Blogs listed by tag: LEL

Molecular Property Spectrometer™ Flammable Gas Sensors

Developed by NevadaNano, Molecular Property Spectrometer™ (MPS™) sensors represent the next generation of flammable gas detectors. MPS™ can quickly detect over 15 characterised flammable gases at once. Until recently, anyone who needed to monitor flammable gases had to select either a traditional flammable gas detector containing a pellistor sensor calibrated for a specific gas, or containing an infra-red (IR) sensor which also varies in output according to the flammable gas being measured, and hence needs to be calibrated for each gas. While these remain beneficial solutions, they are not always ideal. For example, both sensor types require regular calibration and the catalytic pellistor sensors also need frequent bump testing to ensure they have not been damaged by contaminants (known as ‘sensor poisoning’ agents) or by harsh conditions. In some environments, sensors must frequently be changed, which is costly in terms of both money and downtime, or product availability. IR technology cannot detect hydrogen – which has no IR signature, and both IR and pellistor detectors sometimes incidentally detect other (i.e., non-calibrated) gases, giving inaccurate readings that may trigger false alarms or concern operators.  

Building on over 50 years of gas expertise, Crowcon is pioneering advanced MPS™ sensor technology that detects and accurately identifies over 15 different flammable gases in one device. Now available in Crowcon’s flagship Xgard Bright fixed detector and portable detectors Gasman and T4x. 

Benefits of Molecular Property Spectrometer™ Flammable Gas Sensors 

The MPS™ sensor delivers key features that provide real world tangible benefits to operator and hence workers. These include:  

No calibration 

When implementing a system containing a fixed head detector, it is common practice to service on a recommended schedule defined by manufacturer. This entails ongoing regular costs as well potentially disrupting production or process in order service or even gain access to detector or multiple detectors. There may also be a risk to personnel when detectors are mounted in particularly hazardous environments. Interaction with an MPS sensor is less stringent because there are no unrevealed failure modes, provided air is present. It would be wrong to say there is no calibration requirement. One factory calibration, followed by a gas test when commissioning is sufficient, because there is an internal automated calibration being performed every 2 seconds throughout the working life of the sensor. What is really meant is – no customer calibration.  

Multi species gas – ‘True LEL’™ 

Many industries and applications use or have as a by-product multiple gases within the same environment. This can be challenging for traditional sensor technology which can detect only a single gas that they were calibrated for at the correct level and can result in inaccurate reading and even false alarms which can halt process or production if another flammable gas type is present. The lack of response or over response frequently faced in multi gas environments can be frustrating and counterproductive compromising safety of best user practices. The MPS™ sensor can accurately detect multiple gases at once and instantly identify gas type. Additionally, the MPS™ sensor has a on board environmental compensation and does not require an externally applied correctional factor. Inaccurate readings and false alarms are a thing of the past. 

No sensor poisoning 

In certain environments traditional sensor types can be under risk of poisoning. Extreme pressure, temperature, and humidity all have the potential to damage sensors whist environmental toxins and contaminants can ‘poison’ sensors, leading to severely compromised performance. Detectors in environments where poisons or inhibitors may be encountered, regular and frequent testing is the only way to ensure that performance is not being degraded. Sensor failure due to poisoning can be a costly experience. The technology in the MPS™ sensor is not affected by contaminates in the environment. Processes that have contaminates now have access to a solution that operates reliably with fail safe design to alert operator to offer a peace of mind for personnel and assets located in hazardous environment. Additionally, the MPS sensor is not harmed by elevated flammable gas concentrations, which may cause cracking in conventional catalytic sensor types for example. The MPS sensor carries on working.  

