While conventional smoke detectors in offices usually reliably prevent the occurrence of fires, other detection techniques must be used whean roasting coffee. The high temperatures that arise during the roasting process in connection with impurities can lead to the development of embers in the roasted coffee, which then enter the cooling sieve after the roasting process is complete. In the least critical case, the quality of the respective roast batch is impaired as a result. In the worst case, however, such embers can lead to a fire in the cooling sieve or in a downstream unit.

For early detection of such hotspots, the coolers of PROBAT roasters can optionally be equipped with temperature sensors in the form of infrared thermal imaging cameras. Their functional principle is based on the emission properties of objects in the infrared range of the electromagnetic wavelength spectrum. This varies in intensity depending on the absolute temperature of the object. PROBAT thermal imaging cameras operate in the mid-infrared range and are therefore particularly suitable for detecting incipient or imminent fires caused by embers in roasted coffee. They enable a sensitive evaluation of temperature inhomogeneities or differences. They permanently monitor the bulk material surface formed by the roasted coffee beans in the cooling sieve. In the roasting machine control system, in which the camera data are integrated, different limit temperatures are set for different cooling process times. In the event of local overheating with temperatures above a defined limit value, suitable countermeasures can be initiated depending on the degree of overheating. An alarm is triggered if the temperature is exceeded for at least three seconds.

At the same time, the thermal imaging camera records a video during the cooling process, which is saved and assigned to the respective roasting batch so that a separate quality check of this batch can take place. If the cooling process runs without an alarm, the video is overwritten. The control system can also be used, for example, to set markers with different priorities depending on how long the respective limit temperature is exceeded. In this case, an alarm is only triggered at the first priority level. At the second priority level, no alarm is triggered, but the operator is informed that the quality of the roasting batch should be checked. If the limit temperature is minimally exceeded, which could be due to soiling of the cooling sieve, for example, this message is then only stored as information.

Thanks to their extremely precise detection properties and direct integration into the roasting machine control system, PROBAT thermal imaging cameras guarantee consistently high product quality and maximum process reliability.