TPT March 2011

I nspection , T esting & Q uality C ontrol Why measure the climatic conditions? in changes to the recoat time and/or defects in the finished film.

AIR has the capacity to hold a certain amount of moisture as vapour, depending on the temperature. Relative humidity is the proportion of moisture in the air at a given temperature, as a percentage of the maximum amount that can be held by the air at that temperature. As air cools, the capacity to hold moisture is reduced and the relative humidity in the air will increase until the moisture starts to condense out of the air on to surrounding cold surfaces. The dewpoint is the temperature at which condensation occurs for air with a given relative humidity. If the air can be cooled to the dewpoint then the moisture will condense out of the air. More importantly if there is a cold surface at or below the dewpoint temperature the moisture will condense on that surface as a thin film of water molecules. When applying paint it is vital that the substrate is not only clean but also dry in order to achieve the service life of the coating system. The rule of thumb used in the protective coatings industry is that the surface temperature must be at least 3°C above the dewpoint temperature for the surface to be free of moisture from the surrounding air. The monitoring of climatic conditions should not be limited to determining if it is “OK to paint”; changes in temperatures and humidity during the cure process can result

an external magnetic surface temperature probe to monitor continuously. TheElcometer 319 is operated using easy to use menus, allowing the user to quickly set up features such as warning limits, backlight brightness, measurement units, etc, and review statistics and measurement records. Standard versions have a rolling memory of the last 10 readings; Top versions come with a memory capacity for up to 25,000 records in up to 999 separate batches and the Elcometer 319 Top is also supplied with ElcoMaster™ Software allowing users to not only download data from their gauge for instant report generation, but also provides users with a remote Watchguard™ facility which allows remote data monitoring of up to 42 gauges on the PC. The Elcometer 139 Digital Dewpoint meter gauge is ideal for determining if it is safe to paint when substrates are cool and relative humidity is high and there is a risk that water vapour is condensing from the air on to the cool surface that is to be painted. The Elcometer 319 can also be used as a data logger for monitoring the climatic conditions regularly over a long period of time, during the cure of a coating for example. Elcometer Ltd – UK Fax: +44 161 371 6010

The Elcometer 319 Digital Dewpoint meter has been designed to determine if the climatic conditions are appropriate to paint and to monitor the climatic conditions during the cure process. These rugged Dewpoint meters quickly and accurately measure relative humidity (RH %), air temperature (Ta) and surface temperature (Ts) and calculates the dewpoint temperature (Td) and the difference between the surface temperature and the dewpoint temperature (ΔT). Each gauge also calculates the equivalent wet and dry bulb temperatures from the measured values for the convenience of some coating inspection regimes. The new Elcometer 319 Dewpoint Meter has many features to make its use quick, simple and accurate, including Bluetooth ® wireless communication. Available in two models (Standard & Top) the Elcometer 319 can be used as a hand held gauge to measure the climatic conditions or as a stand-alone data logger to monitor conditions over an extended period of time, during the coating cure process for example. The gauge can be held in place on a steel surface for the logging process using magnets attached to the back of the gauge. When used as a data logger the gauge has

Email: sales@elcometer.com Website: www.elcometer.com

The Elcometer 139 Digital Dewpoint meter gauge

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M arch 2011

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