Introduction to Flame / Fire

Fires are created by the combination of fuel, heat, and oxygen. Different gases and substances can constitute as fuel, such as combustible gases and dust. Fire in an industrial setting can pose a number of hazards for the facility, its personnel, and the neighboring communities. The release of flammable material may result in several scenarios, including a fireball, pool fire, flash fire, flare or jet fire, or an unconfined explosion.

Two inherent hazards associated with fire are smoke and thermal radiation. Smoke created from fire poses two types of danger: visibility may be obscured, and health hazards arise due to inhalation and eye irritation. Thermal radiation can damage property and generate burns on exposed skin.

However, fire can also be used as a tool for mitigating a hazardous chemical’s potential impact. Deliberate ignition of a hazardous gas can minimize damages and produce more suitable environments. This technique has been successfully used for many years at oil and gas well sites.

Every industry working with combustible and toxic gases needs to have an understanding of the impact of the many hazards associated with fire. Proper fire detection solutions can be used to enable better situational analysis and more informed decision making during a fire event.

Technologies for Flame / Fire Detection

Sierra Monitor’s high performance flame detector products are variations of the most commonly used type, the optical flame detector. Optical flame detectors are designed to perform in the harshest environmental conditions and connect directly to alarm control panels. We provide a full line of industrial flame detectors designed to meet the needs of fire and safety professionals. Our optical flame detection systems feature single, dual, and tri-spectrum designs to provide a wide range of capabilities.

Selecting the right flame detector for your application depends on several factors: the nature of the fire, the size of the area to be protected, environmental conditions, detector capabilities and limitations, and other concerns must be considered.

UV (Ultraviolet) Flame Detectors

UV (ultraviolet) flame detectors can detect open flames, fires, and explosions within 3 to 4 milliseconds, as these sources emit UV radiation at the instant of ignition. UV flame detectors identify radiation in wavelengths between approximately 180 and 260 nanometers, and are designed to ignore sources of natural, incidental background radiation such as sunlight. However, false alarms can sometimes be triggered by other sources, such as electrical arc welding and halogen or quartz lighting. Many UV flame detector models integrate a 2 to 3 second time delay to reduce false alarms.

UV flame detection systems can detect hydrocarbon-based fuel and gas fires, invisible hydrogen flames, and fires fed by both organic and inorganic sources. Because nearly every possible source of flame or fire radiates UV light, UV flame detectors are a good all-around choice.

Sierra Monitor’s UV flame detectors detect hydrocarbon-based fuel and gas fires, invisible hydrogen flames, and fires from hydrides, ammonia, silane, and other organic sources.

IR (Infrared) Flame Detectors

IR (infrared) flame detectors monitor the heat radiation generated by fire and open flames, with a response time of roughly 3 to 5 seconds. Working within the infrared spectral band, these flame detection systems have a sensitivity range between approximately 4.3 to 4.4 micrometers. This range covers the resonance frequency of Carbon Dioxide (CO2), which is generated in large amounts by the burning of hydrocarbon materials such as wood and fossil fuels. Hot CO2 gases from fires produce a peak in total radiation emission, as well as a specific spectral pattern in the infrared range, both of which are easily detectable by IR flame detectors.

Incidental background thermal radiation and nearby hot surfaces can sometimes trigger false alarms in infrared flame detection systems. Ambient CO2 in air filters, IR radiation from sunlight, and many other sources could cause false alarms. Special programming algorithms designed to recognize the flicker frequency of flames (from one to 20 Hz) are often implemented, thus reducing false alarms caused by heat radiation from hot machinery or other sources.

A variation of these devices, called triple IR (IR3) flame detectors, compares three specific infrared wavelength bands and their relative ratios. Typically, this includes one sensor which detects radiation in the 4.4 micrometer range, with the other two sensors reading reference bands above and below that level. This gives IR3 flame detection systems the ability to better distinguish between CO2-emitting flames and non-flame IR sources, providing far greater accuracy and minimizing false alarms.

Sierra Monitor’s IR flame detectors detect hydrocarbon and hydrogen flames, fires fed by hydrocarbon-based fuels, gas fires, and other similar sources of flame. Different IR models with the highest immunities to false alarms can detect even the smallest of fires at distances ranging up to 215 feet away.

UV & IR Flame Detectors

UV & IR (UV/IR) flame detectors compare threshold signals from ultraviolet and infrared spectrums. Signals from both sensors are analyzed for intensity, frequency, and duration; this helps these systems better recognize different types of flame signatures and leads to fewer false alarms. Simultaneous detection of radiant energy in both sensors will trigger the system's alarm. Response times can be as fast as 150 milliseconds, though a three second range is more typical.

Different models of UV & IR flame detectors put varying emphasis on one technology over the other. Most UV/IR flame detection systems operate on infrared wavelengths between 2.5 and 4.5 micrometers, and can detect radiant energy in the short wave range of both ultraviolet and infrared spectrums. These flame detectors can detect hydrocarbon-based fuel and gas fires, hydrogen and hydroxyl fires, hydrocarbon fires, metal fires, and inorganic fires. Detection ranges varies from model to model.

Sierra Monitor carries different UV/IR flame detectors suitable for different situations, such as an industrial setting or a manufacturing wet bench.