gas detector is a device that detects the presence of gas in an area, often as part of a security system. This type of equipment is used to detect gas leaks or other emissions and can interact with the control system so that the process can be closed automatically. The gas detector can sound an alarm to the operator in the area where the leak occurred, giving them a chance to leave. This type of device is important because there are many gases that can harm organic life, such as humans or animals.
Gas detectors can be used to detect flammable, combustible and toxic gases, and oxygen depletion. This type of device is widely used in industry and can be found on site, such as on oil rigs, to monitor manufacturing processes and emerging technologies such as photovoltaics. They can be used in firefighting.
Gas leak detection is the process of identifying dangerous gas leaks by sensors. These sensors usually use audible alarms to alert people when harmful gases have been detected. Exposure to toxic gases can also occur in operations such as painting, fumigation, refueling, construction, excavation of contaminated soil, landfill operations, entering limited space, etc. Common sensors include flammable gas sensors, photoionization detectors, infrared point sensors, ultrasonic sensors, electrochemical gas sensors, and semiconductor sensors. Recently, infrared imaging sensors are being used. All these sensors are used for various applications and can be found in industrial plants, refineries, pharmaceutical manufacturing, fumigation facilities, pulp mills, aircraft and ship facilities, hazmat operations, wastewater treatment facilities, vehicles, indoor air. quality and home testing.
Video Gas detector
Histori
The method of gas leak detection is of concern after the harmful gas effects on human health are found. Before modern electronic sensors, early detection methods rely on a less precise detector. Through the nineteenth and early twentieth centuries, coal miners will carry walnuts to their mutual tunnels as early detection systems of life-threatening gases such as carbon dioxide, carbon monoxide and methane. Walnut, usually a very loud bird, will stop singing and eventually die if not expelled from these gases, indicating the miners to get out of the mine quickly.
The industry's first gas detector was a fire safety lamp (or Davy lamp) discovered by Sir Humphry Davy (from England) in 1815 to detect the presence of methane (firedamp) in an underground coal mine. The flame safety lamp consists of an oil flame adjusted to a certain height in fresh air. To prevent ignition with the flame of the lamp contained in a glass sleeve with a flame retardant mesh. The height of fire varies depending on the presence of methane (higher) or lack of oxygen (lower). To this day, in certain parts of the world's glowing safety lamps are still in service.
The modern era of gas detection began in 1926-1927 with the development of catalytic combustion sensor (LEL) by Dr.Oliver Johnson. Dr Johnson is an employee of Standard Oil Company in California (now Chevron), he began his research and development methods to detect combustible mixtures in the air to help prevent explosions in fuel storage tanks. A demonstration model was developed in 1926 and is denoted as Model A. The first "electric steam indicator" meter practically began production in 1927 with the launch of Model B.
The world's first gas detector company, Johnson-Williams Instruments (or J-W Instruments) was formed in 1928 in Palo Alto, CA by Dr. Oliver Johnston and Phil Williams. The J-W instrument is recognized as the first electronics company in Silicon Valley. Over the next 40 years, JW Instruments pioneered many of the "firsts" in the modern era of gas detection, including making smaller and more portable instruments, developing portable oxygen detectors and the first combined instrument that can detect flammable gases as well as oxygen.
Prior to the development of electronic household carbon monoxide detectors in the 1980s and 1990s, the presence of carbon monoxide was detected with chemical paper turning brown when exposed to gas. Since then, many technologies and electronic devices have been developed to detect, monitor, and warn leaks of various gases.
As the cost and performance of electronic gas sensors increases, they have been incorporated into a wider range of systems. Their use in cars initially for engine emission control, but now gas sensors can also be used to ensure passenger comfort and safety. The carbon dioxide sensor is being installed into the building as part of a demand-driven ventilation system. Advanced gas sensor systems are being researched for use in medical diagnostics, monitoring, and treatment systems, well beyond their initial use in operating rooms. Gas monitors and alarms for carbon monoxide and other harmful gases are increasingly available for use in offices and households, and are legally required in some jurisdictions.
Initially, detectors are produced to detect a single gas. Modern units can detect some toxic or flammable gas, or even combinations. Newer gas analyzers can break down component signals from complex scents to identify multiple gases simultaneously.
Maps Gas detector
Type
Gas detectors can be classified according to the operating mechanism (semiconductor, oxidation, catalytic, photoionization, infrared, etc.). Gas detectors are packaged into two main form factors: portable devices and fixed gas detectors.
Portable detectors are used to monitor the atmosphere around personnel and whether hand-held or worn on clothing or on a belt/harness. This gas detector is usually operated by battery. They send warnings through audible and visible signals, such as alarms and flashing lights, when the level of gas vapor hazard is detected.
