Guía de selección de detectores de llama: ultravioleta, Y, UV/IR e IR3

Flame detector selection comes down to four variables: the fire type, the environmental interference in the area, the coverage required, and the explosion rating the location demands. Work through those four and the sensor technology picks itself. This guide does exactly that, in the order a real project needs.

ultravioleta. Y. UV/IR. IR3. Four sensor families, one job, and the differences between them matter more than most spec sheets admit.

The guide covers how flame detectors work, compares the four sensor technologies, addresses the false alarm problem head-on, and walks through mounting, coverage, and certification. Each section ends where the next buying decision begins.

What a Flame Detector Does

How Flame Detectors Detect Fire

A flame detector watches the electromagnetic signature of a fire. Flames emit in characteristic bands, ultraviolet around 185 a 260 nm and infrared in the 4.3 µm carbon dioxide emission band, and a detector tuned to those bands flags a growing fire in seconds, well before a thermal device or a smoke detector would respond.

The core of the physics is flicker. A real flame pulses at a characteristic frequency, and modern detectors use that flicker signature to separate fire from steady infrared sources such as heaters and hot pipework. Static radiation, no matter how bright, does not pass the flicker test.

Flame Detectors vs Smoke Detectors

Smoke detectors protect people. Flame detectors protect assets and processes. A smoke detector needs combustion products to reach it, which takes time and requires the smoke to travel. A flame detector sees the fire at the source, across an open area, and keeps working outdoors and in high-airflow spaces where smoke never accumulates.

The two complement each other. Flame detection covers the process area; smoke detection covers the building envelope. A facility running hazardous processes typically needs both, and the design documents should say which zone each device owns.

Four Sensor Technologies Compared

ultravioleta (Ultraviolet)

UV sensors watch the 185 a 260 nm band, which sunlight barely reaches, so UV units are inherently resistant to solar false alarms. Response is fast. The weakness is that UV is absorbed by smoke, fog, and oil mist, and arc welding is a classic nuisance source. A UV detector mounted in a welding bay is a detector that will not stay quiet.

Y (Infrarrojo)

IR sensors operate in the infrared, typically around the 4.3 µm band where carbon dioxide from combustion emits strongly. They see through smoke and some haze that blinds UV, and they tolerate dirty optics better. The classic failure is the sun itself, which radiates strongly in the infrared; IR-only units depend on discrimination logic to avoid solar nuisance trips.

UV/IR Combination

A UV IR flame detector requires both signals before alarming, which suppresses most single-source false alarms. A welding arc or a hot surface alone produces only one signal and gets ignored. The trade-off is a requirement for line of sight to both signatures and a slightly reduced response to some fire scenarios. El GSS800B is Otywell’s UV/IR dual-spectrum unit: 6-second response, viewing angle up to 120 grados, flameproof Ex d IIC T6 Gb with IP66 protection, RS485 output, DC24V supply, wall or ceiling mounting, about one kilogram. It is the standard recommendation for covered process areas where welding is controlled and solar interference is real.

IR3 Multi-Spectrum

IR3 units use three infrared channels and compare ratios and flicker patterns across all three, which gives the strongest rejection of solar and heat-source interference while keeping sensitivity to real flames. They are the default choice for high-risk outdoor areas such as tank farms, loading racks, and LPG storage. El S600-ExIR3 is the triple-IR flameproof unit in the range, with sensing channels at 4.4, 5.0, y 3.8 µm, a 6-second response, a viewing angle up to 110 grados, Ex d IIC T6 Gb and IP66, RS485 plus relay output, and wall or ceiling installation.

False Alarms: The Real Cost of Getting This Wrong

What Causes False Alarms

Welding arcs are the number one nuisance source indoors. Outdoors it is sunlight glinting off moving equipment, and in some plants a process line running hot straight through the detector’s field of view. Lightning has tripped more than one UV head. Every technology rejects part of this list and gets fooled by the rest, so an audit of what actually sits in the room usually decides the sensor before any datasheet does.

Sun. Soldadura. Heaters. Whatever the room throws at the optics picks the sensor, and a site survey settles more arguments than a spec sheet.

The Cost of a False Alarm

A false alarm in a chemical plant is never just a beep. The suppression system dumps, or worse, the plant goes into full emergency shutdown, and production stops while a crew of engineers figures out whether anything is actually burning. One facility installed IR-only heads in a process hall with two overhead heaters inside the field of view. The first alarm came within a week. The second arrived an hour after restart. Each event cost the facility most of a production day, which is a fast way for a detection project to get its budget questioned in writing.

The fix took two days: re-aim the heads, swap to UV/IR, done. The heater stopped being a problem because UV/IR needs two signals and a heater only makes one. None of this makes IR a bad technology. It was the wrong room for it, and a site audit costs less than one suppression trip.

Mounting and Coverage

Line of Sight and Viewing Angle

Line of sight is the whole game. A flame detector sees what it sees, and pipework, vessel skirts, and structural steel quietly eat coverage that the datasheet says is there. Viewing angle cuts the other way: 90 degrees covers a small room, 120 degrees covers a bigger one, and neither figure means much until the coverage math is done in three dimensions, because floor-plan geometry lies.

Mounting Height and Distance

Most integrators design against NFPA 72, and its rules on placement, spacing, and response time carry over to flame detection even though the code was written with smoke devices in mind. The mounting trade-off is simple enough: higher mount, wider cone, longer path to the floor. And the rated range on the datasheet assumes a clean window, which is an assumption worth checking twice.