Hydrogen (H2) 

The usage of Hydrogen in industrial processes is increasing as the focus to find a cleaner alternative to natural gas usage. Detection of Hydrogen is currently restricted to pellistor, metal oxide semiconductor, electrochemical and less accurate thermal conductivity sensor technology due to Infra-Red sensors inability to detect Hydrogen. When faced with challenges highlighted above in poisoning or false alarms, the current solution can leave operator with frequent bump testing and servicing in addition to false alarm challenges. The MPS™ sensor provides a far better solution for Hydrogen detection, removing the challenges faced with traditional sensor technology. A long-life, relatively fast responding hydrogen sensor that does not require calibration throughout the life cycle of the sensor, without the risk of poisoning or false alarms, can significantly save on total cost of ownership and reduces interaction with unit resulting in peace of mind and reduced risk for operators leveraging MPS™ technology. All of this is possible thanks to MPS™ technology, which is the biggest breakthrough in gas detection for several decades.  

How does the Molecular Property Spectrometer™ Flammable Gas Sensor work 

A micro-electromechanical system (MEMS) transducer—comprising an inert, micrometer-scale membrane with an embedded heater and thermometer—measures changes in the thermal properties of the air and gases in its proximity. Multiple measurements, akin to a thermal “spectrum,” as well as environmental data are processed to classify the type and concentration of flammable gas(es) present, including gas mixtures. This is called  TrueLEL™. 

  1. Gas rapidly defuses through the sensor’s mesh screen and into the sensor chamber, entering the MEMS sensor module.​ 
  2. The joule heater rapidly heats the hot plate.​ 
  3. Real-time environmental conditions (temperature, pressure and humidity) are measured by the integrated environmental sensor.  
  4. The energy required to heat the sample is precisely measured using a resistance thermometer.​ 
  5. The gas level, corrected for gas category and environmental  conditions, is calculated and output to the gas detector. 

MPS in our Products 

Xgard Bright

Many industries and applications use or have as a by-product multiple gases within the same environment. This can be challenging for traditional sensor technology which can detect only a single gas that they were calibrated for at the correct level and can result in inaccurate reading. 

Xgard Bright with MPS™ sensor technology provides a ‘TrueLEL™’ reading for all flammable gases in any multi species environment without requiring calibration or scheduled maintenance over its 5-year+ lifecycle, reducing interruptions to your operations and increases up-time. This in turn reduces the interaction with the detector resulting in a lower total cost of ownership over the sensor life cycle and reduced risk to personnel and production output to complete regular maintenance. Xgard Bright MPS™ is tailor-made for Hydrogen detection, with the MPS™ sensor, only one device is needed saving space without compromising on safety. 

Gasman

Our MPS™ sensor technology has been designed for today’s multi-gas environments, resists contamination and prevents sensor poisoning. Give your teams peace of mind with a purpose-built device in any environment. The MPS technology in our portable gas monitors detects hydrogen and common hydrocarbons automatically in one sensor. Our reliable and dependable Gasman with industry leading sensor technology that your applications demand.

Gasman MPS™ provides a ‘TrueLEL™’ reading for all flammable gases in any multi species environment without requiring calibration or scheduled maintenance over its 5-year+ lifecycle, reducing interruptions to your operations and increases up-time. Being poison resistant and with battery life doubled, operators are more likely to never be without a device. Gasman MPS™ is ATEX Zone 0 approved enabling operators to enter an area in which an explosive gas atmosphere is present continuously or for long periods without fear their Gasman will ignite their environment. 

T4x

T4xAs the industry is continuously demanding improvements in safety, reduced environmental impact, and lower cost of ownership; our reliable and dependable portable T4x gas monitor meets those needs with its industry-leading sensor technologies. It is specifically designed to meet the demands of your applications. 

T4x helps operations teams focus on more value adding tasks by reducing the number of sensor replacements by 75% and increasing sensor reliability.    

Through ensuring compliance across site T4x helps health and safety managers by eliminating the need to ensure each device is calibrated for the relevant flammable gas as it accurately detects over 15 at once. Being poison resistant and with battery life doubled, operators are more likely to never be without a device.​ T4x reduces the 5-year total cost of ownership by over 25% and saves 12g of lead per detector which makes it much easier to recycle at the end of its life, and better for the planet​. 