Fixed-type gas detectors can be used to detect one or more types of gases. Fixed-type detectors are generally installed near the factory's processing area or control room, or areas to be protected, such as a residential bedroom. Generally, industrial sensors are mounted on lightweight fixed-type steel structures and cables connecting detectors to SCADA systems for continuous monitoring. Interlock trips can be activated for emergency situations.
Electrochemical
The electrochemical gas detector works by enabling the gas to diffuse through the porous membrane to the electrode in which it is oxidized or reduced chemically. The amount of current generated is determined by how much gas is oxidized to the electrode, indicating the gas concentration. Manufacturers can adjust the electrochemical gas detector by changing the porous barrier to allow detection of specific gas concentration ranges. Also, because the diffusion barrier is a physical/mechanical barrier, the detector tends to be more stable and reliable over the duration of the sensor and thus required less maintenance than other early detector technologies.
However, these sensors are subject to corrosive elements or chemical contamination and may last only 1-2 years before replacement is required. Electrochemical gas detectors are used in various environments such as refineries, gas turbines, chemical plants, underground gas storage facilities, and more.
The catalytic beads (pellistor)
The catalytic bead sensors are commonly used to measure flammable gases that present an explosion hazard when the concentration is between the lower border of the explosion (LEL) and the upper explosive limit (UEL). Active and reference beads containing platinum wire coils are located in the opposite arm of the Wheatstone bridge circuit and are electrically heated, up to several hundred degrees C. The active bead contains a catalyst which allows the oxidizable compound to oxidize, thus warming the bead further and altering electrical resistance. The resulting voltage difference between the active and passive beads is proportional to the concentration of all flammable gases and vapors present. The sample gas enters the sensor through sintered metal frit, which provides a barrier to prevent explosions when the instrument is brought into an atmosphere containing combustible gas. Pellistors basically measure all flammable gases, but they are more sensitive to smaller molecules that spread through sinter faster. The measured concentration range is usually from a few hundred ppm to several percent of volume. Such sensors are cheap and powerful, but require at least a few percent oxygen in the atmosphere to be tested and they can be poisoned or inhibited by compounds such as silicon, mineral acids, chlorinated organic compounds, and sulfur compounds.
Photoionization
The photoionization detector (PIDs) uses high-energy UV photons to ionize chemicals in sample gases. If the compound has ionisation energy beneath the lamp photon, the electrons will be removed, and the resulting current is proportional to the concentration of the compound. General lamp photon energy including 10.0 eV, 10.6 eV and 11.7 eV; the standard 10.6 eV lamp lasts for years, while the 11.7 eV lamp usually lasts only for a few months and is used only if no other options are available. Various compounds can be detected at levels ranging from a few ppb to several thousand ppm. Classes of detectable compounds in order to decrease the sensitivity include: aromatics and alkyl iodides; olefins, sulfur compounds, amines, ketones, ethers, alkyl bromides and silicate esters; organic esters, alcohols, aldehydes and alkanes; H2S, NH3, PH3 and organic acids. There is no response to standard components of air or mineral acids. The main advantage of PIDs is their excellent sensitivity and simplicity of use; The main limitation is that the measurement is not specific-compound. Recently PIDs with pre-filter tubes have been introduced that increase the specificity for compounds such as benzene or butadiene. Handheld, hand-held and miniature PIDs are widely used for industrial hygiene, hazmat, and environmental monitoring.
Infrared point
The infrared point sensor (IR) uses radiation passing through a known gas volume; the energy from the sensor beam is absorbed at a certain wavelength, depending on the specific gas properties. For example, carbon monoxide absorbs a wavelength of about 4.2-4.5 m. The energy in this wavelength is compared to the wavelength beyond the absorption range; the energy difference between these two wavelengths is proportional to the existing gas concentration.
This type of sensor is advantageous because it does not have to be placed into the gas to detect and can be used for remote sensing. Infrared point sensors can be used to detect hydrocarbons and other infrared active gases such as water vapor and carbon dioxide. IR sensors are commonly found in wastewater treatment facilities, refineries, gas turbines, chemical plants, and other facilities where flammable gas and possible explosions are present. Remote sensing capability allows large volume of space to be monitored.
Engine emissions are another area where IR sensors are being investigated. The sensor will detect high levels of carbon monoxide or other abnormal gases in the vehicle's exhaust and even be integrated with the vehicle's electronic system to notify the driver.
Infrared imaging
The infrared image sensor includes both active and passive systems. For active sensing, IR imaging sensors typically scan lasers across the field of view of the scene and search for backscattered light at absorbing wavelengths of specific gas targets. The passive IR imaging sensor measures the spectral changes in each pixel in the image and looks for a specific spectral signature that indicates the presence of the target gas. The types of compounds that can be imaged are identical to those detectable with the infrared point detector, but the images can help identify the gas source.
