Since in industry fire chambers are now widely used to create all kinds of material, it is very important to monitor its stable operation. To meet this requirement, a flame detector must be used. Availability can be controlled by a specific set of sensors, the main purpose of which is to ensure the safe operation of various kinds of plants burning solid, liquid or gaseous fuels.
Product Description
In addition to the fact that flame control sensors are engaged in ensuring the safe operation of the furnace, they also take part in the ignition of a fire. This stage can be carried out in automatic or semi-automatic mode. During operation in the same mode, they make sure that the fuel burns out in compliance with all required conditions and protection. In other words, the continuous operation, reliability, and the safety of operation of furnace furnaces are completely dependent on the correct and trouble-free operation of flame control sensors.
Control methods
Today, a variety of sensors allows the use of various monitoring methods. For example, to control the process of burning fuel in a liquid or gaseous state, methods of direct and indirect control can be used. The first method can include such methods as ultrasonic or ionization. As for the second method, in this case, the flame relay sensors will control slightly different quantities - pressure, vacuum, etc. Based on the data received, the system will conclude whether the flame fits the specified criteria.
For example, in gas small heaters, as well as in domestic heating boilers, devices are used that are based on the photoelectric, ionization or thermometric flame control method.
Photoelectric method
Today, it is the photoelectric control method that is most often used. In this case, the flame control devices, in this case the photosensors, record the degree of visible and invisible radiation of the flame. In other words, the equipment captures optical properties.
As for the devices themselves, they respond to a change in the intensity of the incoming light stream, which emits a flame. The flame control sensors, in this case the photosensors, will differ from each other in such a parameter as the wavelength received from the flame. It is very important to take this property into account when choosing a device, since the characteristic of the spectral type of flame is very different depending on what type of fuel is burned in the furnace. During fuel combustion, there are three spectra in which radiation is formed - it is infrared, ultraviolet and visible. The wavelength can be from 0.8 to 800 microns, if we talk about infrared radiation. The visible wave can be from 0.4 to 0.8 microns. As for ultraviolet radiation, in this case the wave can have a length of 0.28 - 0.04 microns. Naturally, depending on the selected spectrum, the photosensors are also infrared, ultraviolet or luminosity sensors.
However, they have a serious drawback, which lies in the fact that the devices have too low a selectivity parameter. This is especially noticeable if the boiler has three or more burners. In this case, there is a great chance of an erroneous signal, which can lead to emergency consequences.
Ionization method
The second most popular is the ionization method. In this case, the basis of the method is the observation of the electrical properties of the flame. In this case, the flame control sensors are called ionization sensors, and the principle of their operation is based on the fact that they record the electrical characteristics of the flame.
This method has a rather strong advantage, which consists in the fact that the method has practically no inertia. In other words, if the flame goes out, the process of ionization of the fire disappears instantly, which allows the automatic system to immediately stop the gas supply to the burners.
Device reliability
Reliability is a basic requirement for these devices. In order to achieve maximum efficiency, it is necessary not only to choose the right equipment, but also to install it correctly. In this case, it is important not only to choose the correct installation method, but also the mounting location. Naturally, any type of sensors has its own advantages and disadvantages, however, if the installation location is incorrect, for example, the probability of a false signal increases significantly.
To summarize, we can say that for the maximum reliability of the system, as well as in order to minimize the number of boiler stops due to an erroneous signal, it is necessary to install several types of sensors that will use completely different methods of flame control. In this case, the reliability of the overall system will be quite high.
Combined device
The need for maximum reliability has led to the invention of the Archives combined flame detector, for example. The main difference from a conventional device is that the device uses two fundamentally different registration methods - ionization and optical.
As for the operation of the optical part, in this case it isolates and amplifies an alternating signal that characterizes the ongoing combustion process. During the burning of the burner, the flame is unstable and pulsating, data is recorded by the built-in photosensor. The recorded signal is transmitted to the microcontroller. The second is an ionization type sensor that can receive a signal only if there is a conductivity zone between the electrodes. This zone can exist only in the presence of flame.
Thus, it turns out that the device operates in two different ways to control the flame.
Marking sensors SL-90
Today, one of the rather versatile photosensors that can detect infrared radiation from a flame is the SL-90 flame monitoring sensor relay. This device has a microprocessor. A semiconductor infrared diode acts as the main working element, that is, a radiation receiver.
The elemental base of this equipment is selected so that the device can function normally at temperatures from –40 to +80 degrees Celsius. If you use a special cooling flange, then you can operate the sensor at temperatures up to +100 degrees Celsius.
As for the output signal of the SL-90-1E flame monitoring sensor, this is not only an LED indication, but also the contacts of a “dry” type relay . The maximum switching power of these contacts is 100 watts. The presence of these two output systems allows the use of a device of this type in almost any automatic type control system.
Burner control
Fairly common sensors for monitoring the flame of a burner are LAE 10, LFE10 devices. As for the first device, it is used in systems where liquid fuel is used. The second sensor is more versatile and can be used not only with liquid fuel, but also with gaseous.
Most often, both of these devices are used in systems such as dual burner control systems. It can be successfully used in systems of liquid fuel blower gas burners.
A distinctive feature of these devices is that they can be installed in any position, as well as attached directly to the burner itself, on the control panel or on the distribution panel. When installing these devices, it is very important to correctly lay the electrical cables so that the signal reaches the receiver without loss or distortion. To achieve this, you need to lay the cables from this system separately from other electrical lines. You must also use a separate cable for these monitoring sensors.