The latest generation of infrared thermometers combines affordability, precision measurement and photo documentation to enhance preventive maintenance and quality assurance like never before. Scott R Williams reports.

While surface temperature is often a good indicator of how well your equipment or process is running, regular temperature measurement should be an essential element in any preventive maintenance, industrial process control, and quality inspection effort. There are essentially two methods of temperature measurement - through contact with a measurement probe or at an optimal distance utilising infrared technology.
Non-contact, infrared temperature inspection tools are by far the better choice for industrial applications, because of their greater accuracy and ability to measure hot, moving or hard-to-reach surfaces from a safe distance. A thermometer probe requires you to come into contact with the surface, which can alter its temperature, or otherwise tear or contaminate the product you are measuring. IR thermometers also enable several readings per second, allowing users to be more productive compared to contact methods whose measurements can take several minutes.
Regular temperature monitoring with IR thermometry is vital for proper condition and quality monitoring, and can actually lead to the reduction of maintenance costs on mechanical equipment as well as product waste during production. This is because such temperature evaluations help technicians zero in on problem areas, expressed in unusual rises in temperature, and focus problem-solving diagnosis more effectively.

Infrared thermometry basics

Here is how this non-contact measurement solution works: The IR thermometer measures the infrared energy that is naturally emitted from the surface of all objects. Pointed at the measurement target, the instrument captures this energy as it passes through the atmosphere, directs it through its optical system, and converts it into an electrical signal, which is translated into a temperature reading. This signal is displayed instantly in degrees Celsius (or Fahrenheit) on the unit's LED readout, or in tables and graphs on a PC with the help of companion software. Such technology in the form of automated line scanning systems (Fig. 1), which provide a two-dimensional thermal image of product surfaces, has been widely used reliably in industry for years to to keep an eye on critical processes. In addition, handheld models are increasingly becoming the tool of choice for hot-spot detection during routine maintenance inspections of production equipment.
All mechanical systems generate thermal energy during normal operation and temperature monitoring can evaluate their operating condition. One of the biggest problems in mechanical systems is excessive temperatures. This excessive heat can be generated by friction, cooling degradation, material loss or blockages. An excessive amount of friction can be caused, for example, by wear, misalignment, or inadequate lubrication. Regular temperature monitoring of machinery components enhances a company's ability to predict failure and plan corrective action before a costly shutdown, equipment damage, or personal injury occurs. Temperature checks should be performed regularly to locate hot spots or heat imbalances on, for example, drives and motors, bearings and transmissions, as well as hydraulic components, pumps, pulleys, and conveyors.
However, simply identifying a change in temperature does not necessarily mean a problem has been located, because most production machinery is designed to give off thermal energy during normal operation. This machinery has normal operating temperature limits that can be used as guidelines by the maintenance technician. Scanning the surface of machinery components with an IR thermometer - by pointing it at the target, holding down the trigger and moving the thermometer up and down, side to side - quickly identifies unusual temperature variations and hot spots outside the normal operating range. Since temperature readings are repeatable, multiple measurements of the same objects over time can show condition trends and help technicians plan ahead for maintenance and repair, before critical components or systems shut down.
Important criteria for the use of any measurement instrument in industrial maintenance or quality control applications include simple, uncomplicated handling, as well as high accuracy and repeatability. There is a variety of handheld infrared thermometers currently available that meet these requirements. These lightweight units are often small enough to be hooked to a tool belt. Most IR thermometers include laser sighting to help quickly locate small targets from optimal distances, even in low-light conditions. The temperature of targets as small as 6mm can be measured from distances of a few inches from the target; larger spot sizes can be measured from several meters away. This space between the user and the object becomes critical when examining problems involving high voltage, moving, or high-temperature surfaces.
In addition to the demand for greater accuracy and repeatability, there is a growing requirement for data logging and visual documentation. When a critical temperature or a hot spot is found, a need is arising to document it in a way that provides more information than just a temperature reading. Fire safety inspection, equipment maintenance, food safety, and production quality applications, for example, require visual proof that the measurements have been performed. The reduction in size and cost of digital cameras with sufficient memories now allows the complete integration of visual imaging functionality into the modern IR thermometer. In addition to circular laser sighting techniques, which indicate the true spot size at any measuring distance, these new photographic IR thermometers become an important tool to prove when, how and where measurements were taken. A USB interface allows fast image or video sequence downloads to a PC. Companion software enables information about temperature, time/date and exact spot location to be included in the image.
By utilising these latest tools for temperature monitoring, maintenance and inspection professionals can use real-time images to clearly and effectively communicate with management, equipment manufacturers, and service personnel about maintenance/repair and quality issues. Service providers can create permanent visual inspection records indicating temperature behaviour before and after repairs.
The detailed images can be included into inspection reports to document the current state of equipment, trend its condition over time, and to offer recommendations for panning future repair work and inspections. l

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Scott R Williams is European Marketing Specialist with Raytek GmbH, Berlin, Germany. www.raytek.com