Gas Detection 11


The X-am 7000 can detect methane in concentrations around the lower explosive level (LEL) using a catalytic sensor. Many of the odorants added to natural gas can also be measured using the Dräger odorant sensor. In this application, the instrument is also able to detect toxic hazards caused by carbon monoxide and hydrogen sulphide. An ideal solution for facility checks and monitoring measurements is the instrument's leak detection mode. In this mode, the display switches from normal display to a graphic display – the bar chart advancing in 50 ppm steps (Figure 4).


This function is supported by an ascending or descending tone to reflect the gas concentration, similar to that used in a Geiger counter. Thanks to the flexible goose-neck probe, even difficult to access areas can be reached in comfort.


Figure 4.


seen through 360 degrees, helping to ensure the alarm will be noticed. In addition, maximum concentrations, e.g. TVA and STEV values, can be quickly checked.


Leak detection in gas pipelines


Natural gas is highly flammable, so gas plants and pipelines must be subjected to regular maintenance to prevent explosions. Natural gas cannot be detected by smell, so strongly smelling odorants are added to the gas. Since the odour threshold of these odorants is extremely low, even small leaks can be detected. Mercaptans are commonly used as odorants.


Approvals


The Dräger X-am 7000 features a declaration of conformity with EC type examination certificate in accordance with the provisions of ATEX Directive 94/9/EC, and protection classes II 2G EEx ia d IIC T4 and I M2 EEx ia d I. The instrument's electromagnetic compatibility has been tested in accordance with Directive 89/336/EEC, and the instrument is CE marked. For the USA, this instrument is UL approved as Class I, Div 1, Group A, B, C and D. It can be used in a temperature range from -20 to +60 °C.


AUTHOR DETAILS Ulf Ostermann


Draeger Safety Asia Pte Ltd 67 Ayer Rajah Crescent #06-03


Singapore 139950 Tel


Fax


+65 6872 9281 +65 6773 2033


www.draeger.com


New Infrared Methane Sensor


City Technology (UK) is pleased to announce the expansion of its range of IRceL® addition of a methane sensor – IRceL®


infrared sensors with the CH4


. Infrared sensors


are being increasingly used in place of pellistors for detecting flammable gases in both fixed and portable gas detectors. Although infrared sensors are not directly analogous to pellistors (they don’t measure combustion


and will not detect H2 for instance) they have the benefits of long-life, not being susceptible to poisoning, operating in anaerobic conditions and they fail “safe”. Consequently infrared based sensors for detecting a range of hydrocarbons are being increasingly used in certain applications. City Technology’s new methane sensor, IRceL®


CH4, is in the industry standard 4 Series format and is fully certified to flameproof and intrinsically safe standards.


The IRceL® CH4 has been designed to deliver the best


possible performance and uses high quality optical components comprising a long-life tungsten filament bulb as the IR source and a dual channel pyroelectric detector (reference and detector). The novel non focusing optical design, offers significant improve-ments in performance over other optical designs enabling the sensor to operate reliably and reproducibly across a wide temperature range. Like all the IRceL® range, the methane sensor contains an embedded EEPROM that contains device specific calibration factors which, when used together with City Tech-nology’s algorithms for signal linearization and temperature com pensation, allow the instrument to perform with industry leading accuracy virtually unaffected by temperature.


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Ion Science Exhibit at OSEA


Ion Science, the UK based gas detection manufacturers, will be exhibiting at OSEA, which this year is taking place at Suntec, Singapore, from 2 to 5 December. The first event took place back in 1979 - and now the biannual event is one of the best recognised and regarded events in Asia for the oil and gas industry. This year Ion Science will be exhibiting their market leading Hydrosteel range. Hydrosteel can measure hydrogen flux – which can be a key indicator of corrosion in steel pipework.


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One-Man Calibration of Gas Measuring Systems in Areas Subject to Explosion Hazards


Due to heightened safety requirements, regular function inspections and calibration are imperative in areas subject to explosion hazards. Since this work can usually, however, only be carried out when the device is open, the plant may have to be shut down to create a safe atmosphere and to prevent ignition by potential sparks. Apart from the logistics problems this causes, there are also the additional costs involved in a loss of production. For this application J. Dittrich Elektronic (Germany) manufactures the explosion-proof gas measuring system MF420- Ex. Since the housing does not need to be opened, it allows one-man calibration at the place of installation in a potentially explosive atmosphere. Calibration takes place by means of two covered pushbuttons on the housing, synthetic air and test gas. A four-digit, alphanumeric display indicates the measured value as well as possible malfunctions of the sensor and electronics.


MF420-Ex is equipped either with a pellistor to detect explosive gases and vapours or with a specific electrochemical sensor to detect toxic gases and vapours. The measuring system is easily wall mounted by means of a separate mounting flange. Processing and output of the measurement signals (linear current output, 4-20 mA) are integrated. Power is supplied via 24 V direct current. The device is approved for use in areas subject to explosion hazards and has the EC Type Examination Certificate in accordance with Directive 94/9/EC (ATEX100a). In Germany and Switzerland the MF420-Ex detects leakage points on gas pipes, petrol tanks and in paint storage warehouses. On container ships transporting solvents, it detects any explosive vapours that might possibly escape from the containers. In China the MF420-Ex promptly identifies any explosive gas-air mixtures that might occur in biogas plants.


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