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Greater safety for waste bunkers
and conveyor systems

Early warning fire detection and tracking

In waste bunkers of incineration plants where RDF (refuse derived fuels), municipal waste and / or commercial waste is stored, there is a high risk of fire. For an increasing number of these facilities, therefore, early warning fire detection systems (according to the 17th Federal German ruling on emissions control - 17. BlmSchVl) are required by law and have become standard. More and more insurance companies recommend such a risk reducing measure, and some actually insist their clients install these systems. Our respective infrared camera systems have been operational in Germany, Austria, and Switzerland for over twelve years, now.

ThermoObserver 1.1 – fire alarm system for bunkers of waste incineration plants
An microbolometer infrared camera fixed on a pan/tilt head scans the waste surface in the bunker measuring the temperature and detecting hot spots (fire sources). When the set temperature limits are reached, alarm is given. To achieve this, the ThermoObserver software continually analyzes the infrared camera’s video signal in real-time. In order to cover the complete bunker surface, and to allocate the data, the waste area is divided up into individual grid zones. Temperature trends are registered and can be traced on one or more monitors. The fact that the camera sees through smoke in case of a fire is an added bonus for any firefighting measures.

Intrinsic reliability
A reference unit ensures the measuring accuracy of the infrared camera and the accurate placement of the positioning device. In the course of each measuring cycle, the camera’s measurements are checked against the temperature on the reference unit. Any other necessary adjustment is undertaken anew, too. The calibration data is recorded, and the smooth operation of the infrared camera is monitored at the same time.

Operational reliability
To avoid detection errors and false alarms, the reference unit is subject to automated checks. It facilitates any necessary readjustment of the thermal calibration of the camera. A position test take place at regular intervals.

System architecture
In order to be able to scan the complete surface area of the waste, the infrared camera and reference unit are mounted in a suitable spot in the bunker. The camera signal is fed into a data analysis computer unit situated in the central electric control cabinet outside the bunker. Other external control systems such as fire extinguisher monitors, the central fire alarm system and the process control point are also connected to this central computer unit. A control panel and a TFT display are installed both in the crane operator cabin and in the central control room or CIE. In case of an alarm, visual and acoustic signals are given. 

Software
The ThermoObserver 1.1 early warning fire detection system software monitors all system components and the performance of the operating systems online. In order to achieve a high degree of software compatibility, it was developed especially for a standard operating system, Microsoft Windows. A Linux version will be available soon. In addition to the live infrared camera image, information concerning the status of the system and current temperature measurements are displayed on screen. Temperature changes and temperature peaks are registered in each of the different segments for those periods preceding an alarm.  A three-dimensional model of the bunker displays the position of the camera and scanned area, which simplifies the tagging of the live pictures - especially when thick smoke obscures the vision in case of a fire.

Fire alarm and fire tracking
The central data analysis computer unit monitors, evaluates and documents the predetermined alarm parameters and the trend alarm criteria.  If the alarm criteria are met in one of the bunker segments, the control element sets off an optical alarm signal to all connected screens and initiates a report to the CIE or process control room. A ring buffer containing the pictures of the preceding few hours is stored at this point in order to document the origin of the fire. The crane operator on duty will then manually operate the system in order to find the exact location of the fire source in the rapidly developing smoke. As a result, he will be able to remove the burning material, depositing it in the feed hopper.

Robust system
Within the overall system, the pan and tilt head and fitting are subjected to continuous and considerable wear, which makes them the parts most prone to technical failure. To address this problem, we have developed a robust pan and tilt head which is virtually maintenance-free. Electronically commutated motors, a precision gear, an optical positioning device, and the absence of any external electric cables assure the extremely long life span of our equipment.

System parameters

• Infrared camera system with high geometrical and thermal resolution capable of tracking small local hot spots early, i.e. while they are developing
• Infrared camera system with a sensitivity of 8 - 12 µm, in order to see through smoke and steam in case of fire
• online 24 hrs a day
• fully automatic central alarm
• documentation of alarm scenario to analyze fire source and development
• continuous, complete test of all system components combined with automatic signaling and documentation of possible system failure
• plain and clearly structured display of system information
• in case of fire alarm, easy option for manual operation by intuitive operator prompting
  

System failure
The so-called electronic Watchdog, detects faults in the early warning fire detection system or the system software. Should there be a system failure or parts of it malfunction, a clearly structured and classified notice shows up on all monitors.  All notices are recorded and archived. Within certain defined limits the system is fault tolerant.  Reports of disruptions are forwarded via relay to the central process control point. After entering the password the operator in charge can intervene immediately using the control unit, correct the problem or contact the Thermotemp service.