FRITSCH PULVERISETTE 13 classic line - Manual (Page 24)

6.3 Grinding with grinding disks of zirconium oxide
When grinding with zirconium oxide grinding disks, certain work precau-
tions need to be observed:
1.
Precise setting of the smallest gap. The disks may under no circum-
stances touch each other during the grinding. The local heating
promptly causes tension fissures at the circumference. These fis-
sures appear very quickly and are easily detected.
2. Local heating can also occur if you fill in so much material that a
comminution of a bed of material takes place constantly on the
outer edges of the grinding disk (grinding gap completely filled
with sample material). This leads to tension fissures at the grinding
disk's circumference and even its breaking.
3. The hardness of the zirconium oxide grinding disk is 8.5 Mohs
(HV1350). No harder sample material may be comminuted (max-
imum Mohs hardness of 7), because this causes the outer edges of
the grinding disk to break.
4. Proceed very cautiously when grinding with zirconium oxide
grinding disks. You should pre-crush the grinding stock in a first
pass with a larger gap width, before achieving the desired fineness
with the smallest gap in a second pass. If you do not have any
information about the grindability of your material, carry out pre-
liminary tests with small sample quantities. The grinding disks
have a progressing breakage geometry. Rough comminution takes
place in the inner area and fine comminution takes place in the
outer area of the grinding disk. The stress is greatest in the area of
the fine comminution. The described breakage could occur here
with very hard sample materials.
5. The adhesive used to glue the fastening bolts into the zirconium
oxide grinding disks has a temperature resistance of up to 80 °C.
The grinding disks should therefore not be heated to above 80 °C
so that a firm seat in the mount is ensured.
6. Please observe the operating instructions concerning the
mounting and removing of the grinding disks. Ä Chapter 9.3
‘Exchanging the grinding disks’ on page 34
NOTICE!
Fritsch GmbH guarantees that it delivers zirconium oxide
grinding disks of only the utmost quality.
Used grinding disks that are cracked at the circumference,
chipped or completely broken cannot be recognised for
claims.
Using the device
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