The selection and use of flammable gas detectors pdf hse. Sensepoint lel combustible sensor operating instructions. An lel detector or lel meter detects dangerous levels of a combustible gas or solvent vapor in air, expressed in percent lower explosive limit, or lel. A gas detector is a device that detects the presence of gases in an area, often as part of a safety system. May 01, 2004 in other words, if a combustible gas sensor that has been calibrated to propane is exposed to 32% lel methane, the response will be equal to that of 50% lel propane. This limit varies with the type of gas and with the oxygen concentration of the air in which the flammable gas is mixed. Since the reactants are all gaseous, the reaction takes. Sensor openings and water barriers must be kept clean. When the movement of the magnet comes close to the reed switch or reed sensor the cont. Class i, zone 1, aex ia iic t4 with ir sensor athe ec type examination certificate is demko 07 atex 0626395x. Response of catalytic type cc lel sensor to various combustible gases.
The switch locations are indicated by menu and select. The reed level sensor in its simplest form is composed of a magnet and a reed switch or reed sensor. The sensor assembly consists of an explosion proof enclosure housing rated for hazardous locations and a replaceable sensor module. Carbon monoxide, for example, has a tlv of 25 ppm and also has a lower explosive limit lel of 12. The lower their flashpoint, the more dangerous they are. Correction factors for combustible gas lel sensors note. Sensor type detects lel range c1c5 hydrocarbon gases methane, ethane, propane, butane, pentane, natural gas detects lel range c6c9 hydrocarbon gases hexane, heptanes, octane, nonane detects lel range heavy fuel vapors diesel, jet fuel, kerosene, etc. In the case of sensor inhibitors the effects may be reversible, and the sensor may recover over time at least to an extent. Refer to sensor separation on page 12 for instructions. The following table shows the benefits of each sensor and the combustible gases it will detect.
An lel detector is an essential component of a fixed gas detection safety instrument for lel safety and so monitors, indicates and alarms when levels of lel exceed 0% to indicate the presence of combustible gas or solvent vapor. An lel monitor is also referred to as an lel gas detection system, lel gas detector or simply a fixed gas detection system. Monitoring flammable vapors and gases in industrial. What kinds of sensors are used to detect lel combustible gas. Sensepoint is a sealed disposable sensor for the detection of flammable.
This sensor mustonly be used with a millennium ii series transmitter. If the catalyst is harmed by exposure to sensor poisons or inhibitors, the sensors ability to detect gas is affected. How infrared sensors measure lel combustible gas 20140903. Lower and upper explosive limits for flammable gases and vapors before a fire or explosion can occur, three conditions must be met simultaneously.
When the magnet is moved away, the contacts will open. The different types of gas sensors technologies including catalytic gas sensor, electrochemical gas sensors, thermal conductivity gas sensor, optical gas sensor and acoustic gas sensor are. Refer to the instrument settings and product manuals for information specific to each instrument. The minimum concentration of a flammable gas in air capable of igniting is called the lower explosive limit, or lel. Honeywell sensepoint gas sensors technical handbook. Is an lel sensor dependable in an h2s lel environment. Handling lel sensor poisons it is well known that certain chemicals inhibit or poison the catalytic bead in lel combustible sensors, leading to partial or complete. Where the user calibrates any sensor using a different gas, responsibility for identifying and recording calibration rests with the user.
A gas detector can sound an alarm to operators in the area where the leak is. This disambiguation page lists articles associated with the title lel. Reported values of the lower explosive limit for jet fuels range from about 0. Determining which sensing technology is the best fit for your individual application is extremely important. If an internal link led you here, you may wish to change. This includes a brief description of the operating principle and some of the advantages and disadvantages of each type. Infrared combustible gas sensor module 510028it infrared combustible gas detector 510028it sierra monitors infrared fixed gas detector, the 510028it, monitors combustible gases such as methane and propane, detecting and alarming users when gases reach between 0 to 100% lower explosive limit lel concentrations.
Below the lfl, the mixture of fuel and air is too lean to support combustion. Type of sensor 12 there are a number of different types of sensors used for gas detection. The sensor components consist of a pair of platinum heating coils embedded in a catalyst. Vapour lel lel flash vapour ignition in in point pressure temperature.
In actuality, many gases are both toxic and combustible. Two types of sensepoint gas sensor are available one for combustible. Sensor selection gas monitoring generally consists of two categories. If the sensor is connected to any other model of transmitter, it will not function and may result in the sensor or transmitter being damaged. Infrared sensor for sensing gas at lel levels, see section 6. Portable and fixed gas detectors lel gas monitors dod. Based on different sensor types drager offers three versions for different applications. The combustible gas sensor type comes in three different versions standard lel, high.
