Thermal Imaging

By the use of a modern focal plane array thermal imaging camera, and expertise in its use, it is possible to survey materials and equipment to detect changes in temperature and to record these images for further analysis. Modern imaging cameras are light, portable and easy to operate and offer excellent image clarity. This has ended the previous practices of capturing a polaroid film image alongside the thermal image to aid in the diagnosis and reporting of faults.

The applications of thermal imaging are many and various, but can be summed up by the detection of temperature change in a material or zone which may by the application of knowledge lead to the detection of faults, real or potential.

It is this application of experience which can be of truly great benefit in the detection and quantifying of problems.

Some uses for Thermal Imaging

Fault detection in electrical distribution networks.
Misalignment of chain drive systems.
Fault detection in large generators by energising of the stator core with the rotor removed during maintenance.
Valve failure in compressors.
Study of boiler insulation wear and the erosion and blocking of boiler tubes.
Breakdown of refractory material in furnaces.
Fault detection in overhead power lines on electrically powered railways.
Insulation failure in pipelines.
Lubrication problems in bearings and gearboxes.
Leaks of product from pipelines.
Faulty or loose drive belts.
Energy loss in buildings.
Fire detection in waste dumps.
…… and many more.

Thermal Imaging Practical Examples

Note the elevated temperature (around 60 degrees) of the central cable on the upper section of the 'Siemens' contactor. A perspex shield prevents a clear view of the area, but a loose connection is suspected. Advise check security of upper connections on this contactor. — Note the elevated temperature (around 60 degrees) of the central cable on the upper section of the ‘Siemens’ contactor. A perspex shield prevents a clear view of the area, but a loose connection is suspected. Advise check security of upper connections on this contactor.

The temperature of the trip Q 14 is around 100 degrees Celcius. None of the connecting cables appear to be operating at high temperatures suggesting the fault is internal.

This image is of the main isolator in an electrical control panel. Note the elevated temperature (+10 degrees compared to the other phases) of the upper connection 'blue' phase. The temperature gradient suggests a poor connection. — This image is of the main isolator in an electrical control panel. Note the elevated temperature (+10 degrees compared to the other phases) of the upper connection ‘blue’ phase. The temperature gradient suggests a poor connection.

Use of Thermal Imaging: A Case Study

A survey was required for a hardboard manufacturer in the basement area of a large ‘press’ to try and establish whether any hydraulic faults were apparent in the valvegear.

A recurring problem with the press suddenly opening during the compression stage had been occurring with increased frequency.

During the test it quickly became apparent that valve ‘C’ was bypassing significantly, the temperature of the return pipe rose from around 23 degrees to in excess of 32 degrees.

Little change in temperature was noted from the other five valves.

The valvegear and surrounding equipment were scanned prior to and during the test. The ambient temperature was approximately 20 degrees Celsius. Whilst the temperature of all the valves rose to around 25 degrees (working fluid circulates above the valves during compression), only valve ‘C’ indicated any significant change in the temperature of the return pipe (rising to above 32 degrees).

Images of all the valves were recorded and samples are reproduced below. Note also the image of the return manifold which also clearly indicates that working fluid (normal temperature around 38 degrees) is flowing in the return from valve ‘C’.