Semiconductor
Semiconductor sensors detect gas by chemical reactions that occur when the gas is in direct contact with the sensor. Tin dioxide is the most common material used in semiconductor sensors, and the electrical resistance in the sensor decreases when in contact with the monitored gas. Tin dioxide resistance is usually about 50 k? in the air but can drop to about 3.5 k? in the presence of 1% methane. This resistance change is used to calculate the gas concentration. Semiconductor sensors are commonly used to detect hydrogen, oxygen, alcohol vapor, and harmful gases such as carbon monoxide. One of the most common uses for semiconductor sensors is the carbon monoxide sensor. They are also used in breathalyzer. Because the sensor must come into contact with the gas to detect it, the semiconductor sensor works at a smaller distance than the infrared point or ultrasonic detector.
Ultrasonic
The ultrasonic gas leakage detector is not a gas detector per se. They detect acoustic emissions created when depressed gas expands in a low pressure area through a small hole (leak). They use acoustic sensors to detect changes in background noise of the environment. Since most high-pressure gas leaks produce sound in the ultrasonic range from 25 kHz to 10 MHz, sensors can easily differentiate these frequencies from background acoustic noise occurring in the 20 Hz to 20 kHz range. The ultrasonic gas leak detector then generates an alarm when there is an ultrasonic deviation from normal background noise conditions. The ultrasonic gas leakage detector can not measure the gas concentration, but the device is capable of determining the escape gas leakage rate because the ultrasonic sound level depends on the gas pressure and leakage size.
Ultrasonic gas detectors are primarily used for remote sensing in outdoor environments where weather conditions can easily eliminate escaping gas before it is possible to reach a leak detector that requires contact with the gas to detect and sound an alarm. These detectors are commonly found in offshore and onshore oil/gas platforms, gas compressors and measuring stations, gas turbine power plants, and other facilities that accommodate many outer pipelines.
Holographic
The holographic gas sensor uses light reflections to detect changes in the matrix of polymer films containing holograms. Because holograms reflect light at certain wavelengths, their composition changes can produce colorful reflections that indicate the presence of gas molecules. However, holographic sensors require lighting sources such as white or laser light, and observers or CCD detectors.
Calibration
All gas detectors must be calibrated on schedule. Of the two gas form factor detectors, portables must be calibrated more frequently due to regular changes in the environment they experience. A typical calibration schedule for a fixed system can be done every three months, twice a year or even annually with stronger units. The typical calibration schedule for portable gas detectors is a daily "bump test" accompanied by monthly calibration. Almost every portable gas detector requires a specific calibration gas available from the manufacturer. In the US, Occupational Safety and Health (OSHA) may set minimum standards for periodic re-calibration.
The challenge test (bump)
Since the gas detector is used for the safety of the worker/worker, it is important to ensure it operates to the manufacturer's specifications. The Australian Standards stipulate that a person who operates a gas detector is strongly advised to check the performance of the gas detector on a daily basis and that it is maintained and used in accordance with manufacturer's instructions and warnings.
The challenge test should consist of exposing the gas detector to the known gas concentration to ensure that the gas detector will respond and that the sound and visual alarm is activated. It is also important to inspect the gas detector for any accident or intentional damage by checking that the housing and screws intact to prevent the ingress of liquids and that the filters are clean, all of which can affect the function of the gas detector. The calibration test device or basic challenge will consist of gas calibration caps/regulators/calibrations and hoses (usually supplied with gas detectors) and a casing for storage and transport. Since 1 out of every 2,500 untested instruments will fail to respond to dangerous gas concentrations, many large companies use automatic test/calibration stations for bump tests and calibrate their gas detectors daily.
Oxygen concentration
Oxygen deficiency gas monitors are used for the safety of employees and labor. Cryogenic substances such as liquid nitrogen (LN2), liquid helium (He), and liquid argon (Ar) are inert and can displace oxygen (O 2 ) in limited space if there is leakage. Rapid oxygen depletion can provide a very dangerous environment for employees, who may not be aware of the problem before they suddenly lose consciousness. With this in mind, oxygen gas monitors are important to have when cryogenics are present. Laboratories, MRI rooms, pharmaceuticals, semiconductors, and cryogenic suppliers are typical users of oxygen monitors.
The oxygen fraction in the respiratory gas is measured by an electro-galvanic oxygen sensor. They can be used stand-alone, for example to determine the proportion of oxygen in a nitrox mix used in scuba diving, or as part of a feedback loop that maintains a constant partial oxygen pressure in the rebreather.
Hydrocarbon and VOC
Detection of hydrocarbons can be based on the mixing properties of gas hydrocarbons - or other volatile organic compounds (VOCs) - and the sensing material incorporated in the sensor. Selectivity and sensitivity depend on the structure of VOC molecules and concentrations; However, it is difficult to design a selective sensor for a single VOC. Many VOC sensors detect using fuel cell method.
