Camera ready?14 May 2013

With the plethora of thermal imaging cameras available today, users could be forgiven for believing training was a non-issue. As Brian Tinham explains, nothing could be further from the truth.

'Twas the time when thermal imaging was an expensive novelty technology, aimed exclusively at skilled, professional users working in niche markets that could afford them. Not anymore. Now, anyone can buy an infrared camera – and from a spread of companies cashing in on the growing demand for these increasingly popular temperature sensing, recording and analysis instruments.

What's more, devices are available not only for mechanical and electrical plant inspection and condition monitoring, but also for anything from machine vision to intruder surveillance. Focusing on the former, though, their popularity stems from their sheer usefulness.

Clear benefits include: their ability to provide for non-contact and non-invasive temperature measurement, making them ideal tools for predictive maintenance; their apparent ease and speed of use, and safety, compared to other fault detection and condition monitoring techniques; and their ability to solve plant access problems by remote monitoring, especially around live electrical equipment.

Less obvious, perhaps, but they also lend themselves well to periodical inspections of plant under the same operating conditions or running under full load, so minimising production interference. Equally, they can significantly reduce the time and cost burden of routine maintenance inspections, so increasing productivity and profitability.

There's no shortage of product choice. At one extreme, lower-cost hand-held equipment is readily available online, often with promotions, discounts for trade-ins, and special-offer ex-demo units, just like any other commodity. And there's nothing wrong with that. At the other, specialist devices – such as CorDex Instruments' new intrinsically safe (IS) infrared camera, for ATEX-classified hazardous areas – are still emerging.

With the latter, there's still a commodity feel, with the emphasis remaining on ease of use as well as fitness for purpose. However, price tags for high-end instruments reflect their considerable development and certification costs, and relatively confined markets. So such cameras are not for the 'casual' user.

That said, therein lies a lurking problem. In fact, none of these cameras is, strictly speaking, appropriate for casual users. Without considerable training, it's easy to misinterpret temperatures the camera apparently 'sees'. The unwary could report excessively high (or low) temperatures, due to a failure to consider emissivity and/or reflections.

As Mark Ely, product manager for thermographic imaging equipment at SKF, explains, surfaces' emissivity (their relative ability to emit radiative energy) depends on the material. "Maintenance technicians might point their cameras at bright, shiny bearings, and then be surprised when they get substantially wrong readings. We advise a couple of simple solutions. They can either set the emissivity on the camera to match the surfaces they're interested in [they're generally set at 0.956, which works for most non-reflective surfaces], or they can apply adhesive tape, where this isn't going to affect plant performance or cause a hazard." Obviously, not on bearings.

Both techniques work but, as Ely points out, they may be unnecessary if all that's required is detecting a temperature difference on, say, copper busbars and connectors, where the objective is to find faults before they lead to unplanned downtime or become dangerous. The issue is invariably one of comparing apples with apples – and understanding that absolute, as opposed to comparative, temperatures are so often not required. "When it comes to maintenance, it's better to use thermal imaging cameras to detect temperature anomalies than to get fixated on exact temperatures," comments Ely."

Much the same applies to cameras picking up thermal energy reflected from surfaces due to sources nearby – or even the sun. And other pitfalls include misconceptions around precisely what infrared can see through – so 'yes' to some smoke, but 'no' to solid surfaces. Your technicians are not, for example, going to see excessive heat emanating from pinions or bearings inside gearboxes; they can only infer a problem through the heat transferred to the external surface of the gearbox casing.

So, buyer beware: you're purchasing the instrument because you need the insight it can deliver, so you need also to invest in some serious training, if you don't want to be disappointed. Also, remember the importance of fitness for purpose.

Brian Tinham

Related Companies
CorDEX Instruments Ltd
SKF (UK) Ltd

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