or tens of thousands of dollars.
Without the proper analysis, companies and/or maintenance organisations:
* May decide not to implement a PdM programme because they are unable to identify all of the savings, causing them to miss out on operational efficiency improvements.
* May invest in a suboptimal solution that does not best meet their needs.,
* May spend significantly more money to establish the programme than is necessary.
*And/or may not achieve a return on investment.
Companies need to consider not only the initial equipment costs for the test tools and accessories, but also the software costs, training costs, typical service and calibration costs and overall labour costs associated with performing periodic inspections of critical equipment.
It is very important for companies and maintenance organisations to thoroughly understand their needs. In the case of thermography, companies can spend as little as a few thousand dollars or as much as $1000000 to establish an infrared predictive maintenance programme. Clearly not every company needs the million dollar solution, but is the $2500 solution really sufficient? Finding the proper balance is the goal.
Analysing the investment
Assessing a company's PdM needs starts with understanding the costs and most common sources of downtime. PdM programmes are designed to keep equipment up and running and allow companies to schedule the necessary downtime during periods of production inactivity (off shifts, weekends, periods of slower demand, etc.).
Step one is to identify the most critical equipment in the plant. This can be done through a simple process walk, starting at the beginning (raw material end) of the process and proceeding to the end (finished goods shipment) of the process. Maintenance records and equipment failure data can also help identify those pieces of equipment that are most prone to failure.
Step two is to evaluate what inspection technologies and techniques are available for the critical equipment and the most common failure modes experienced on that equipment. If electrical connections are the most common problem, thermography would be the ideal technology to implement. More importantly, an affordable thermal imager would most likely answer the needs as well or better than the most expensive imagers on the market.
It is also important to have a sense of priority in the list of possible applications. The applications for thermography are endless, since anything which has a thermal signature can be inspected with a thermal imager. While it would be nice to purchase a thermal imaging solution that addresses every possible inspection need, it may not make sense to spend an additional $50000 in order to be able to perform inspections that will only occur every three years or where the probability of finding a problem is very small (or just not that important). Also remember, that for a relatively small investment, infrequent or specialised inspections can still be performed by outside consultants who own the more expensive, more versatile and more complex equipment.
Finally, think about possible applications outside of maintenance. Manufacturing, facilities maintenance and research engineers also have a need for measuring temperatures accurately. The advantage of sharing this technology across an organisation is that it becomes easier to justify the initial investment, it speeds payback time and lessens the budget impact on any single department.
Thermal imagers come in all shapes and sizes, with various features and benefits and with a very wide range of price tags. Some of the key performance specifications for a thermal imager are listed below: Array size and type (example: 160x120 uncooled focal plane array). Thermal sensitivity of the array (example: NETD = 200 mK or 0.2°C). Optics field of view options (example: 17° x 12.8° fixed). Optical resolutions or distance to spot ratio (example: D:S = 90:1). Form factor including size and weight (example: pistol grip form factor, <1 kg). Radiometric accuracy (measures absolute, calibrated temperature; example: ±2°C or 2percent). Temperature measurement range (example: -10°C to 250°C or 14°F to 482°F). Image and data storage capacity (example: internal flash memory stores 100 images and orresponding data). Battery life (example: five hours in continuous use). Length of warranty (example: one year.)
Array size and type -- The larger the array, the more resolution (pixels) in the thermal image. Costs for imagers are directly proportional to the size of the array, since these components contain the core infrared imaging technology. While larger arrays do, typically, produce nicer images, for predictive maintenance customers the picture quality from a 160x120 array is more than sufficient in most applications.
Thermal sensitivity or NETD -- This is the smallest temperature difference the thermal imaging camera can resolve. 200 mK or 0.2°C indicates that the camera can resolve two tenths a °C temperature difference. Some cameras can resolve as little as one tenth or half a tenth °C temperature difference. Again, these cameras produce very high quality images, but also, typically, come with a higher price tag. For maintenance applications, there are very few applications, if any, requiring the ability to resolve less than 0.2 °C temperature difference.