VOCs in certain environments or atmospheres can be detected based on different principles and interactions between organic compounds and sensor components. There are electronic devices that can detect ppm concentrations even though they are not very selective. Others can predict with reasonable accuracy the molecular structure of volatile organic compounds in a closed environment or atmosphere and can be used as an accurate monitor of chemical fingerprints and further as a health monitoring device.
Solid phase microextraction technique (SPME) is used to collect VOCs at low concentrations for analysis.
Direct injection mass spectrometry techniques are often used for rapid detection and accurate quantification of VOCs. PTR-MS is one of the most widely used methods for on-line analysis of biogenic and anthropogenic VOCs. Recent PTR-MS instruments based on time-of-flight mass spectrometry have been reported to reach 20 pptv detection limits after 100 ms and 750 ppqv after 1 minute measurement (signal integration) time. The mass resolution of this device is between 7,000 and 10,500 m/m, so it is possible to separate the most common isobaric VOCs and measure them independently.
Ammonia
Ammonia gas continues to be monitored in industrial cooling processes and biological degradation processes, including exhaling breath. Depending on the sensitivity required, different types of sensors are used (eg, fire ionization detector, semiconductor, electrochemical, photonic membrane). Detectors typically operate near exposure limits lower than 25ppm; however, ammonia detection for industrial safety requires continuous monitoring above the fatal exposure limit of 0.1%.
Flammable
- Catalytic bead sensors
- Explosimeter
- Infrared point sensors
- Infrared line detector
More
- The flame ionization detector
- Non-condensive infrared sensor
- Photosionization detector
- Zirconium oxide sensor cell
- Catalytic sensor
- Metal oxide semiconductor
- Gold Movies
- Colorimetric detector tubes
- Sample collection and chemical analysis
- Piezoelectric microcantilever
- Holographic sensor
- Thermal conductivity detector
- Electrochemical gas sensor
Household security
There are several different sensors that can be installed to detect harmful gas in the dwelling. Carbon monoxide is a very dangerous gas, but it is odorless and colorless, making it difficult to detect by humans. The carbon monoxide detector can be purchased for about US $ 20-60. Many local jurisdictions in the United States now require the installation of carbon monoxide detectors other than smoke detectors in residential homes.
Handheld flammable gas detectors can be used to track leaks from natural gas lines, propane tanks, butane tanks, or other flammable gases. This sensor can be purchased for US $ 35-100.
Research
The European Community has endorsed a research project called MINIGAS that is coordinated by the VTT Finland Technical Research Center. This research project aims to develop new types of photonic gas-based sensors, and to support the manufacture of smaller instruments with speeds and sensitivities equal to or higher than conventional lab gas class detectors.
Manufacturer
- DrÃÆ'¤gerwerk
- Gas Clip Technology
- Honeywell Analysis
- Industrial Scientific Corporation
- Mine Safety Equipment
- Oldham
See also
- Gas leak
- Hydrogen sensor
- Sensor list
References
- Installation Guide for Gas Detector System https://www.aesolutions.com.au/blog/gas-detector/a-guide-to-installing-gas-detector-systems.php
- Detcon. Electrochemical Technology. Retrieved 27 February 2010, from http://www.detcon.com/electrochemical01.htm
- Breuer, W, Becker, W, Deprez, J, Drope, E, Schmauch, H. (1979) United States Patent 4141800: Electrochemical gas detector and the same method of use. Retrieved 27 February 2010, from http://www.freepatentsonline.com/4141800.html
- Young, R (2009). "Simulation and measurement of carbon dioxide exhaust emissions using optical fiber-based midpoint sensors". Optical Journal A: Pure and Applied Optics . 11 (1).
- The International Society of Automation. (2003). Infrared gas detector design point guideline. Retrieved February 28, 2010, from http://www.isa.org/Template.cfm?Section=Communities&template=/TaggedPage/DetailDisplay.cfm&ContentID=23377
- Figaro Sensor. (2003). General Information for TGS Sensors. Retrieved on February 28, 2010, from http://www.figarosensor.com/products/general.pdf
- Vitz, E (1995). "Semiconductor Gas Sensors as GC detectors and 'Breathalyzers ' ". Chemical Education Journal . 72 : 920. doi: 10.1021/ed072p920. Ã,
- General Monitor. (n.d.). Infrared Point Detector for Hydrocarbon Gas Detection. Retrieved 25 February 2010, from http://www.generalmonitors.com/downloads/literature/combustible/IR2100_DATA.PDF
- Naranjo, E. (2007). Ultrasonic Gas Leak Detectors. Retrieved 27 February 2010, from http://www.gmigasandflame.com/article_october2007.html
- Configure Gas Detector
External links
- Gas Detection Encyclopedia, Edaphic Scientific Knowledge Base
Source of the article : Wikipedia
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