The coarse fraction may be grinded one more time. The remaining fractions are: .> 250 µ, which will be kept in a plastic bag, and < 250 µ of which processing will be continued. A Calgon (PolyNaPO4) solution will be added for peptisation of the fine particles. Sediment samples are treated in an ultrasonic bath to detach the clay.
Laboratory coat and work gloves must be used, as well as safety glasses and hearing protection. Before starting the air extractor has to be switched on (green button 'in', EK 53 next to the door) and the valve of the machine has to be opened (other valves closed where possible). Check if the mill is clean by opening the door at the front with the handle at the side of the machine.
GRINDING METHOD
In the grinding space 2 hardened disks are assembled of which one is fixed and the other will rotate. The distance between those disks can be adjusted which eventually determines the grain size.
EQUIPMENT
- Sieve (250µ) and collecting container
- Feeler gauge
METHOD
Take care that the door hinges are dust-free (if not the mill will not close tightly and the distance between the disks will recede). Close the mill with the handle. At the back under the engine the adjusting button is located, to set the distance between the discs (0.5 mm). Measure the distance between the disks with the special feeler in the groove on the top of the mill and turn the adjusting button until the distance is correct (0.3, 0.4, 0.5 mm). Place the container to collect the ground sample into the machine. The on/off key is on the front of the mill.
(Small) portions of the sample are inserted into the rotating mill, about 100 cc each time. The collecting container can contain ca 1000cc.
The ground material will be sieved now with 250 µ. The coarse fractions may be ground another time (set disc distance at 0.4 mm) and be sieved. After repeating this procedure not more than 2 times the coarse fraction will be kept separately (assuming it will not get finer). The fraction <250 µ will be stored in a 0,4% Calgon solution.
CLEANING
Finally the mill has to be cleaned thoroughly. Use the wire brush and vacuum cleaner. The sieves used have to be shaken in the ultrasonic cleaner during 1 hour.
The work top and the floor under the mill must be wiped off with a wet cloth.