Types and principles of common flame detectors

The flame detector performs real-time monitoring of the burning condition based on the combustion characteristics of the flame. Once the flame is ignited that does not meet normal standards or is extinguished, a signal is obtained using a certain method to ensure that the supply is terminated when the heating furnace fires. It is mainly composed of a flame detection camera and a flame detection Cpu. It is mainly used for detecting flame, ambient temperature, and standard air pressure in the cabin.

1. Intelligent digital display composite flame detector, red and ultraviolet composite flame detector, using an ultraviolet sensor with low sensitivity to sunlight and a narrow band infrared sensor with high signal-to-noise ratio, can ensure detection sensitivity and improve immunity to non fire disaster sources (light blindness).

The carefully selected sensors in the red and ultraviolet composite flame detector ensure high sensitivity to the emission spectrum frequency caused by the flame; The detector's ultraviolet sensor incorporates a sequential logic circuit to avoid false alarms caused by solar radiation sources. The detector of Xuzhou Jieneng Electric Power Equipment Co., Ltd. can detect nitrogen oxide compounds igniting flames, such as radon, methyl chemicals, and metal and inorganic compounds igniting flame fires. The detector analyzes the frequency, brightness, and duration of signals received by ultraviolet and infrared sensors. Any sensor that receives the flame transmission frequency band can cause a report. The detector can work in harsh environments such as high/ultra-low temperatures, high/low temperatures, and vibrations.

2. The infrared flame detector selects lead sulfide or cadmium sulfide photosensitive sensors as sensor components, with a spectrometer response range of 0.7-3.2 μ M. Infrared flame detectors are composed of cameras, mainframe boxes, and refrigeration equipment. The radiation and heat transfer formed in the ignition area of the combustion engine flame are transmitted to the camera through optical guidance, converted into electrical signals based on the photosensitive sensors in the camera, and then amplified by an amplifier. The flame signal is sent to the main box through shielded twisted pair cables, and is compared with a reference voltage (adjustable) based on a frequency response switch and an amplifier circuit.

Infrared induction flame detector: Used for flame detection of natural gas burners. This detector is only sensitive to the generated infrared induction. Suitable for flame detection of natural gas and compressed natural gas. In addition, it is particularly suitable for working conditions such as fuel oil, coal water slurry, and raw coal.

3. Ultraviolet flame detectors belong to non-contact flame detectors. Compared to infrared flame detectors and hydrolytic flame detectors, they can detect tinier flames and are more flexible.

The ultraviolet flame detector uses ultraviolet sensitive tubes as sensor components, with a spectral range of O.006~0.4 μ M. UV sensitive tubes are solid state monopulse components that emit an arbitrary single pulse whose frequency is directly proportional to the frequency of ultraviolet radiation. UV sensitive tubes use two electrical levels, usually with a large AC current to communicate. When the ultraviolet light radiated into the electrical stage is sufficiently strong, a "avalanche" surge current will occur between the electrical stages, and its frequency is related to the compressive strength of the ultraviolet light, reaching thousands of HZ. There is no single pulse when fighting a fire.

Ultraviolet flame detector: This type of flame detector is used for flame detection of natural gas, gasoline and diesel industrial burners. This detector is only sensitive to the generated ultraviolet light, and has no reaction to light and continuous high-temperature radiation sources in the furnace, with strong anti-interference ability.  The ultraviolet flame detector includes a conventional ZQ-102 ultraviolet flame detector and an explosion-proof ultraviolet flame detector (FZQ-102).

4. Visible flame detector The visible flame detector uses photodiodes as sensor components, with a spectrometer response range of 0.33 to 0.7? M middle. The visible flame detector consists of a camera, a main unit box, and refrigeration equipment. The visible light in the furnace flame passes through the lens at the top of the camera, passes through the light guide, reaches the camera compartment, and irradiates onto the photodiode.

The photodiode converts visible light signals into electrical flow signals, which are converted into operating voltage signals by most amplifiers. The voltage signal derived by most amplifiers is then converted into an electrical flow signal by a transmission amplifier. And then transmitted to the host box through shielded twisted pair. In the main box, the current signal is also converted into a working voltage signal. It means that the voltage signals of the flame are respectively sent to the frequency inspection distribution line, the compressive strength inspection line, and the fault test distribution line. The distribution line for compressive strength testing is equipped with two different limit values, namely, the upper limit value and the lower limit value. When the flame compressive strength exceeds the upper limit value, the compressive strength lamp lights up, indicating a fire; When the compressive strength is less than the lower limit value, the compressive strength light goes out, indicating that the fire is being extinguished.

The frequency inspection distribution line is used to inspect the flame flicker frequency in the furnace. It can correctly determine whether there is a flame in the furnace based on whether the flame flicker frequency is greater than or less than the set frequency. The fault test distribution line also has two limit values, which under normal conditions are maintained between the lower and lower limit values.  Once there is an abnormality in the signal input control circuit of the main box, such as the disconnection of the cable from the discharge tube to the main box, the above working voltage signal immediately shifts from the normal range, and a fault warning signal is sent out.

5. Hydrolyzed flame detectors are mainly used for flame detection of natural gas industrial burners. Reliable detection performance, capable of removing and cleaning carbon deposits, as well as the impact of wiring contact resistance. It is only relatively sensitive to flame, has no reaction to continuous high temperatures, and has strong anti-interference ability. It can prevent high temperatures and rain during use.