Accidental Evaporation
Accidental evaporation of water during the mechanical sampling of large fiber bales can lead to inaccurate weight records. Thermal core drill moisture loss occurs when the friction from a high-speed sampling drill generates heat as it penetrates deep into the compressed wool or cotton. This heat causes a portion of the natural moisture in the fiber to turn into vapor and escape before the sample can be sealed.
Friction Heating
Surface temperature of the drill bit can rise rapidly during the extraction of a core from a dense bale. If the operator uses a dull bit or excessive speed, the thermal core drill moisture loss increases, making the sample appear drier than the rest of the shipment. This error results in an underestimation of the total moisture regain for the entire lot.
Audit Adjustment
Independent testers use correction factors or specialized low-friction equipment to minimize the impact of this phenomenon. When thermal core drill moisture loss is suspected, the laboratory may compare the core results with samples taken by hand from the surface. Any discrepancy between these two sets of data must be resolved to ensure the buyer is not overcharged for missing mass.
Mitigation Strategy
Sharpening the cutting edge of the drill and reducing the rotation speed are effective ways to control the temperature. Some advanced sampling tools use cooled bits or vacuum systems to capture the sample without heating it. Accurate results depend on the speed with which the technician transfers the core from the drill into an airtight container for weighing.
