FRITSCH PULVERISETTE 7 premium line - Manual (Page 30)

Be extremely careful if solvents are used. 60 ml isopropanol in an 80 ml
grinding bowl results in the development of the following pressure and
temperature:
Temperature of grinding bowl
wall [°C]
Pressure in the grinding bowl
[bar]
50 1
73 2
86 5
109 8
124 10.5
132 13
139 14
148 19
149 20
The overpressure limit for fluororubber flat seals is reached at 120 °C
and for silicone seals at 149 °C.
Here is an example of the pressure and temperature development
during an actual grinding operation:
Grinding balls: 120 g 0.4-0.7 mm ZrO
2
Grinding bowl: 80 ml ZrO
2
Material to be ground: 10 g aluminium oxide with feed size d
50
=20 µm
Addition: 30 ml water
Speed: 1100 rpm
Time [min] Bowl 1 [°C] Bowl 2 [°C]
10 124 119
15 140 136
Other configurations or material to be ground may result in high temper-
atures being reached much sooner.
Because the gases and solids are mixed completely in the
grinding bowl, pure gas is never discharged. Material to be
ground is also discharged. To clean the mills, see
Ä Chapter 8 ‘Cleaning’ on page 101.
Using the device
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