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Flame Detection

Optical | Ionisation | Flame Sensing Electrodes

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Types Of Burner Flame Detectors

Flame detectors range from simple ionisation probes designed to sit at the root of the flame, through to complex microprocessor solid state flame scanners that can be ‘tuned’ to select an individual flame from several visible flames.

The radiation emitted is determined by the fuel used. As a general rule-of-thumb, gaseous fuels produce UV radiation and liquid/solid fuels produce IR. However, most fuels produce a range of emissions across both the UV & IR spectrum meaning there is crossover when deciding on which type of flame detector to use.

Optical Flame Detector

UV flame detectors are specialized devices in industrial combustion systems that leverage ultraviolet (UV) radiation to detect and monitor flames. These essential safety tools not only enhance system efficiency but also ensure the secure operation of combustion processes.

Equipped with a UV-sensitive sensor, a UV flame detector is attuned to UV wavelengths emitted by a flame during combustion. This sophisticated technology captures the UV radiation, transforming it into an electrical signal. This data is then processed and scrutinized by control systems, providing valuable insights into the combustion process.

These detectors excel in accurately identifying the presence, stability, and characteristics of a combustion flame. They offer reliable detection capabilities even in challenging industrial conditions, such as areas with significant amounts of smoke, dust, or intense background lighting.

UV flame detectors are indispensable in industrial combustion systems like furnaces, boilers, and gas turbines. By promptly identifying irregularities such as flameouts or suboptimal combustion, these devices facilitate immediate intervention, reducing potential risks and optimizing operational performance.

Industrial Combustion Systems and IR Flame Detectors: Improving Safety and Efficiency

IR (infrared) flame detectors are essential safety devices in industrial combustion systems. They utilize infrared radiation, a by product of the combustion process, to detect and monitor flames, thus bolstering system safety and efficiency.

An IR flame detector features an infrared sensor, purposefully designed to detect the unique infrared wavelengths of combustion flames. As fuel burns and releases energy in the form of infrared radiation, the detector captures it and converts it into an electrical signal for further analysis.

These detectors distinguish between flames and other heat or infrared radiation sources by identifying unique flame signatures. This ensures accurate flame detection even in environments with high ambient temperatures or numerous heat sources.

IR flame detectors are crucial in monitoring flame presence and stability across various industrial applications, including furnaces, boilers, and incinerators. They furnish crucial information about flame status and characteristics, thereby promoting optimal combustion, preventing flameouts, and alerting operators to abnormal flame activity or potential hazards.

By detecting flame anomalies swiftly and providing real-time data to control systems, IR flame detectors enhance the safety and efficiency of industrial combustion processes. This contributes significantly to risk minimization and performance optimisation.

Ionisation Probes

The ionisation probe, also known as an ionisation rod or flame sensor, plays a crucial role in combustion systems by detecting the presence or absence of a flame. It is a vital component that ensures the safe and efficient operation of various heating and combustion processes.

What is an Ionisation probe?

Comprised of a conductive metal rod, typically constructed from stainless steel or a suitable material, the ionisation probe is strategically positioned within the combustion chamber or near the burner flame. Once the burner is ignited, the flame engulfs the ionisation probe.

When the flame interacts with the probe, it induces ionisation in the surrounding air molecules. This ionisation process causes the air particles to acquire an electric charge, resulting in the generation of ions. The conductive metal rod of the ionisation probe serves as an electrode, facilitating the flow of these ions and enabling the formation of a small electrical current.

The combustion system continuously monitors this electrical current to ascertain the presence or absence of the flame. If the flame becomes extinguished or goes undetected, the electrical current will decrease significantly or halt altogether. This abrupt change in current triggers built-in safety mechanisms or prompts the initiation of corrective actions to prevent hazardous conditions or unnecessary fuel wastage.

What is its purpose?

The primary purpose of the burner ionisation probe is to provide reliable and rapid flame detection, ensuring optimal performance and safeguarding against potential hazards. By swiftly detecting any flame-related issues, such as flame failure, the ionisation probe contributes to the overall safety and efficiency of the combustion system.

Thanks to its ability to detect flame presence accurately and promptly, the ionisation probe acts as a vital safeguard, preventing the release of unburned fuel into the environment or the accumulation of potentially explosive gases. It enables the combustion system to maintain stable and controlled combustion, minimizing the risk of accidents, inefficiencies, and environmental harm.

In summary, the ionisation probe is an indispensable component of combustion systems, serving as a critical safety feature. Through the principle of ionisation, it detects the presence or absence of a flame, allowing for timely corrective measures to ensure safe and efficient operation.

 

Maintaining Your Flame Safety System

Contamination of the detector’s lens with dust or oil also affects performance. This can be alleviated with the addition of Quartz lenses in front of the sensor or with compressed air being fired over the lens to keep it clear of contaminants. More regular servicing is also required in these environments.

Do I Need a Self Checking Flame Detector

Systems can be classed as either non-continuous or continuous operation. Non-continuous operation requires that the burner be switched off at least once every 24 hours to confirm the flame detector is able to detect both states i.e. flame in/flame out.

Some flame detectors, for example, a UV tube, may have a non-failsafe failure mode, meaning their operation needs to be verified periodically. Continuous operation can be achieved by using a device containing a mechanical shutter that allows the detector to self-check by simulation of a no flame condition.

More modern flame detectors use more sophisticated methods for self-checking. A characteristic of nearly all flames is that they flicker. This is a product of the fuel type, combustion process and mechanical design of the burner. Flicker frequency tends to increase with firing rate as a result of higher air velocity and fuel mixing at the burner head or nozzle. Flicker frequency varies along the flame path dropping off significantly towards the end of the flame. This characteristic can be used to ‘tune’ a flame detector to discriminate one flame from another in multi-burner systems or to discriminate the flame from other background radiation. These more intelligent flame detectors monitor the flicker and the self-check using software rather than mechanical operation.

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