For more on Crowcon, visit https://www.crowcon.com or for more on MPS™ visit https://www.crowcon.com/mpsinfixed/

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Gas-Pro TK: Dual readings of %LEL and %Vol

Gas-Pro TK (re-branded from Tank-Pro) dual range portable monitor measures the concentration of flammable gas in inerted tanks. Available for methane, butane and propane, Gas-Pro TK uses a dual IR flammable gas sensor – the best technology for this specialist environment. Gas-Pro TK dual IR features auto-range switching between %vol. and %LEL measurement, to ensure operation at the correct measurement range. This technology isn’t damaged by high hydrocarbon concentrations and does not need oxygen concentrations to work, as are the limiting factors of catalytic bead/ pellistors in such environments. 

What problem is Gas-Pro TK specifically designed to overcome? 

When you wish to enter a fuel storage tank for inspection or maintenance, you may start with it full of flammable gas. You can’t just start pumping air in to displace the flammable gas because at some point in the transition from only fuel present to only air present, there would be an explosive mixture of fuel and air. Instead, you must pump in an inert gas, usually nitrogen to displace the fuel without introducing oxygen. The transition from 100% flammable gas and 0% volume nitrogen, to 0% volume flammable gas and 100% nitrogen enables a safe transition from 100% nitrogen to air. Using this two-step process enables a safe transition from fuel to air without risking an explosion. 

During this process there is no air or oxygen present, so catalytic bead / pellistor sensors will not work properly and will also be poisoned by the high levels of flammable gas. The dual range IR sensor used by Gas-Pro TK does not require any air or oxygen to function, so it is ideal to monitor the whole of the process, from %volume to %LEL concentrations, while also monitoring oxygen levels in the same environment. 

What is LEL? 

The Lower Explosive Limit (LEL) is the lowest concentration of a gas or vapour that will burn in air. Readings are a percentage of that, with 100%LEL the minimum amount of gas needed to combust. LEL varies from gas to gas, but for most flammable gases it is less than 5% by volume. This means that it takes a relatively low concentration of gas or vapour to produce a high risk of explosion.
Three things must be present for an explosion to occur: combustible gas (the fuel), air and a source of ignition (as shown in the diagram). In addition, the fuel must be present at the right concentration, between the Lower Explosive Limit (LEL), below which the gas/air mixture is too lean to burn, and the Upper Explosive Limit (UEL), above which the mixture is too rich and there is not enough of a supply of oxygen to sustain a flame. 

Safety procedures are generally concerned with detecting flammable gas well before it reaches an explosive concentration, so gas detection systems and portable monitors are designed to initiate alarms before gases or vapours reach the Lower Explosive Limit. Specific thresholds vary according to the application, but the first alarm is typically set at 20% LEL and a further alarm is commonly set to 40% LEL. LEL levels are defined in the following standards: ISO10156 (also referenced in EN50054, which has since been superseded) and IEC60079. 

What is %Volume? 

The percent by volume scale is used to give the concentration of one gas type in a mixture of gases as a percentage of the volume of gas present. It is just a different scale with, for example the methane lower explosive limit concentration is displayed at 4.4% volume instead of 100% LEL or 44000ppm, which are all equivalent. If there was 5% or more methane present in air, we would have a highly dangerous situation where any spark or hot surface could cause an explosion where air (specifically oxygen) is present. If there is 100%volume reading, it means that there is no other gas present in the gas mix. 

Gas-Pro TK 

Our Gas-Pro TK has been designed for use in specialist inerted tank environments to monitor levels of flammable gases and oxygen, as standard gas detectors will not work. In ‘Tank Check Mode’ Our Gas-Pro TK device is suitable for specialist application of monitoring inerted tank spaces during purging or gas freeing, as well as doubles as a regular personal gas safety monitor in normal operation. It enables users to monitor the gas mix in tanks carrying flammable gas during transport at sea (as it is marine approved) or on shore, such as oil tankers and oil storage terminals. At 340g, Gas-Pro TK is up to six times lighter than other monitors for this application; a boon if you have to carry it with you all day. 

