Many industries operate in hazardous environments. From oil and gas mining, refineries, and utilities, to food production, shipping and construction, exposure to harmful gases is common, and there are many reasons for wanting to monitor colourless gases.
Not only are these gases invisible to the human eye – sometimes odourless and tasteless too – but they are also often found in volatile and inaccessible environments. The most common toxic gases in modern industrial workplaces include ammonia, methane, hydrogen sulphide, chlorine, carbon monoxide, and carbon dioxide.
There are two broad categories of gas detectors: point detectors and area detectors. Point gas detectors have a single detector location requiring the gas cloud to interact with the sensor. Point detector types include catalytic, electrochemical, solid state, and infrared, abbreviated IR.
An IR detector consists of one or more infrared sources, one or more infrared detectors, and precision optical filters (pictured) to separate the sample and reference wavelengths from the background light. It also requires a light path which is open to the atmosphere so that gas can diffuse into the light beam.
IR gas detectors compare the amount of light at a certain wavelength where hydrocarbon molecules absorb light (known as the sample) with light at a wavelength where no absorption occurs (known as the reference). Due to the dependence of the absorbency on the wavelength, different gas components can be distinguished using the absorption spectrum. When the light passes through a hydrocarbon gas, the intensity at the sample wavelength will drop, while the intensity at the reference wavelength will be unaffected. The ratio of the two signals is proportional to the gas concentration.
While catalytic, semiconductor, electrochemical sensors and FIDs (flame ionisation detectors) all require the target gas to be present in concentrations below the lower explosion limit, IR sensors can accurately measure gas concentrations of 0-100%. What’s more, IR sensors do not require oxygen or external gases to operate.
Umicore has extensive experience designing system-critical infrared filters that detect noxious, harmful, and corrosive gases in the atmosphere in the parts per billion. A good example of this would be readings performed in the region surrounding a leak when a gas leak is identified. The profile collected at the scene is then compared to existing details of harmful molecular agents, enabling quick and targeted clean-up and, better still, prevention of catastrophic consequences.
USES
Gas detection systems have been deployed extensively in the process industry to detect and mitigate gas releases and minimise their potential consequences. Most of the current applications trigger an alarm for the operator based on high readings from gas detectors. However, with the industry push to incorporate safety gas sensors into shutdown systems, the need to design, calibrate and commission these sensors correctly to minimise nuisance trips is increasing in importance.
Continuing advances in technology have also resulted in detectors that continuously monitor combustible gases and vapours within lower explosive limits and provide alarm indications. These can be deployed within oxygen-deficient or enriched areas, require little calibration, and are immune to sensor poison, contamination, or corrosion.
Real-time measurements provided by modern technologies can now be coupled with GPS and GIS, software and communication solutions can record, transfer, store and analyse the data supplied by a larger set of interconnected fixed and mobile detectors.
Like much of Umicore’s work, it remains vital that the technology is adapted to the application, and so increasingly it is working with clients at an early stage of sourcing and defining optimum solutions. Therefore, existing and new customers are turning to our prototype design service with increased regularity, as they look to push this highly specialised engineering and technology through their product portfolios and businesses.