KERN mlb-c Operating Manual

Contents

KERN mlb-c Operating Manual Manual pdf 57 page image

MLB_C-BA-e-1431 5716 General information concerning moisture analysis16.1 ApplicationIn all cases where moisture is added to or removed from products, a fastdetermination of the moisture content is of enormous importance. For countlessproducts the moisture content is not only a quality feature but also an important costfactor. Very often fixed limits for moisture content apply to the trade in industrial oragricultural goods as well as chemical or food products which are defined by terms ofdelivery and general standards.16.2 BasicsMoisture does not only mean water but includes all substances that evaporate whenheated up. In addition to water this includes,- Fats- Oils- Alcohol- solvent- etc...There are various methods to analyse moisture in a product.KERN MLB uses a method called thermogravimetrics. In accord with this method, thesample is weighed before and after heating, determining the material moisture bylooking at the difference.The conventional drying chamber method follows the same principle, with theexception that this method requires a considerably longer measuring period. . Inaccord with the drying chamber method, the sample is heated from the outside to theinside by a hot air current, so as to remove the moisture. The radiation applied in theKERN MLB penetrates mainly the sample in order to be transformed inside it intoheat energy that is, warming from the inside to the outside. A minor amount ofradiation is reflected by the sample, a reflection that is less in dark samples than inlight-coloured ones. The depth of penetration of the radiation depends on thepermeability of the sample. In samples of low permeability the radiation onlypenetrates the outer layers of the sample, possibly resulting in imperfect drying,incrustation or burning. For that reason the preparation of a sample is of greatimportance.16.3 Adjustment to existing measuring methodQuite frequently the KERN MLB replaces a different drying method (such as a dryingchamber) as the KERN MLB achieves shorter measuring times during a simplifiedoperation. For that reason the conventional measuring method must be matched tothe KERN MLB in order to achieve comparable results.• Carry out parallel measurementLower temperature setting for KERN MLB than drying chamber method• Result of KERN MLB does not match reference- Repeat measurement with changed temperature setting- Vary shutoff criterion