Combustible gases in the lel range with the sensitivity dependent on gas type. Sensorguard technology protects against exposures to high gas concentrations allowing a full 5 year warranty on the sc310 sensor. However, we have been unable to confirm this result and recommend using a pid as a much more accurate method of measuring lel for jet and diesel fuels. This is well before a combustible fuelair mixture exists near the lel analyzer. Lower and upper explosive limits for flammable gases and vapors. But remember, no single type of sensor can detect all types of dangerous gases and vapors. The flashpoint is defined by the liquids temperature dependent vapour pressure and its lel. Ppm for acrylonitrile, ethylene oxide, nmethyl pyrolidone, methylene chloride, and many others. The lower their lower explosion limit lel, the more dangerous they. More information on point detectors is available in. Poisoning is defined as a permanent degradation, while inhibition is usually recoverable by exposure to clean air.
Midaselel 5 year extended warranty sensor technology pellistor catalytic bead measuring range 0 100% lel1 minimum alarm 1 set point 9% lel repeatability detects combustibles, sensor range 0 to 100% or 0 to 5% vol 1tan2. This is a guideline document for calculating correction factors of lel sensors. Sensor for sensing gas at ppm or lel levels, see table 3 for sensor types magnetic switches control the instrument maintenance functions. Confined space instruments almost always include a sensor used to measure percent lel combustible gas. Henderson the potential presence of combustible gases and vapors is one of the most common of all categories of atmospheric hazards. When used in manual calibration mode, instrument calibration. If further details are required that do not appear in this manual, contact. The lower their lower explosion limit lel, the more dangerous they are. There are two types of widely used lel sensors confined space instruments almost always include a sensor used to measure percent lel combustible gas.
Sep 03, 2014 nondispersive infrared ndir sensors are increasingly being used in multisensor instruments to measure lel combustible gas. For all flammable gas types, % lel detection is fast and reliable with simplified field serviceability using the m2b, m21, or m22 universal transmitters. Drager gas list 2018 list of detectable gases and vapours. The user is encouraged to calibrate the instrument with the target gas for most accurate readings. When the sensepoint combustible lel sensor is to be. Sensors designed to detect the dangerous presence of combustible gases are therefore called lel sensors. They are also suitable for use in a broad variety of field application environments see table 1 for a list of gases typically monitored. Understanding catalytic lel combustible gas sensor performance. Refer to the relevant control system manual for connection. The selection and use of flammable gas detectors the main types of sensor are listed in the appendix. Sd1 series combustible gas and organic vapor detector transmitter.
The lel sensor depends on the activity of the catalyst to detect gas. Flammable group hydrogen, methane midasslel, midashlel. Monitoring flammable vapors and gases in industrial processes. Lel and uel are heavily dependant on atmospheric conditions. Lel sensor types there are several lel sensor types available for the monitor. Some types of gas monitors and detectors worth considering are.
If for the substance in question the calibration chamber procedure is applicable the value of the amount to be inserted into the 3 litres calibration. Toxic gas monitoring and combustible gas monitoring. Sensor types methane propane measuring range 100 to 20. Sudden changes in atmospheric pressure may cause temporary fluctuations in the oxygen reading. An earlier thirdparty test reported a cf for jet fuels of 3. A single gas detector is often more costeffective than a multigas detector. Sc310 catalytic bead combustible gas sensor accessories and ordering information 5. Understanding combustible sensor performance by robert e. The sensing heads are intended to be used in the harsh industrial environment and connected to a suitable central controller by means of a 3core cable. Letitia elizabeth landon 18021838, english writer better known as l. Infrared combustible gas sensor infrared gas detector. Customers looking for gas leak detection equipment know they can rely on us to keep their workers from being exposed to harmful. An lel monitor is an instrument used to detect hazardous levels of a combustible gas or solvent vapor in air, expressed in % lel, or lower explosive limit. Catalytic combustible gas sensors international sensor technology.
An lel detector is an integral part of a complete gas detection system and can be referred to as a gas detector or just a fixed gas detection system. A magnetic field pulse is applied by momentarily putting the end of the magnet in proximity to the switch and then removing it. Manufacturers offer different types of sensors to measure combustible gas and voc vapors. This type of equipment is used to detect a gas leak or other emissions and can interface with a control system so a process can be automatically shut down. Obstruction of the sensor openings or contamination of the water barriers may cause readings to be lower than actual gas concentrations. Gas detector heads portable gas sensors rki instruments. Detects heavy fuel vapors in low ppm range diesel, jet fuel, kerosene, etc. It stands to reason that the sensors used to measure combustible gases are the most.