Infrared sensors suit predictive maintenance and safety-critical tasks

Paul Boughton

Temperature is one of the best indicators of a fault or malfunction in virtually all electrical or mechanical equipment. However, key electrical switchgear has traditionally proved very difficult to monitor, being inaccessible within metal enclosures.

Over the last decade, the accepted preventative method of reducing the risk of key electrical switchgear failure has been periodic thermal imaging, but it is not ideal.

Firstly, thermal imaging inspections are normally only periodic, (typically once or twice per year), due to the high costs/time involved.

Secondly, thermal imaging is carried out externally to the switchgear enclosure, so only the components immediately adjacent to the external panel can be inspected. Thermal 'windows' improve the situation, but still require direct line-of-sight to the target. The answer is to have a predictive system, actually inside the cabinet, directly and continuously monitoring all key components.

Exertherm is a novel system from QHi-Systems that is based on patented small, low-cost, plastic-bodied, non-contact, infrared sensors, which require no external power source – so allowing the sensor to be placed inside the enclosure to continuously monitor any component, irrespective of its location. And because the non-contact infrared sensors require no power, (just like a normal contact thermocouple), they do not require an amplifier. As a result they have lifetime calibration. In contrast, other IR sensors require power, meaning that panels have to be opened regularly and sensors accessed for re-calibration.

Exertherm sensors also have exceptional reliability, with an MTBF of over 1000 years, and they require no maintenance. Put all these features together, and it means a true ‘fit and forget’ product.

Though originally designed to monitor electrical switchgear, virtually all key plant (anything which increases or decreases in heat as a symptom of fault or malfunction), can also be continually monitored. Sensors are linked back via data acquisition cards to a PC or server, to provide on-going trend analysis, graphs and reports. Further protection is provided via two separate alarm levels per sensor (warning and alarm), which automatically activate in the event of pre-set temperature levels being exceeded.

Other features of the system include: suitable for new, retro-fit/expansion, easy and inexpensive integration with over 400BMS/bus protocols, available via LAN, WAN, internet, intranet, etc.

This new technology has already been  installed with many organisations in telecommunications, computer data centres, shipping, and large-scale manufacturing. For use in hazardous areas, the Exertherm sensors are also classified as ‘simple apparatus’. 

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