Field of view and Optical Resolution -- The optical system in an infrared camera has a limitation to how much the camera will asee' of a given object at a given distance. This is determined by the field of view. If many of the applications involve small objects (<2inches in diameter) at large distances (50or100feet), then a narrow field of view (12°x9°) with a larger D:S (>250:1) will be required. If many applications are close up looking at large objects (electrical panels in narrow passage ways or building inspections), then a wider field of view (40°x30°) and smaller D:S (60:1) may be required/sufficient. For most maintenance applications (both electrical and mechanical), a field of view between 16°x12° and 30°x22.5° is appropriate; especially if there is flexibility with most inspections to move closer to or farther away from the target. D:S performance of 75:1 or higher is also usually sufficient, although some smaller electrical components may be difficult to measure accurately at this level.
Form factor -- It is important not to underestimate the form factor, size and weight of professional tools. Thermal imagers should be comfortable to carry around and use all day long. They should be well balanced in the hand, easy to grip and lightweight. This overall ease of use factor could mean the difference between the tool sitting on the shelf or constantly being in use on the factory floor.
Radiometric accuracy -- Some very low cost imagers are non-radiometric or only partially radiometric, meaning the pixels are not measuring an absolute temperature. They are only showing temperatures relative to one another. So while a hot spot might be visible, the camera cannot tell you what the real temperature of the hot spot is. This is a significant disadvantage in PdM applications, where so much of the equipment being inspected will have rated operating ranges for temperature. Also, trending of temperatures over time is only possible if the imager measures absolute temperature.
Temperature measurement range -- The needs for temperature are a direct correlation to the applications present within the industrial environment in question. In most manufacturing and facilities environments, the temperature range needs for the electrical and mechanical equipment will not exceed 250°C. However, in the metals industries and some others, temperatures over 250°C are quite common. If this is the case, a camera with a higher temperature range may be necessary. If the higher temperature requirement is more of the exception than the rule, this may be where an outside consultant can help supplement an internal programme.
Image and data storage capacity -- Internal memory has some advantages over external options such as memory sticks or flash media cards. In most environments 100 (oreven50) memory locations is sufficient to support a full day of uninterrupted inspections.
Battery life -- With batteries, think convenience, cost and reliability. Does the camera's battery life provide for a full day of uninterrupted inspections? This will require only four or five hours of continuous use battery. The discharge time should also be at least three times faster to charge the battery as it is to discharge, otherwise you will need multiple batteries and chargers, which can be quite expensive. Is there a convenient power option besides a customer rechargeable battery pack? It can often be a life saver if off the shelf" alkalines can be substituted instead of the custom rechargeable battery pack.
To summariseit is important for companies to invest in a thermal imaging camera that fits their needs. This means the camera should be appropriate for the majority of their intended applicationsbut not be over specified or loaded with complicated and expensive extras. These high end specifications and extras will definitely increase the up front investmentso it is important for the decision maker(s) to validate the company's true needs.
Thermal imager accessories
Before purchasing a thermal imaging cameraconsider the additional accessories that may be needed. Depending on the battery lifeextra batteries and charging stations may be needed to get through a full day of inspections. Extra batteries can cost several hundred dollars a piece. Also consider the need for a transport/carrying case. Buying a camera with optional lenses provides a more flexible imaging solutionbut it is also significantly more expensive. Make sure the optional lenses are truly needed and will be used. Ideallythe company will receive everything they need in one convenient packageand they will not have to buy very many extras to get started.
There are various software solutions availablewhich accompany thermal imaging cameras. Some software is very basiconly showing images (picture files) with no ability to analyse data or even create a report. Some software will store and analyse data and create reports. Some software will also integrate with other PdM technologies and even automatically generate work orders in the CMMS system. Againunderstanding the company's needs is critical to making the correct choice. With some of today's affordable thermal imagersadvanced storageanalysis and reporting software is provided at no additional chargeas part of an overall PdM solution.
For predictive maintenancehaving the ability to analyse images and data and create reports is very important. Sometimesjust seeing the image is not enough to make a determination of the existence and/or cause of a problem. Alsoadvanced software packages provide additional flexibility to the end user while in the field. If the end user sets the wrong emissivity or gets back to their office and wants to see an image in a different palettethis is no problem. They do not have to go back into the field and retake the image. The software allows them to change the image and data settings after the factin the comfortquiet and safety of their office.
Another consideration for software is whether there is a license agreement. Can the software be loaded on unlimited PCs or does the company have to pay a license fee for each additional user? Alsowhat about software upgrades?
