Michell Instruments CDP301 portable hydrocarbon and water dewpoint analyser

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Michell Instruments’ CDP301 is useful for quality control in natural gas processing and transmission, as a manual-visual dewpoint instrument that uses the chilled mirror technique for measurement of both hydrocarbon and water dewpoint. It is ATEX, IECEx and cQPSus compliant for use in a Zone 1 or 2 Hazardous Area and Class I, Div 1 Hazardous Locations, allowing it to be positioned close to the process sample test point. It is fully portable, simple to set up and, as it is fully self-contained, there is no need to use a separate coolant gas.

Unlike older visual-manual dewpoint testers, which rely on the operator making observations through a microscope, the CDP301 includes a full-colour interface that shows a magnified view of the mirror surface. It is this optimised display — together with specific illumination techniques — that makes it possible to measure either water or hydrocarbon dewpoint and log the results. Visible red-spectrum laser light clearly illuminates fine water droplets and ice crystals when targeting water dewpoint. Broader spectrum white light enables the iridescent film synonymous with HC condensate to be detected with a high sensitivity of up to 5 mg/Nm³.

Once the user has observed a layer of condensation form on the mirror surface, the temperature, pressure and dewpoint are recorded at the push of a button. The video footage and/or still images, along with corresponding data for multiple measurement cycles, are logged for later review either on the instrument’s display or on a PC.

The dewpoint tester meets the requirements of ASTM D1142 (standard test method for water vapour content of gaseous fuels by measurement of dewpoint temperature) and ISO6327 (determination of natural gas dewpoint using the cooled surface condensations method). The cooling rate of the mirror surface is carefully controlled to enable sensitive detection and repeatable measurements in accordance with the relevant ASTM and ISO test methods specific to dewpoint in natural gas.

The Peltier-cooled sensor designed specifically for the CDP301 features thermal characteristics to offer cooling depression by up to 70°C below ambient operating temperature, even when performing tests at high analysis pressure up to 100 barg. The tester weighs just 8 kg and its rechargeable battery allows up to 8 h of use, so it can be used in remote locations where access to power is not always guaranteed.