In Tank Check mode, the Crowcon Gas-Pro TK, monitors concentrations of flammable gas and oxygen, checking that an unsafe mixture is not developing. The device auto-ranges, switching between %vol and %LEL as gas concentration demands, without manual intervention, and notifies the user as it happens. Gas-Pro TK has real-time oxygen concentrations from within the tank on its display, so users can track the oxygen levels, either for when the oxygen levels are low enough to safely load and store fuel, or high enough for safe tank entry during maintenance. 

The Gas-Pro TK is available calibrated to methane, propane or butane.  With IP65 and IP67 ingress protection, Gas-Pro TK meets the demands of most industrial environments. With optional MED certifications, it is a valuable tool for tank monitoring on-board vessels. The optional High H₂S Sensor addition allows users to analyse possible risk if gases vent during purging. With this option, users can monitor over the 0-100 or 0-1000ppm range. 

Please note: if the fuel in the tank is hydrogen or ammonia, a different gas detection technique is required – and you should contact Crowcon. 

For more information on our Gas-Pro TK visit our product page or get in contact with our team.

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Industry Overview: Battery Power

Batteries are effective at reducing power outages since they can also store excess traditional grid energy. The energy stored within batteries can be released whenever a large volume of power is needed, such as during a power failure at a data centre to prevent data being lost, or as a back-up power supply to a hospital or military application to ensure the continuity of vital services. Large scale batteries can also be used to plug short-term gaps in demand from the grid. These battery compositions can also be used in smaller sizes to power electric cars and may be further scaled down to power commercial products, such as phones, tablets, laptops, speakers and – of course – personal gas detectors.

Applications include battery storage, transportation and welding and can be segregated into four main categories: Chemical – e.g., ammonia, hydrogen, methanol and synthetic fuel, electrochemical – lead acid, lithium ion, Na-Cd, Na-ion, electrical – supercapacitors, superconductive magnetic storage and Mechanical – compressed air, pumped hydro, gravity.

Gas Hazards

Li-ion battery fires

A major concern arises when static electricity or a faulty charger damages the battery protection circuit. This damage can result in fusing the solid-state switches into an ON position, without the user knowing. A battery with a faulty protection circuit may function normally, however, may not provide protection from short circuit. A gas detection system can establish if there is a fault and may be used in a feedback loop to shut off power, seal the space and release an inert gas (such as nitrogen) into the area to prevent any fire or explosion.

Leakage of toxic gases prior to thermal runaway

Thermal runaway of lithium-metal and lithium-ion cells has resulted in several fires. With research showing that fires fuelled by flammable gases are vented from the batteries during thermal runaway. The electrolyte in a lithium-ion battery is flammable and generally contains lithium hexafluorophosphate (LiPF6) or other Li-salts containing fluorine. In the event of overheating, the electrolyte will evaporate and eventually be vented out from the battery cells. Researchers have found that commercial lithium-ion batteries can emit considerable amounts of hydrogen fluoride (HF) during a fire, and that emission rates vary for different types of battery and state of-charge (SOC) levels. Hydrogen fluoride can penetrate skin to affect deep skin tissue and even bone and blood. Even with minimal exposure, pain and symptoms may not present for several hours, by which time damage is extreme.

Hydrogen and explosion risk

With hydrogen fuel cells gaining popularity as alternatives to fossil fuel, it is important to be aware of the dangers of hydrogen. Like all fuels, hydrogen is highly flammable and if it leaks there is real risk of fire. Traditional lead acid batteries produce hydrogen when they are being charged. These batteries are normally charged together, sometimes in the same room or area, which can generate an explosion risk, especially if the room is not properly ventilated. Most hydrogen applications cannot use odorants for safety, as hydrogen disperses faster than odorants do. There are applicable safety standards for hydrogen fuelling stations, whereby appropriate protective gear is required for all workers. This includes personal detectors, capable of detecting ppm level hydrogen as well as %LEL level. The default alarm levels are set at 20% and 40% LEL which is 4% volume, but some applications may wish to have a custom PPM range and alarm levels to pick up hydrogen accumulations quickly.