The investment for thermography software can range anywhere from afree' to thousands of dollars for each individual user. Once againmatching the needs of the company/applications with the solution is very important to make sure the investment will generate the maximum return in the shortest period of time.
Training is an important consideration when starting any new initiative or improvement programme. Predictive maintenance and thermal imaging are no different. In order to maximise the return on investment in camerasaccessories and softwarethe engineerstechniciansmechanics and/or electricians must be trained on: How to use the equipment. What applications will provide the greatest return on investment. The limitations of infrared inspections based on the laws of physics. How to properly perform inspections to achieve consistent and reliable results. How to interpret results and generate meaningful reports. How to safely conduct thermography inspections in an industrial work environment.
Some manufacturers of infrared cameras provide free training with the purchase of the thermal imager. This training may only cover the basic use of the camera or it may be more involvedtouching on applications as well as best practices for establishing an effective infrared PdM programme.
Before making any investment decisions in thermal imaging equipmentconsider the ownership costs associated with service and calibration over the life of the instrument. There is a very wide range of costs from camera manufacturers for basic service and calibration of thermography equipment. Depending on the brand and model of cameracosts for an annual calibration could be as little as $350 or as much as $2000.
Once the programme is up and runningthe effort involved to collectstoreanalyse and report on the data is also significantso it is helpful if the thermal imager being used supports the concept of inspection routing. This allows electricians and mechanics to easily gather the data on their ownfreeing the expert to manage the overall programme. Initially the workload will be greaterbut if the programme is well designed and executedvery quickly the PdM approach will take less maintenance and production manpower and resourcesthan a run it until it breaks approach.
Maximising the return
The benefits of investing in thermal imaging equipmentsoftware and training and implementing an in-house infrared PdM programme include: Eliminating existing expenses such as annual or semiannual thermographic inspections by outside consultants. Reduction in unnecessarypreventative maintenance activities. Improve maintenance efficiency and reduce unplanned downtime. Reduce capital equipment expenditures by increasing the life expectancy of capital equipment. Improve production efficiency and quality.
Many companies hire external consultants (rates may range from $750 to $1500perday) to inspect their facilities on an annual or semi-annual basis. By bringing the inspections in-houseunnecessary fees and repairs can be eliminatedin addition to the consultant fees.
Predictive maintenance techniques are used to assess the acondition' of the equipment before taking maintenance actions. In this wayactions are only taken when the machine's condition warrants the actionnot before. There are even cases where preventive maintenance actionsif taken too soon or too oftencan actually lower performance levels. Applying grease to bearings should be done somewhat regularlybut if greasing is overdonethe bearings can fail prematurely.
While a thermal imager is considered the ideal tool for predictive maintenanceit is also very useful as a troubleshooting tool. For examplewhen rotating equipment seems overloaded or is too noisyinspecting the equipment with a thermal imager can help identify a heat signature and more importantly a source.
Finallysafety is also an important benefit when using a thermal imager. Because thermal imaging is a non-contact technologyusers can stay out of harms way while inspecting alive' rotating equipment.
As with any predictive maintenance technologythe ultimate goal is to keep equipment up and running. This means we must reduce the amount of unplanned downtime. Unplanned downtime leads to many problems for a production facility.
The final benefit to consider when implementing infrared predictive maintenance is simply the increased lifetime of capital equipment that can be achieved. If the average life time of equipment for a company is 10 years and the total value of that capital equipment is $1000000then the company ison averagespending $100000 per year to replace aging equipment. If the average lifetime can be extended by 10percent due to improved maintenance practicesthen the annual costs to replace aging equipment drops to $90000peryearsaving $10000 each year in replacement costs.
With the proper knowledge and toolsmaintenance and reliability managers can easily justify the implementation of an infrared predictive maintenance programme. A thermal imager with the necessary accessoriesPC software for storage analysis and reporting and professional thermography training form the critical components to any effective infrared predictive maintenance solution.
Before making any investments in thermographycompanies should thoroughly assess their critical equipmentapplications and organisational needs. Only thenshould they investigate the products and solutions available.
The market is changing rapidly and products are becoming more affordable all the time. For most companiesthe benefits of an effective PdM programme using thermal imaging will far outweigh the initial investment.
Jason R Wilbur is Thermography Segment ManagerFluke CorporationSanta CruzCAUSA. www.fluke.com/ape_imager"