True innovation in optical flame detection

Introduction

According to some ‘innovation’ is a new idea, method, or product, all of which seems to apply to the FlameSpec flame detector product family from Fire and Gas Detection Technologies, inc. (FGD). True innovation is therefore an accurate or honest assessment of the new idea, method, or product. At FGD, we are committed to responding to the market requirements for improved performance and more reliable flame and gas detection products.

Fires are known to emit electromagnetic radiation in the infrared (IR), visible light and ultraviolet (UV) wavelengths depending on the fuel source. Flame detectors utilising sensors matched to the respective spectral bands measure the emitted radiant energy to determine if a flame is real.

Flame detector designers have long understood that the ‘perfect’ detector must achieve an exact balance between positive flame detection and absolute false alarm rejection. Today we still use numerous sensors and detection technologies to optimise detector performance, but with new innovations the gap to the ‘perfect’ infrared flame detector is getting smaller. This article will focus on innovations in infrared flame detection.

Infrared flame detection

Infrared (IR) flame detection technology has been around for several decades and has undergone significant advancements and improvements via the use of better optical filters and sensors. The main objective of IR flame detection is to detect and signal the presence of a fire. IR flame detectors do this by sensing the IR energy generated by combustion.

Today, triple IR flame detectors – or put more simply, detectors that use three infrared wavelengths –are the most common type of flame detectors available. The signal received by each sensor is analysed for several features that can be used to define fire like characteristics, these include:

Flickering frequency analysis
Threshold energy signal comparison
Mathematical ratios and correlations between various signals
Comparator techniques (and-gate techniques)
Correlation to memorized spectral analysis.

The FlameSpec IR3 product family employs several of the above features to enhance reliability and false alarm immunity. This combined with onboard datalogging has allowed FGD to continuously innovate. It is worth noting that there are several advantages to using IR flame detection technology, including:

Reliability: IR flame detectors are highly reliable and are capable of detecting fires quickly and accurately. They are also less susceptible to false alarms caused by other sources of IR energy, such as sunlight or incandescent lights.
Sensitivity: IR flame detectors are extremely sensitive and are capable of detecting fires even in difficult conditions, such as smoke, dust and fog.
Easy installation: IR flame detectors are easy to install and can be integrated into existing fire protection systems. They can also be connected to other fire protection systems, such as sprinklers or fire suppression systems, for added protection.
Cost-effective: IR flame detectors are relatively cost-effective and are a good investment for buildings and industrial facilities that are needed to protect against fire.

All technologies have limitations, and it’s the true innovations from FGD that address many of the perceived limitations of infrared flame detection. For example:

IR3 detectors false alarms to combustion gases from exhaust systems.
Special fires – IR3 cannot detect hydrogen, ammonia, or silane fires.
IR3 flame detectors are slow to respond.

True innovations – exhaust emissions

IR flame detectors are sensitive to most hydrocarbon fires (liquids, gases and solids). They do this by monitoring for the presence of hydrocarbon fires by measuring the amount of hot CO₂ in the device’s field of view. Additional sensors are used to cover different, adjacent, specially selected spectral bands, where black body emitters and background radiation may interfere.

The FlameSpec IR3 family not only monitors spectral characteristics but they record the data too, in some ways the devices act as mini-spectrum analysers. The data captured has allowed the FGD development team to establish an even deeper understanding of flame-like characteristics. Some FlameSpec IR3 models can, for example, internally decide what type of fire they are seeing, whether it be a dirty/smoky fire like diesel or aviation fuel or very clean burning flames like methane or methanol.

This innovation has allowed FGD to develop a unit that does not false alarm to the hot gaseous emissions of exhausts, which is a common problem for competing IR3 detectors. In some aircraft hangar applications aircraft may pass by a flame detector meaning the emission from the engine is visible for only a few seconds. Some competing flame detectors therefore simply employ a time delay that is longer than the period the ‘false alarm source’ might be present. FlameSpec CO2L does not do this, the detector specifically monitors for key fire-like characteristics that are produced by heavy hydrocarbon fuel fires. The FlameSpec CO2L innovation helps reduce false alarms in applications where exhaust gases may exist. Some examples include hangers for fixed wing aircraft and helicopters, helidecks, where engine downdraft can be an issue, road truck loading and where dumper trucks are used in tipping floor applications. The FlameSpec CO2L-HD configuration combines superior false-alarm immunity, outstanding speeds of detection and a HD CCTV capability that offers a live video feed with real-time incident status to operators who can make informed decisions and direct responders accordingly.

