This type of equipment employs an infra-red camera and produces a thermal image (photograph) which may be either directly observed or computer analyzed for anomalies.
Thermal imaging is a very useful tool for monitoring static bunkers and silos; however, it is not usually practical for conveyors, as imaging scan times are too slow for fast moving belts.
 

These are designed to detect sparks and very small visibly glowing embers. These types monitor for short IR wave lengths that are at or near the solar band and are mainly intended for installation in ducts where there is a zero level of ambient lighting.
Spark detectors are not solar blind and the IR filters (e.g. 0.4 to 1.6 microns) do not permit detection of IR emissions from relatively low temperature abnormalities such as pre-ignited PRB coal.
 

Many of these types monitor for the peak IR emissions, associated with specific gases, that occur during combustion. These emission spectra are not the same as for “black body”radiators as defined by Planck.
E.g. for C02 formation a peak occurs at 4.3 microns which may be compared with specific narrow bands where little (CO2) emission occurs.
Other types filter shorter wavelengths, similar to spark detectors (e.g. 0.7 to 2.7 microns), and apply analysis to detect “flame flicker”. These techniques monitor for volatile fluids and gases after “flash point” and are not suited for close range monitoring of moving bulk materials such as coal when on fast moving conveyor belts.
 

This infrared sensor type employs IR filters that select longer wavelengths (eg >5 micron) and is truely “blind” to the visible spectrum. These detectors can register both the high energy emissions from very hot / burning material, and those from abnormal but relatively low temperature bulk coal transiting the monitored belt area. This performance band encompassing "glowing ember" detection.

It is this type of detector that is best suited to Coal Conveyor monitoring.
 PATOL 5000 SERIES ARE BLACK BODY HEAT DETECTORS