To find out more on the dangers of gas hazards in battery power visit our industry page for more information.

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What’s so Important about my Monitors Measuring Range?

What is a Monitor Measuring Range?

Gas monitoring is usually measured in PPM range (parts per million), percentage volume or percentage of LEL (lower explosive limit) this enables Safety Managers, to ensure that their operators are not being exposed to any potentially harmful levels of gases or chemicals. Gas monitoring can be done remotely to ensure that the area is clean before a worker enters the area as well as monitoring gas through a permanently fixed device or body worn portable device to detect any potentially leaks or hazardous areas during the course of the working shift.  

Why are Gas Monitors essential and what are the Ranges of deficiencies or enrichments?

There are three main reasons why monitors are needed; it is essential to detect oxygen deficiencies or enrichment as too little oxygen can prevent the human body from functioning leading to the worker losing consciousness. Unless the oxygen level can be restored to a normal level the worker is at risk of potential death. An atmosphere is considered to be deficient when the concentration of O2 is less than 19.5%. Consequently, an environment that has too much oxygen in it is equally dangerous as this constitutes a greatly increased risk of fire and explosion, this is considered when the concentration level of O2 is over 23.5%. 

Monitors are required when Toxic Gases are present of which can cause considerable harm to the human body. Hydrogen Sulphide (H2S) is a classic example of this. H2S is given off by bacteria when it breaks down organic matter, due to this gas being heavier than air, it can displace air leading to potential harm to persons present and is also a broad-spectrum toxic poison.  

Additionally, gas monitors have the ability to detect flammable gases. Dangers that can be prevented through using a gas monitor are not only though inhaling but they are a potential hazard due to combustion. gas monitors with an LEL range sensor detects and alert against flammable gases.  

Why are they important and how do they work?

Measurement or Measuring Range is the total range that the device can measure in normal conditions. The term normal meaning no overpressure limits (OPL) and within maximum working pressure (MWP).  These values are usually found on the product website or specification datasheet. The measuring range can also be calculated by identifying the difference between the Upper Range Limit (URL) and the Lower Range Limit (LRL) of the device. When trying to determine the range of the detector it is not identifying the area of square footage or within a fixed radius of the detector but instead is identifying the yielding or diffusion of the area being monitored. The process happens as the sensors respond to the gases that penetrate through the monitor’s membranes. Therefore, the devices have the ability to detect gas that is in immediate contact with the monitor. This  highlights the significance of understanding the measuring range of gas detectors and highlight their importance for the safety of the workers present in these environments.   

Are there any products that are available?

Crowcon offer a range of portable monitors; The Gas-Pro portable multi gas detector offers detection of up to 5 gases in a compact and rugged solution. It has an easy-to-read top mount display making it easy to use and optimal for confined space gas detection. An optional internal pump, activated with the flow plate, takes the pain out of pre-entry testing and allows Gas-Pro to be worn either in pumped or diffusion modes. 

The T4 portable 4-in-1 gas detector provides effective protection against 4 common gas hazards: carbon monoxide, hydrogen sulphide, flammable gases and oxygen depletion. The T4 multi gas detector now comes with improved detection of pentane, hexane and other long chain hydrocarbons. Offering you compliance, robustness and low cost of ownership in a simple to use solution. T4 contains a wide range of powerful features to make everyday use easier and safer. 

The Gasman portable single gas detector is compact and lightweight yet is fully ruggedised for the toughest of industrial environments. Featuring simple single button operation, it has a large easy-to-read display of gas concentration, and audible, visual and vibrating alarms.  