True innovations – special fires

Fires from fuels such as ammonia, hydrogen and silane do not emit significant amounts of IR in the spectral range used for hydrocarbon flame detection. This is because these fuels do not contain carbon atoms and so, carbon dioxide cannot be produced from these fires.

Alterative IR spectral wavelengths are needed to detect these fires. Some manufacturers do claim to have detection capability to these fuels, but these devices have proven unreliable, particularly in outdoor environments where sunlight can be a source of false alarm. The innovative FlameSpec IR3 platform with its unique combination of optomechanical design and filter selection, coupled with extensive testing, has allowed these, the most challenging of fires, to be detected indoors or outside.

The innovations for special fires don’t stop there. Hydrogen flames are invisible to the naked eye in bright sunlight. The absence of a visible flame poses a risk to plant operators who may need to verify the presence of a fire before acting. The FlameSpec family uniquely offers an IR3 detector with an embedded near-infrared camera. The FlameSpec IR3-H2-HD can clearly show moving hydrogen flames and explosions, at 30m, even in bright sunlight. This innovation allows operators to direct site personnel more safely around a facility. This device also records fire events for up to four minutes, this valuable information can be used for post incident investigation.

[Image of IR3-H2-HD]

IR3 flame detectors are slow to respond

Another limitation levelled at infrared flame detectors is that they are slow. Whilst it is true that IR3 flame detectors are very sophisticated, there has been significant improvement in sensor quality and processing speeds. Today IR3 flame detectors can alarm in as little as 40 milliseconds to an explosion at short distances, all whilst maintaining good false-alarm immunity. Another innovation from FGD saw the introduction of the FlameSpec X5 product family. Covering both IR3 and IR3-H2 product families the X5 meets the challenging response needs of NFPA 33.

NFPA 33 defines a list of requirements for Spray Application Using Flammable or Combustible Materials. The 2018 Edition, section 9.9.1, specifically requires ‘automated liquid electrostatic spray application equipment, both listed and unlisted, shall be further protected by listed optical flame detection, installed, and supervised in accordance with NFPA 72. The optical flame detection shall, in event of ignition, react to the presence of flame within one-half (0.5) second.’

All FlameSpec X5 models meet this requirement, with the response data for the FLS-IR3 given below. Please note the suffix 5 denotes this performance capability verified by Factory Mutual (FM).

Fuel	Size	Sensitivity	Range ft (m)	Response (s)
N-Heptane	1 x 1 ft	Medium	100 (30)	0.2
LPG	32-in Plume	Medium	100 (30)	0.4
Methanol	1 x 1 ft	Medium	59 (18)	0.3
N-Heptane	1 x 1 ft	Low	50 (15)	0.2
LPG	32-in Plume	Low	50 (15)	0.4
Methanol	1 x 1 ft	Low	30 (9)	0.3
N-Heptane	1 x 1 ft	Very Low	25 (7.5)	0.2
LPG	32-in Plume	Very Low	25 (7.5)	0.3
Methanol	1 x 1 ft	Very Low	15 (4.5)	0.4

Furthermore, section 15.5.10 defines the protection needs for Automated Powder Application Equipment. In this section, it is stated that ‘automated powder application equipment, both listed and unlisted, shall be further protected by listed optical flame detection, installed and supervised in accordance with NFPA 72. The optical flame detection shall, in the event of ignition, react to the presence of flame within one-half (0.5) second.’

Although the requirement for a sub-half-second speed of response is well documented by NFPA 33, speed of response is also a concern in other applications like aerosol filling stations and printing presses, conveyors and tunnels.

Summary

The development of IR flame detection technology has come a long way since its main adoption in the 1980s. From being bulky and unreliable, IR flame detectors today can be sophisticated mini-spectrum analysers with data logging and video recording. It is clear that IR flame detection has undergone significant advancements and improvements, and the pace of innovation has recently been accelerated by FGD. The FGD development team has been at the very forefront of flame detector innovations and they continue to push innovations to even higher levels. Today IR flame detectors are highly reliable and fast, making them an essential component of fire-protection systems.

Applications that were once extremely challenging, like aircraft hangars and tanker loading racks have been conquered by FGD innovations like FlameSpec CO2L. Special fires, like hydrogen, ammonia and silane can now be detected reliably indoors or outside. All of this combined with enhanced speeds of response, when every second, and sometimes millisecond, counts. The FGD development team has pushed the frontiers with true innovations in optical flame detection. What comes next? Watch this space.