What is the best location to detect hot material on a coal or biomass conveyor?

An infrared linescanner is an excellent tool for detecting potentially dangerous hot material on a conveyor belt. It works by repeatedly scanning across the width of the belt and using a calibrated infrared sensor to measure the temperature of the moving material. If it detects a hot inclusion such as a smouldering piece of coal, it can alert the process operator who can then take appropriate action. Such action could be to divert the material or to activate a deluge system.

Regardless of the material or the remedial action, it is important to choose the best installation location. This isn’t a trivial matter as several factors must be borne in mind. 

What is the best location to detect hot material on a coal or biomass conveyor?

VIEW - Perhaps the most obvious is that the scanner must have a clear view of the material on the belt, so there must be no obstructions in the field of view. If the belt is enclosed, it will be necessary to find (or create) a gap in the cover. 

DISTANCE - The distance between the belt and the scanner is also important. The AMETEK Land HotSpotIR infrared linescanner has an 80° scan angle, so the width of the scan is 1.68 times the distance between the scanner and the belt. For a 1.2 m belt, this means the scanner must be at least 0.72 m above the belt if it is to monitor the full width. Increasing this distance slightly is acceptable, but an excessive distance will reduce the spatial resolution and so decrease the effectiveness of the monitor. As a general rule, the distance between the belt and the HotSpotIR should be between 0.6 and 1.2 times the belt width.

POSITION – It is generally acceptable to mount the scanner directly above the belt so that it views the surface of the material being transported (Position 1). Because it uses infrared energy to measure the temperature, it cannot detect a hot inclusion lying beneath the surface. It is not entirely possible to get around this limitation, but a partial solution is to mount the scanner at a transfer point where the material spreads out and it is possible to view through it (Position 2). There are some cases where the item of interest is the belt itself rather than material being transported. In such cases, it is best to view the belt on its return path just after the transfer point (Position 3).

Find out more about the HotSpotIR infrared linescanner for conveyor belts.

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