Effective monitoring
January 1st 2007

Thermography is now becoming a standard tool for the maintenance engineer now that it has become affordable says Sat Sandhu, IRISYS

Thermal imagery, the technology that looks at the world in terms of temperature, rather than visually, identifying hot – or cold - spots on or within surfaces that are not visible to the naked eye has been around for 30 years or more, but until recently its use was restricted because of its prohibitive cost.

It was used mainly for military applications, particularly for tracking aircraft, although specialist consultants and thermographers later took it into the commercial markets by offering outsourced services to the wide sphere of industry and commerce that would not entertain purchasing the technology on cost grounds. Imagers were priced between £30,000 and £50,000.

However they were perceived to be a highly flexible tool that could make a great contribution to a wide range of industry if only the purchase price could be brought down.

Roughly seven years ago a rapid advancement in thermal imaging technology brought about significant reductions in the products' cost and this, combined with increasing awareness of the benefits of thermography, led to increased volume purchasing and price reductions A number of manufacturers brought about a revolution with the production of low cost, low resolution imagers that took the market by storm. With a 16X16 array the imagers were quickly taken up by engineers and contractors who were looking for a quick way of identifying and fixing equipment such as fuses, bearings etc.. that were showing signs of failure .

Some of the new generation of imagers were capable of measuring up to 256 temperature points simultaneously over an object or area, at a price which was significantly lower then a line scanner, and similar to that of a few of the higher performance singlepoint radiometers.

Consequently a large number of industrial companies have been using them very effectively over the past few years as any manufacturing process that is temperature sensitive – or any plant that falls within a planned predictive maintenance regime – can be thermographically monitored to ensure that user-defined thresholds are not exceeded.

The technology has been used for identification of loose or overtight electrical connections, over twisted wires, overloaded components, uneven voltage distribution and failed or fatigued components – all problems cause changes in temperature.

From a mechanical perspective, thermography identifies faults in bearings and motors due to poor lubrication and/or shaft alignment leading to excessive friction… and a rise in temperature.

Set up is easy and, once positioned, imagers require little ongoing attention – a benefit that is particularly important where access is difficult or measurement is to be carried out for long periods.

Having appreciated the benefits of low resolution imagers many plant and maintenance managers asked for more. They were particularly keen on higher resolution, more ergonomically friendly units (the first generation were heavy and unwieldy) and with more sophisticated benefits.

The result was launch last year of a new series of thermal imagers, making the market has become awash with midrange products, all offering enhanced features at varying prices.

Smaller UK based manufacturers are taking on the foreign-based market leaders with products that they believe offer all the "whistles and bells" at comparable prices.

Features now available to engineers include: measurement and recording of temperatures from -10°C to +250°C with a pixel resolution of 160 x 120 that gives crisp, high resolution images through the incorporation of a big 3.5" colour LCD display with LED backlight; storage and retrieval at full digital resolution of up to 1000 high quality images on the supplied SD card; two measurement cursors to highlight temperature and temperature differences; a Class II laser focuses on the central measurement area for ease of identification of specific hot spots; A 20° x 15° field of view lens with a minimum focus of 30cm, and fitted with manual and auto functions for image adjustment; an evenly balanced weight of 750g (including the four-hour capacity, field replaceable battery).

The new generation of imagers has been of particular interest to the plastics industry which found the low cost thermal imagers beneficial for monitoring product as it comes out of the mould, identifying hot or cold spots on the product to demonstrate the quality of the moulded product and also an indication of the condition of the mould.

Furthermore thermography is already playing an important role in food manufacturing with their wide variety of specific heat related operations, including monitoring and control of temperature critical product to prevent melting, sticking or clogging on conveyors and subsequent handling problems.

Thermal imaging is a rapidly evolving technology that is destined to play an increasingly important role in process engineering, and giving British business generally the opportunity to embrace 21st century technology and maintain a cutting edge in worldwide industry and manufacturing.

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