Crowcon also offer a flexible range of fixed gas detection products that can detect flammable, toxic and oxygen gases, report their presence and activate alarms or associated equipment. We use a variety of measurement, protection and communications technologies and our fixed detectors have been proven in many arduous environments, including oil and gas exploration, water treatment, chemical plants and steel mills. These fixed gas detectors are used in many applications where reliability, dependability and lack of false alarms are instrumental to efficient and effective gas detection. These include within the automotive and aerospace manufacturing sectors, on scientific and research facilities and in high-utilisation medical, civil or commercial plants. 

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How Hydrogen is Helping the Gas and Steel Industries to Go Green

Green hydrogen, taken from both low carbon and renewable energy sources, can play a crucial role in taking a company – or a country – closer to carbon neutrality. Common applications in which green hydrogen can be used include:

  • Fuel cells for electric vehicles
  • As the hydrogen in pipeline gas blending
  • In ‘green steel’ refineries that burn hydrogen as a heat source rather than coal
  • In container ships powered by liquid ammonia that is made from hydrogen
  • In hydrogen-powered electricity turbines that can generate electricity at times of peak demand

This post will explore the use of hydrogen in pipeline gas blending and green steel refineries.

Injecting hydrogen into pipelines

Governments and utilities companies worldwide are exploring the possibilities of injecting hydrogen into their natural gas grids, to reduce fossil fuel consumption and limit emissions. Indeed, hydrogen injection into pipelines now features in the national hydrogen strategies of the EU, Australia and the UK, with the EU’s hydrogen strategy specifying the introduction of hydrogen into national gas grids by 2050.

From an environmental point of view, adding hydrogen to natural gas has the potential to significantly reduce greenhouse gas emissions, but to achieve that, the hydrogen must be produced from low-carbon energy sources and renewables. For example, hydrogen generated from electrolysis, bio-waste or fossil fuel sources that use carbon capture and storage (CCS).

In a similar way, countries aspiring to develop a green hydrogen economy can turn to grid injection to stimulate investment and develop new markets. In an effort to kick start its renewable hydrogen plan, Western Australia is planning to introduce at least 10% renewable hydrogen into its gas pipelines and networks, and to bring forward the state’s targets under its renewable hydrogen strategy from 2040 to 2030.

On a volumetric basis, hydrogen has a much lower energy density than natural gas, so end-users of a blended gas would require a higher volume of gas to achieve the same heating value as those using pure natural gas. Simply put, a 5% blending of hydrogen by volume does not directly translate into a 5% reduction in fossil fuel consumption.

Is there any safety risk in hydrogen blending in our gas supply? Let’s examine the risk:

  1. Hydrogen has lower LEL than natural gas, so there is a higher risk of generating a flammable atmosphere with blended gas mixtures.
  2. Hydrogen has lower ignition energy than natural gas and a broad flammable range (4% to 74% in air), so there is higher risk of explosion
  3. Hydrogen molecules are small and move quickly, so any blended gas leak will spread faster and wider than would be the case with natural gas.

In the UK, domestic and industrial heating accounts for half of the UK’s energy consumption and one third of its carbon emissions. Since 2019, the UK’s first project to inject hydrogen into the gas grid has been underway, with trials taking place at Keele University. The HyDeploy project aims to inject up to 20% hydrogen and blend it with the existing gas supply to heat residential blocks and campuses without changing the gas-fired appliances or piping. In this project, Crowcon gas detectors and flue gas analyser are being used to identify the impact of hydrogen blending in terms of gas leak detection. Crowcon’s Sprint Pro flue gas analyser is being used to assess for boiler efficiency.

Crowcon’s Sprint Pro is a professional grade flue gas analyser, with features tailored to meet the needs of the HVAC professional, a robust design, full selection of accessories and 5-year warranty. Read more about the Sprint Pro here.

Hydrogen in the steel industry

Traditional iron and steel production is considered one of the largest emitters of environmental pollutants, including greenhouse gases and fine dust. Steel making processes rely heavily on fossil fuels, with coal products accounting for 78% of these. It is thus not surprising that the steel industry emits around 10% of all global process- and energy-related CO2 emissions.

