Low-cost thermal imaging in plant maintenance

Paul Boughton

Thermal measurements help detect imminent failures in nearly all types of equipment, from electrical to mechanical, process, electronic and so on. Ken West reports

Thermal imaging is gaining an invaluable predictive and diagnostic reputation in plant maintenance and process applications. No longer a specialist tool,  are affordable for everyday use and operate in a similar way to digital cameras: an LCD display shows the IR image as the user selects the view, focuses, then squeezes the trigger to record the image.

As a regular maintenance and troubleshooting tool, one particularly strong asset of thermal imaging cameras is that they are 'non-contact' tools: not only are maintenance personnel at a safe distance from electrical infrastructure and hot or moving machinery, but also there is no need for plant shutdown while personnel carry out measurements.

Fast and predictive

Thermal imagers provide very fast, multiple point temperature measurements of a scene. They are suitable for moving targets and machinery, hazardous and inaccessible or distant targets, electrical components, 'big picture' evaluations of machinery or surfaces, and also for trending records.

Thermal imagers can access components and units not otherwise measurable, such as ceiling runs. In most cases, the surface temperature at specific points of critical plant assets is a consistent indication of its operating condition.

Thermal measurements help detect imminent failures in nearly all types of equipment, from electrical to mechanical, process, electronic, and so on.

Because thermal inspections are fast, they can cover more ground and find problems in areas that would typically be ignored.

Qualitative analysis of infrared data can be used as an effective predictive maintenance tool.

Affordable and easy-to-use

Today's industrial maintenance thermal imagers are compact and easy to use with minimal training. Prices are such that a thermal imager is affordable as an everyday maintenance tool, no longer the preserve of an outside specialist. If the user already carries out regular maintenance and troubleshooting, adding thermography (the application of thermal imaging) makes sense.

Which units are critical to performance are already known.

A thermal imager will then also be part of the kit when troubleshooting, and during installation of new equipment.

Invisible to our eyes, IR radiation is heat radiated by or reflected from a material. A thermal imager interprets the radiation by assigning a visible graduated colour to the scene.

The colour palette displays hot spots as white with diminishing temperatures through red-orange-yellow-green-blue-indigo-violet to black being cold. This enables a visible representation of the unseen IR spectrum. In addition to highlighting temperature variations and hotspots in real time through the LCD display, the ideal cameras marry high-precision thermal images with visible light images in full screen, picture-in-picture or blended views, for enhanced problem detection and analysis. These cameras are able to download recorded images to a computer, for further analysis with the provided software, and for saving in a comparative database.

Spot temperatures

Within the computer program, the image can reveal specific spot temperatures, a grid of temperature readings, minimum-maximum-average temperatures of a specifically selected area of the image, emissivity and reflectivity can be adjusted, level and gain can be adjusted, the palette can also be changed, and more. The software can then be used to create the required reports, documenting the findings.

Applications

- Motors, pumps, fans, compressors, bearings, windings, gearboxes, conveyors, etc. Thermal inspections of the bearings, shafts, casings, belts, gearboxes and other components that emit heat before failure occurs can prevent the unexpected equipment breakdowns of moving equipment.

- Power distribution systems. Thermal imaging can identify bad electrical connections, imbalances, overloads, harmonics, and other impending electrical equipment failures, and prevent uneven or inadequate power supply as well as downtime.

- Process control equipment, pipes, valves, steam traps and tanks/vessels Paper, glass, steel and food product production all require the uniform application of heat. Portable thermal cameras can be efficiently used to troubleshoot problems and determine the optimum spot to install a thermocouple or infrared sensor.

Fluids need to be delivered to the right place at the right time and in the right amounts: a thermal image can often pinpoint an obstruction in pipes, allowing corrective action before the whole loop goes down.

Process control valves are also critical to delivering fluids to processes at the right time: here a thermal imager can be efficiently deployed in order to to monitor for evidence of leakage, sticking or excess friction.

Thermography can help to identify failed steam traps and whether they have failed open or closed. In general, if a thermal image shows a high inlet temperature and a low outlet temperature, then the trap is functioning correctly. Any other combination indicates the possibility that a potential problem could occur.

- Facility maintenance - Buildings, roofs, insulation, heating, ventillation and air conditioning (HVAC) systems.

Here, thermography can be used to identify a whole range of energy issues, including missing or damaged insulation, air leakage, moisture intrusion in roofs and walls, actual and potential mould areas, thermal bridges and water leakages.

Ken West is UK Regional Marketing Manager - Industrial Tools, Fluke (UK) Ltd, Norwich, Norfolk, UK. www.fluke.co.uk.