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modern devices for gas detection

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Gas Detection -New TechniquesHarmful gases in the mines are Carbon dioxide(CO2) Carbon Monoxide (CO) Methane (CH4) Hydrogen (H2) Hydrogen sulphide (H2S) Nitrous fumes

Gas Detection Techniques

Objectives To ensure environmental air quality To ensure dilution of blasting fumes To detect early symptoms of spontaneous heating/fire To assess air composition behind sealed off/sectional areas To conduct blasting operations in free

Techniques

Mode of Measurement Conventional system Air samples analysis Tube type detectors Digital Gas Detectors Gas Chromatograph

Techniques

Mode of Measurement Conventional system Flame safety lamp Cannery birds Smell indications physiological symptoms

Techniques

Mode of Measurement Air sample analysis Collection of samples Condition of sampling pippets Transportation time Analysis time Nitrogen calculation by difference

Techniques

Mode of Measurement Types of Digital gas detectors Various types of portable and transportable gas detection apparatus may be used in a variety of ways according to their particular design and specification. Persons required to use digital gas detectors should have been properly trained in its used and should have ready access to the operating instructions.

Techniques

Types of Digital gas detectors Explosimeter Oxymeter Toximeter Multi gas detector Chip measurement system(cms)

Techniques

Sensor TechnologySensors are available for measurement of explosive, toxic and environmentally harmful gases and Oxygen

Techniques

Sensor TechnologyTypes of sensors: 1. Electrochemical Sensors 2. a) Catalytic oxidation sensors (Cat Ex) b) thermal conductivity sensors (heat of reaction) for measuring combustible gases. 3) Infrared sensors (IR) for CO2 and Ex versions

Techniques

Electrochemical Sensorssensors are transducers Electrochemical for measuring the partial pressure of toxic gasses or oxygen in the ambient air The ambient air to be measured diffuses through a plastic membrane into the liquid electrolyte of the sensor. electrolyte enclosure, there is a measurement In the electrode, a counter electrode, and a reference electrode.

Techniques

An external electronic potentiostat ensures a constant voltage between the measurement electrode and the reference electrode The voltages, electrolyte and electrode materials are so chosen that the gas to be measured is converted electrochemically at the measurement electrode while at the same time a current flows through the sensor. The current is proportional to the partial pressure of the gas being measured.

Electrochemical Sensors

Techniques

Electrochemical Sensors Simultaneously, at the counter electrode, an electrochemical reaction with oxygen from the ambient air takes place For oxygen, this voltage, the electrolyte and the electrode material are selected such that oxygen is electronically converted at the measuring electrode. During this process, a current flows which is proportional to the oxygen concentration O2+4H+4e-=2H2O

Techniques

Electrochemical Sensors For toxic gases, the bias is selected such that H2S or CO contained in the sampling air is oxidized at the anode in accordance with H2S + H2O = H2SO2 + 8H + 8eor CO + H2O = CO2 +2H + 2e Whereby the current flowing thorough the sensor is proportional to the H2S or CO concentration respectively.

Techniques

Catalytic Sensors

The catalytic sensor is a transducer for the measurement of the partial pressure of flammable gases and vapours in the atmosphere. This sensor functions according to the thermal heat of reaction principle. The ambient air to be measured diffuses through a sintered metal disc into the sensor, where the flammable gases are then burned catalytically on a heated detector element (Catalytic bead).

Techniques

Catalytic Sensors The oxygen needed to support this burning process is taken from the ambient air. The heat generated by the burning process causes the detector element to heat up further. This heating changes the resistance of the detector element to heat up proportionally to the concentration of the flammable gases . The voltage measured at the sensor is amplified by the electronics and is displayed in % LEL.

Techniques

Infrared Sensors Various compounds absorb infrared energy. They absorb different wavelengths of IR light energy in different degrees. Higher concentrations of gas will absorb more IR light energy. Gas is pumped, or diffused into a chamber with an IR light source. The infrared sensor is a transducer for the measurement of the partial pressure of ambient gases. This sensor functions according to the principle of the absorption of infrared light.

Techniques

Digital Detectors

Oxymeter/toximeter(Pac-III) Pac: Personnel Air Control Single portable gas detection instrument for measuring toxic gases, vapours and oxygen. Technical specifications:

DIMENSIONS : 66 x 110 x 32 mm CARBON MONOXIDE 0-2000 PPM WEIGHT : 185 g OXYGEN 0-25 % OPERATING HUMIDITY : 10-95 % (RH) Vol.