Response time gets treated as an afterthought until commissioning, when the numbers refuse to line up. A detector aimed at a wall of pipework will not meet the detection time on the design sheet, and nothing about that improves by pointing at it harder.

Field of View Planning

Practical field-of-view planning is a drawing exercise: hazard envelope on the plan, obstruction shadows marked, detectors placed so every high-risk surface is seen by at least one head, ideally two. Redundancy at the design stage is nearly free. Redundancy after commissioning is a crane call and a shutdown window. And optics cleaning has to be on the maintenance schedule from the start, because a coated window is a detector that sees nothing.

Explosion-Proof Ratings and Certifications

Ex d vs Ex ia

Flame detector hardware comes in two protection flavors. Ex d is flameproof: the enclosure is built to contain an internal explosion so nothing propagates to the atmosphere outside. Ex ia takes the opposite route, limiting the energy in the circuit so ignition is never possible in the first place. Both are certified, both work, and the right one depends on the zone and how the site is wired.

En la práctica, flame detectors in Zone 1 process areas end up flameproof more often than not. The optics, el sensor, and the heater in the head draw more power than an intrinsically safe circuit is happy to supply, and the housing is big enough to carry the weight anyway.

Reading the Certificate

Certificates are where the real spec lives. The document lists the equipment group, the gas or dust group, the temperature class, and the zones the unit is actually approved for, and every line item has to line up with the site classification. In the United States, OSHA 1910.307 is the reference for hazardous (classified) locations and what “approved for the location” means. Match those line items to the zone before the purchase order goes out, because after delivery is too late to argue.

IECEx and International Approvals

Internationally, el IECEx scheme is the one to look for: certification for explosive atmospheres that is recognized across borders, and every certificate sits in a public online database where it can be checked in about a minute. For equipment that has to move between regions, IECEx or ATEX approval gets past customs desks and client HSE reviews that a local-only certificate stalls at.

Special Cases: Hydrogen Flames and Image-Based Detection

Detecting Invisible Hydrogen Flames

Hydrogen is the special case that keeps detection engineers honest. The flame is nearly invisible in daylight, because hydrogen combustion emits mainly in the ultraviolet and in the water-vapor infrared bands. UV and UV/IR heads pick those up, which is why they are the standard answer for electrolyzer halls, hydrogen fueling stations, and battery rooms where the gas can collect. A conventional IR3 unit watches the 4.3 µm carbon dioxide band, which hydrogen barely touches, so a hydrogen facility that leans on IR3 is betting on physics that is not there.

Image-Based Flame Detectors

Image-based detection is the newcomer that earns its keep in big spaces. A visible-light or IR camera runs flame analysis algorithms on motion, shape, flicker, and the spectral signature of what it sees, and in some models the unit reports where in the frame the fire is. One camera can replace several point detectors in a large open hall, and plants that already run video surveillance get the capability almost for free. Otywell’s Image type flame detector is the camera option in the range, aimed at warehouses, turbine halls, and covered outdoor storage.

Frequently Asked Questions About Flame Detectors

What is the difference between UV, Y, UV/IR and IR3 flame detectors?

UV detectors watch the ultraviolet band and respond fast but can be blinded by smoke and tripped by welding. IR detectors watch the infrared CO2 band and see through smoke but struggle with solar radiation. UV/IR units require both signals, rejecting most single-source false alarms. IR3 units compare three infrared channels and offer the strongest outdoor false-alarm rejection. The trade-off across all four is sensitivity against immunity to interference.

Can a flame detector be used outdoors?

Sí, with the right technology and weather rating. IR3 and UV/IR units are the outdoor choices because their multi-signal logic rejects solar radiation. The housing rating matters as much as the sensor: IP66 or higher keeps rain, polvo, and washdowns out, and outdoor units should be checked for ice or coating build-up on the window during regular maintenance.

What is the response time of a flame detector?

Rated response times for flame detectors typically fall between one and ten seconds, depending on the technology and the fire type. Otywell’s GSS800B and S600-ExIR3 are both rated at six seconds. The response time stated on the datasheet assumes a clean window and a fire inside the rated viewing angle; both conditions are installation and maintenance responsibilities.

How can false alarms be prevented on a flame detection system?

Audit the interference sources before selecting the sensor, then again before aiming it. Welding areas point toward IR3 or UV/IR rather than bare UV or IR. Keep heaters, exhausts, and sunlight reflections out of the field of view, and put optics cleaning on a real schedule. A multi-spectrum detector that is aimed correctly will outperform a single-band detector that is aimed conveniently.

Do flame detectors need to be explosion-proof?

Only if the location is classified. In hazardous areas, the equipment must be approved for the zone, and for flame detectors that normally means flameproof (Ex d) or intrinsically safe (A partir de ahora) construction with the gas group and temperature class matching the site. Outside classified areas, industrial-rated housings are sufficient. The zone classification is the first question a supplier should ask, and a buyer should walk away from any quote that skips it.

Where This Leaves You

Flame detector selection is a four-step decision: identify the fire type, audit the interference, calculate the coverage, and match the certification to the zone. Skip a step and the system either misses fires or alarms on nothing, and both failure modes cost more than the engineering time to avoid them.

If a site is speccing a flame detection system, send the hazard details, fuel types, area layout, zone classification, and known interference sources, to inquiry@otywell-safety.com or through the pagina de contacto, and get a sensor recommendation that matches the environment rather than a brochure.