Perform a pre-embrittlement of elastic and tough sample material as follows:
Pre-embrittlement of sample material for grinding must be done indirectly.
Use only grinding balls and grinding jars made of stainless or hardened steel for
cryogenic grinding with the cryokit. Grinding balls and grinding jars made of
zirconium oxide or tungsten carbide are not suitable for direct contact with liquid
nitrogen. The rapid cooling may cause cracks or fractures.
For this purpose, the sample material must be filled into a grinding jar (steel) together with
the grinding balls (steel) and the grinding jar (steel) must be tightly closed.
Subsequently, the tightly closed grinding jar (steel) with the grinding jar supports of the
cryokit is immersed in a bath of liquid nitrogen until it stops bubbling.
Thus, the sample material inside the grinding jar (steel) is also chilled and ready for
grinding.
WARNING Under no circumstances liquid nitrogen or dry ice should be filled into the
grinding jar and then close it. The resulting overpressure in the grinding jar would burst it open.
6.10.2 Wet Grinding with Highly Flammable Materials
Damage to the device caused by liquids
Penetration of liquids into the interior of the device
− Mechanical and electronic components are damaged and the proper
function of the device is no longer guaranteed.
• Make sure that no liquids get into the interior of the device!
Dfd
Wet grinding using highly flammable materials is permitted with this device if certain
precautionary measures are complied with.
When using highly flammable materials such as hexane, isopropyl, ethanol, benzine etc. as a
grinding aid , the inside of the grinding jars should be classed as Zone 0, i.e. as a permanent
explosive mixture.
It is therefore necessary to prevent potentially explosive vapours escaping from the clamped
grinding jars during a grinding process or being able to reach places which have the necessary
ignition energy. These vapours are in particular also pressed outwards by the temperature rise
that takes place and by the consequent increase in pressure inside the grinding jar.
For this reason we urgently recommend that the user of the device (the employer) assesses the
existing hazards within a coherent explosion protection concept according to local conditions
before using such solvents and, where necessary, records supplementary organisational
measures in an explosion protection document.
This approach is regulated in the EU under Articles 118 and 118a of EC Directive 89/391/EEC.
Account must be taken of corresponding provisions in other countries outside the EU.
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