RANGE OF SENSORS(ELECTROCHEMICAL)

Techniques

Display: Instrument type, software version, date and time, gas type, measuring range, alarm set points, pre-alarm and final alarm, measured value and measuring unit. All these features make it convenient when fitting different sensors and for proper calibration of the equipment. The next calibration date is also displayed. An illuminated display is provided to see in dark.

Oxymeter/toximeter(PacIII)

Techniques

Digital Detectors

Oxymeter/toximeter(Pac-III)two audio- visual alarms are provided the Alarms: limits of which are adjustable as per the user needs.The pre-alarm is non-latching and the main alarm is latching. Self- Test Check: the instrument is provided with selfdiagnostics and does a self-test check for the circuits and power supply during starting. Warning signals and error messages for measuring errors, instruments errors, on exceeding measuring range and also in case microprocessor fault.

Techniques

Digital Detectors

Oxymeter/toximeter(Pac-III) Power supply: operated with alkaline/lituium/NiCd battery. The instrument displays battery status , indicates battery replacement, charging status and also gives an alarm for dead battery and automatically shuts down to prevent battery damage. Operating time: 24 hours Charging time: 10 hours Calibration: It enables span calibration, standard calibration, zero calibration, sensitivity calibration and alarm for no calibration possible.

Techniques

Digital Detectors

Oxymeter/toximeter(Pac-III)Advantages: If different gas hazards need to be measured, a number of different electrochemical sensors can be kept ready at hand which can simply be connected to the devices as needed. The flexibility of this measurement system guarantees compatibility with future extensions like new sensors or other accessories.

Techniques

Digital Detectors

Methonometer( Pac-Ex) It is versatile pocket-size instrument for explosive atmospheres in %LEL. The instrument can also measure methane in % by Vol. It is user -friendly and adjustable. Technical FeaturesMeasuring range 0-100% LEL, resolution 1% 0-5%Vol CH4, resolution 0.001% Vol. 5- 100% Vol CH4, resolution 1% vol.

Techniques

Digital Detectors

Methonometer( Pac-Ex) It is possible to change the measuring range from LEL to Vol % and vice-versa. Sensor: Plug-in type pellistor sensor which measures by heat of combustion and thermal conductivity. Sensors life is 3 years. Size : 142 x 66 x 27 mm weight : 370 g Operating Humidity : 5-95% RH

Techniques

Digital Detectors

Methonometer( Pac-Ex) Self- Test Check: the instrument is provided with self-diagnostics and does a self-test check for the circuits and power supply during starting. Alarms: It has four gas concentration thresholds fully adjustable with pre-alarm is non-latching and main alarm is latching.

Techniques

Digital Detectors

Methonometer( Pac-Ex)

Power supply: it works with NiCd rechargeable battery. It has an intelligent battery management system. The instrument displays battery status, charging, gives and alarm before 10 min. operating time left for the battery and automatically shuts down with 2 min. to prevent battery damage. Operating time: 8 hours Charging time: 8 hours

Techniques

Digital Detectors

Multi gas detector( Miniwarn) It is a portable multi-gas measuring instrument for continuous monitoring of the concentration of several gases in ambient air. It can independently measure simultaneously four selected gases depending on the installed sensors. Multifunctional software menu is operated by a three-button key pad. It allows automatic configuration of the instrument according to the installed sensors.

Techniques

Digital Detectors

Multi gas detector( Miniwarn) Sensors: Plug-in sensors consisting of one catalytic sensor and three Electro- chemical sensors, one each for carbon monoxide, carbon dioxide and oxygen. Measuring rangesCatalytic explosive Sensor for Methane Carbon Monoxide sensor Carbon Dioxide sensor Oxygen Sensor 0-5% Vol. 0-100% LEL & 5 to 100% Vol. 0-2000 PPM 0-5 % Vol. 0-25% Vol.

Techniques

Multi gas detector( Miniwarn) Display: It continuously monitors and displays complete instrument information including battery capacity, alarm settings, measuring ranges, instrument fault, sensor fault, calibration information, date and time, instrument warnings, battery alarms etc. The information is also displayed by means of special symbols. Alarms:Audio -visual alarm ac

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