IKA A 11 basic - Manual (Page 15)

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The grinding material must be initially broken down into pieces with a diameter of
1cm (feed granularity 10 mm, the size of a grain of corn is ideal).
Cutting milling:
The A 11 basic with the A 11.2 cutting blade reduces bulky, elastic fibrous and
soft materials with high cellulose content. Mixed goods such as trash must be
free of iron and non-iron metals. the feed material must not be too moist or fatty.
Otherwise the material may adhere to the sides of the grinding container.
Following is a list of some materials that can be reduced:
Leaves, fibers, spices, grain, hops, cardboard, paper, hay, plastics, tobacco, peat,
feed goods, dough and roots.
The feed granularity should be no greater than 10 mm.
For moist and sticky feed material (for example fish, meat), reduction is also
possible by adding water. This prevents the grinding material from adhering to the
walls of the grinding container, and the blades continue to engage the grinding
material.
Note: If water is added, the grinding container should not be filled to more than
50% capacity. The mill must only be used in an upright position in this case (must
not be agitated or turned on its head).
Please note: Materials that are not listed above should only be reduced in the
A 11 basic after confirmation from IKA, especially if there is uncertainty about the
danger of explosion (dust explosion as a result of electrostatic charge).
Working with coolants
Please follow the safety instructions.
Crushing causes the mill feed to heat up. This may not always be desirable as the
mill feed can change when heated (e.g. increased oxidation, loss of moisture,
evaporation of volatile components, etc.).
It may only be possible to crush mill feed which is viscous or has a high fat content
by embrittling using coolants.
The A 11 basic offers two cooling processes:
Dry ice cooling (CO2): approx. –78 °C
First put the feed product into the grinding beaker and then add crushed dry ice.
Thoroughly mix the dry ice with the mill feed. Only attach the drive once the dry ice
is completely vaporized, otherwise high pressure can build up in the grinding chamber.
Please note that the mill feed heats up again extremely quickly during crushing (it
may reach room temperature again after approx. 10 seconds of grinding). You may
have to repeat the process several times if the product is not adequately crushed
after one cooling process.
Liquid nitrogen cooling (N2): approx. –196 °C
Please follow the safety instructions for liquid nitrogen cooling in particular and
always wear your personal protective equipment (safety goggles, protective gloves,
etc.).
Use a beater (A 11.1 or A 11.3) to crush mill feed embrittled with liquid nitrogen.
The cutter (A 11.2) is not recommended for this purpose (becomes blunt quickly).
Grinding beaker A 11.5 (included in delivery) is made of fluoroplastic (ETFE) with a
stainless steel insert.
First pour the feed product into the grinding beaker Pour liquid nitrogen into the
grinding beaker using a suitable Dewar vessel, ensuring that the sample is completely
covered or swimming in liquid nitrogen.Only attach the drive once the nitrogen is
completely vaporized, otherwise high pressure can build up in the grinding chamber.
Please note that the mill feed heats up again extremely quickly during crushing (it
may reach room temperature again after approx. 20 seconds of grinding).
If the feed product has a fine fraction or if the same sample is cooled several
times, use filling funnel A 11.7 (IKA accessories). The funnel is attached to the
grinding beaker before filling and prevents fines from the mill feed from swilling
out of the grinding beaker when you are pouring in the liquid nitrogen and during
vaporization. The funnel’s close - meshed stainless steel wire cloth (mesh size 0.063
mm) retains the fine fraction of the sample and allows you to pour in the nitrogen
more easily.
Caution: The outer edge of the grinding beaker and filling funnel can also get very
cold and must only be handled using personal protective equipment.
Caution: Fill liquid nitrogen only into the grinding beaker! Avoid strictly any contact
of liquid nitrogen with all other parts!
Please note that the grinding beaker can ”ice up”, especially in the case of
repeated cooling. As a result, it may be difficult or even impossible to screw it on. If
so, you will need to ”clean” the grinding beaker, i.e. let it thaw out or wash it in a
dishwasher. Always dry the grinding beaker before using it again.