A flame detector is an important fire protection device that can prevent loss of life & valuable possessions. It identifies the actual visible flame and triggers responses based on its installation, which may include sounding an alarm, disabling a fuel line, or activating a fire suppression system.
Some detectors have sensors for UV and IR radiation. This enables them to detect a wide range of flames, including hydrogen, metal & hydrocarbon fires.
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Low False Alarm Rates
Getting fire detection right is crucial in the oil and gas industry. False alarms not only can cause evacuations and system shutdowns but also cost the company time and money for the replacement of materials and equipment that were lost to the fire. They can even lead to investigations by fire safety inspectors and a loss of production while the investigation is carried out.
To ensure that the systems and processes in your facility are protected to the maximum extent possible, you need a sensor with very low false alarm rates. These are the detectors that can be relied upon to detect actual flames without being triggered by other heat sources such as electrical welding or the sun, and that can be trusted not to trigger unneeded actions like opening doors or activating fire suppression systems.
For this reason, flame detectors have evolved to meet the demands of many industries, such as oil & gas (onshore and offshore), petrochemicals, and hazardous material handling and storage, to provide high levels of reliability, availability, and fire detection performance required in these challenging environments. Modern IR3 detectors can reliably detect hydrocarbon and hydrogen flames and remove most of the common false alarm spectra, such as sunlight, flashing lights, or vehicle headlights.
There are two main types of flame detectors: UV and IR. UV detectors work with wavelengths shorter than 300 nm and can be easily confused with other radiation with similar wavelengths, such as ultraviolet radiation emitted by lightning, arc welding, or even sunlight. In order to overcome this issue, UV detectors often include a delay function that delays the reaction to 3-4 seconds.
IR flame detectors work within the infrared spectrum and recognize that hot gases emit unique spectral patterns, which can be recognized by sensors tuned to detect these frequencies. The most reliable IR detectors on the market are known as triple IR and work by using three separate spectral sensing elements in ‘AND’ configuration that analyze the signals in different ranges, comparing their ratios and eliminating unneeded responses.
The specific technology used in a flame detector can vary, but the majority of these sensors have a wide field of view (FOV) that can detect most industrial process fires. This means that the flame detector’s mounting location can be placed fairly close to a fire, and the operating staff doesn’t need to worry about the device being easily de-sensitized by sunlight or other factors.
Many process plants handle a variety of flammable liquids and gases, so it can be difficult to keep track of every area where flammable material is present. Flame detectors can help keep an eye on the entire facility, helping to prevent uncontrolled releases of flammable materials into other areas or nearby populated areas.
Typically, flame detectors use UV, IR, or UV/IR technology to identify flames based on the wavelengths of light they emit. This makes them fast acting, able to respond to fire quickly by sounding an alarm, disabling a fuel line, or activating a fire control system.
However, flame detectors cannot detect smoke or heat, and they can also be affected by reflections of infrared radiation from a fire that can be mistaken for a false signal. To avoid this, the manufacturer of a flame detector may include an additional sensor like an ultraviolet or visible light detector to ensure that only actual fire signals are detected.
Infrared (IR) flame detectors utilize a YG1006 phototransistor to sense the infrared radiation emitted from a flame or other clear source of light. The sensor looks much like a regular NPN transistor, except it has a longer terminal that works as an emitter and a shorter terminal that works as a collector. When the sensor detects a flame, it changes its state, and current flows in between the emitter and collector terminals.
IR flame detectors can be susceptible to black-body radiation, which reduces the range of the IR sensor by making the IR sensor reflect more of the ambient light back toward the sensor. This is why some IR flame detectors are designed with an additional UV-C band sensor, which acts as an anti-black-body filter and helps increase the sensitivity of the detector.
Wide Detection Range
Flame detectors identify fires by responding to radiant emissions from a fire. They use infrared (IR) or ultraviolet (UV) sensors to detect the radiation and then send a signal to a fire alarm system to activate it. When a fire is detected, the alarm signals can be used to sound an alarm, deactivate the fuel line, or activate a fire suppression system. The detectors can also be programmed to perform other tasks like monitoring gas concentrations.
While many different types of flame detectors exist, the best pick depends on the particular application rather than the detection technology. To determine the proper choice, evaluate the hazard to be detected and the dimensions of the area to be protected. Make sure the detectors are listed or approved for use in hazardous or classified areas and that they’re suitable for the environment they will operate in; for example, check that they meet UL 3260, EN 54-10, and ULC/ORD-C386 standards.
The simplest and least expensive type of flame detector is an IR sensor that detects infrared radiation to discover certain predefined prototypes given off by hot gases. These sensors are highly susceptible to water vapor which reduces their effectiveness and requires the detectors to be mounted in open modules.
Another option is an IR/UV combination flame detector, which adds sensors for both UV and IR radiation to enhance the overall performance of the device and improve its immunity to false alarms. These detectors work well in open modules but are not appropriate for closed systems such as turbine enclosures or offshore platforms.
The most advanced flame detectors are multi-spectral IR sensors with the highest protection and detection range. They combine a number of individual infrared sensors to characterize flames using multiple spectral spans and thus provide greater accuracy than single-span detectors. This also helps them resist de-sensitization by water, steam, fog, and blackbody radiation. These are ideal for oil and gas facilities, gas compressor buildings, refineries, MDF factories, gas-fueled cooking appliances, aircraft hangars, and other industrial settings where multiple process fluids may be in use.
The flame detector installation involves the sensor’s placement to ensure it can see the flames. This requires the elimination of any obstructions that could interfere with detecting the flames, including beams, girders, and other environmental features. The positioning of the flame detector should also be optimized to maximize the viewing angle and detection range. This can be done by analyzing the dimensions of the area to be protected and considering how the flames are generated. Once the detector is positioned, the trimpot can be used to set the sensor sensitivity. This is accomplished by turning the knob clockwise to increase sensitivity and counterclockwise to reduce it. The power LED on the flame detector is activated when the sensor detects a flame and turns off when it does not notice one.
Another benefit of flame detectors is that they are less complicated to install than other fire protection devices, such as smoke and heat sensors. This makes them ideal for hazardous and/or classified areas where other systems cannot be installed. Additionally, using a flame detector can help minimize costly downtime for your facility or plant by alerting personnel to fires sooner, allowing them to take preventive measures to thwart a fire from occurring.
A multi-infrared flame detector is a type with the best false alarm immunity because it is designed to detect both IR and UV radiation. This helps to differentiate the presence of a flame from other sources, such as black-body radiation that is given off by hot objects in the environment.
However, this type of sensor can still be prone to false alarms from non-fire sources, such as lightning or sparks. This can result in system shutdowns or evacuations and may also lead to investigations by the company or local authorities having jurisdiction over the area. Fortunately, these false alarms can be mitigated by placing the detector in more appropriate locations, decreasing the sensor sensitivity, and/or increasing the delay setting.
Ultraviolet/infrared (UV/IR) flame detectors combine IR and UV radiation sensors and operate them separately, just like two individual infrared detectors. These detectors typically include circuitry and wiring to assist them in analyzing and evaluating both signals, which can dispel any false alarms that one signal or the other might provoke. This boosted immunity to fake alarms permits UV/IR flame detectors to be utilized in both indoor and outdoor applications.