Inspection Methodology

Thermography is becoming one of the fastest growing predictive maintenance technologies available today.  The development of hand held focal plane array based systems enables predictive maintenance engineers to bring the thermographic camera to virtually any equipment site with ease.  Advanced image processing and reporting programs facilitate fast and easy analysis and documentation of survey results.

Typical surveys are conducted by first compiling a “route list” of equipment to be inspected in a facility. This route list is then used to generate a Risk Assessment and Survey Method Statement   The route may contain a variety  of different equipment types, which will exhibit different thermal characteristics when deteriorating, and may require input from the manufacturer to obtain critical temperatures for repair category classifications. Therefore even before the inspection starts all repair categories are in place and any data required from a third party will have also been obtained.

Examples of inspection requirements include:
• Electrical equipment, which will show hot connections as a result of corrosion, loose connections or thermal build-up from phase imbalance or overloading.
• Mechanical systems may show signs of overheating due to poor bearing lubrication or shaft misalignment. 
• Refractory linings or other insulated objects may show growing areas of thermal loss due to poor or deteriorating insulation.

Engineers may use the generated images to monitor the progress of corrosion in piping systems or on storage tank floors or walls.
Most of these objects are inspected routinely with an eye towards looking for significant changes in the thermal characteristics since the last survey. The frequency of which the surveys are performed varies greatly depending on the relative importance of the device being monitored and the resources available to the maintenance team.

Typically problems manifest themselves in two ways.  With electrical and mechanical components, the problems appear as hot spots, which gradually grow in temperature.  With insulation/heat loss related problems and NDT studies, the problems manifest themselves as thermal patterns, which grow in size.  In some situations, both the temperature and the size of the thermal pattern will increase.