Hydrogen may be an alternative for steel companies seeking to drastically reduce their carbon emissions. Several steel makers in Germany and Korea are already cutting emissions through a hydrogen reduction steelmaking method that uses hydrogen, not coal, to make steel. Traditionally, a significant amount of hydrogen gas is produced in steel making as a by-product called coke gas. By passing that coke gas through a process called carbon capture and storage (CCS), steel plants can produce significant amount of blue hydrogen, which can then be used to control temperatures and prevent oxidation during steel production.

In addition, steel makers are producing steel products specifically for hydrogen. As part of its new vision of becoming a green hydrogen enterprise, Korean steelmaker POSCO has invested heavily to develop steel products for use in the production, transport, storage and utilisation of hydrogen.

With many flammable and toxic gas hazards being present in steel plants, it is important to understand the cross sensitivity of gases, because a false gas reading could prove fatal. For example, a blast furnace produces a great deal of hot, dusty, toxic and flammable gas consisting of carbon monoxide (CO) with some hydrogen. Gas detection manufacturers that have experience in these environments are well acquainted with the issue of hydrogen affecting electrochemical CO sensors, and thus provide hydrogen-filtered sensors as standard to steel facilities.

To learn more about cross sensitivity, please see our blog. Crowcon gas detectors are used in many steel facilities across the world, and you can find out more about Crowcon solutions in the steel industry here.

References:

  1. Injecting hydrogen in natural gas grids could provide steady demand the sector needs to develop (S&P Global Platts, 19 May 2020)
  2. Western Australia pumps $22m into hydrogen action plan (Power Engineering, 14 Sep 2020)
  3. Green Hydrogen in Natural Gas Pipelines: Decarbonization Solution or Pipe Dream? (Green Tech Media, 20 Nov 2020)
  4. Could hydrogen piggyback on natural gas infrastructure? (Network Online, 17 Mar 2016)
  5. Steel, Hydrogen and Renewables: Strange Bedfellows? Maybe Not… (Forbes.com, 15 May 2020)
  6. POSCO to Expand Hydrogen Production to 5 Mil. Tons by 2050 (Business Korea, 14 Dec 202 0)http://https://www.crowcon.com/wp-content/uploads/2020/07/shutterstock_607164341-scaled.jpg
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Pellistor sensors – how they work

Pellistor gas sensors (or catalytic bead gas sensors) have been the primary technology for detecting flammable gases since the ‘60s. Despite having discussed a number of issues relating to the detection of flammable gases and VOC, we have not yet looked at how pellistors work. To make up for this, we are including a video explanation, which we hope you will download and use as part of any training you are conducting

A pellistor is based on a Wheatstone bridge circuit, and includes two “beads”, both of which encase platinum coils.  One of the beads (the ‘active’ bead) is treated with a catalyst, which lowers the temperature at which the gas around it ignites. This bead becomes hot from the combustion, resulting in a temperature difference between this active and the other ‘reference’ bead.  This causes a difference in resistance, which is measured; the amount of gas present is directly proportional to it, so gas concentration as a percentage of its lower explosive limit (%LEL*) can be accurately determined.

The hot bead and electrical circuitry are contained in flameproof sensor housing, behind the sintered metal flame arrestor (or sinter) through which the gas passes. Confined within this sensor housing, which maintains an internal temperature of 500°C, controlled combustion can occur, isolated from the outside environment. In high gas concentrations, the combustion process can be incomplete, resulting in a layer of soot on the active bead. This will partially or completely impair performance. Care needs to be taken in environments where gas levels over 70% LEL may be encountered.

For more information about gas sensor technology for flammable gases, read our comparison article on pellistors vs Infrared gas sensor technology: Are silicone implants degrading your gas detection?.

*Lower Explosive Limit – Learn more

Click in the top right hand corner of the video, to access a file that can be downloaded.

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