Low-cost flame monitoring system

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May 2005 Sensors & Transducers

Durag's low-cost flame monitoring system consists of a D-UG 110 or D-UG 120 control unit in combination with a D-LE 103 flame sensor. The system is designed for continuous operation and for 72h operation according to TRD 604. It is able to monitor flames of all burner types, fuels and combustion modes.

The flame sensor is available for different spectral ranges from UV to IR. UV flame sensors are mainly used for gas firings, whereas in the case of liquid and solid fuels, it is the high emission in the IR region that will be evaluated.

The flame sensor can be aligned optimally to the flame when a digital display (displaying the current flame intensity) is connected to the control unit. Further information such as minimum and maximum flame intensity are displayed, as well as a recommended setting for the response threshold. A built-in LED display provides the operator with all required information. In case of an internal error, the type of error is indicated by the appropriate blinking code of the LEDs.

After start-up the control unit performs a self-test that is periodically repeated during the operation. The threshold for the 'flame on' indication can be set in 10 steps to allow for adaptation to the intensity of different flames. For interference-free transmission through long lengths of cable, all flame sensors convert the flame signal into a strong pulse train of variable frequency, which is transmitted to the control unit where the pulse rate is counted.

An analog output signal informs the user on the stability of the burner flame. Changes to the flame structure lead to changes of the pulse frequency and are recognisable through the analog output of the control unit. This is important information for obtaining and preserving optimal operation conditions.

Ultraviolet flame sensors are available with a spectral range of either 196 to 260 nm, 190 to 520 nm or 280 to 410 nm depending on the model. All blue burning flames such as gas flames where their portion of visible light is low may be monitored by these flame sensors.

Infrared flame sensors have a spectral sensitivity of either 300-1100 nm or 780 to 1800 nm depending on the model. Flames where UV radiation is absorbed by dust, water vapour or other materials may be monitored in the infrared range.

All flame sensors have been tested according to EN 230 (oil) and EN 298 (gas) and they have been approved and certified by numerous independent test institutes. Durag is represented locally by OEN Enterprises.

For more information contact Mauritz van Niekerk, OEN Enterprises, 011 675 4447, mauritz@oenenterprises.co.za, www.oenenterprises.co.za

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Low-cost flame monitoring system

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