How to Prepare a Moisture Analyzer

October 18th, 2010

A moisture analyzer is a valuable tool to help organizations maintain correct moisture content across a broad range of industries.  Optimum moisture content is set by industry trade associations and government agencies to insure efficient processing of products such as plastics and bone meal to maximizing shelf life of food and pharmaceutical products.

Moisture Content Defined

The term “moisture” generally refers to water – the percentage of the net weight of a product or material that is due to water content.  But it also includes anything that can evaporate on heating.  Examples include fats, oils, alcohol and solvents.  Most simply stated a moisture analyzer such as the Kern MLB available from Tovatech calculates moisture content by comparing the weight of a sample before it is dried on heating with the weight after the drying process is completed.  It consists of a halogen heater mounted on a precision scale.

Based on established processes for a particular product, the moisture analyzer is programmed by time and temperature.  Carefully prepared samples are placed in the moisture balance and the unit is started.  The halogen heater quickly drives off moisture while the balance displays the status of each stage of the process.  Moisture analysis automatically terminates when the dry weight is stable or after a specified time.  The moisture content is posted on the unit’s display panel along with the heating mode, temperature and time.

Selecting a Heating Mode

Not all substances react equally to a moisture analyzer.  Because of this the heating mode or profile should also be programmed into the unit.  The most commonly used mode is standard drying, which is suitable for most substances.  The soft drying mode is recommended for samples that do not tolerate the full power of the halogen heater.  This helps protect sensitive samples from decomposing or forming a protective “skin.”  In the soft drying cycle samples are heated evenly from the outside to the inside by heat convection.

For samples with moisture content between 5% and 15% a fast drying cycle can be programmed into the unit.  With this setting the halogen heater quickly raises the temperature to approximately 40% above the set temperature, and then returns it to the set temperature.

Step drying, also requiring an initial minimum 15% moisture content, is used for samples that exhibit specific behavior during drying.  Individual increments on time and temperature are programmed into the moisture analyzer.

All operating procedures and practices for using a moisture analyzer must be carefully spelled out in company manuals.  These will range from sample preparation to maintenance to record keeping.  In the latter case, all relevant data can be printed or transferred to a PC via an RS 232 interface.

Contact the scientists at Tovatech for additional information in selecting, setting up and operating a Kern moisture analyzer.

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What procedures are in place in your company for confirming moisture content?  How often are samples taken?


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