Explosion hazard from hybrid mixtures
Hybrid mixtures are mixtures of ammable dusts with explosive gas/air atmospheres which can
together create a dangerous explosive atmosphere if they occur at the same time. Changes can
arise in the safety performance characteristics here, such as a change in the zonal classication,
increase in the explosion pressure, reduction in the minimum ignition energy and a reduction in
the maximum temperatures to be complied with.
An explosion can occur. This can result in death, serious injury or material damage.
• For this reason, the relative characteristics must be considered both for gas (zones 0, 1 and
2) and for dust (zones 20,21 and 22) where hybrid mixtures arise. It is necessary for a
competent assessor to determine in the individual case whether the parameters determining
ignition are unfavorably aected in a particular hybrid mixture.
• Motors with dual plates for G (“Gas”) and D (“Dust”) may only be used where these two occur
after prior examination of the properties of the hybrid mixtures by the user.
• These explosion-protected machines are not suitable for hybrid explosive environments. Use
in atmospheres where there is a risk of explosion caused by both gas and dust simultaneously
is absolutely prohibited.
Risk of explosion when used in the incorrect zone
Only install machines with type of protection increased safety "e" or "eb" and machines "nA" or
"ec" in hazardous zones, carefully complying with the regulations laid down by the responsible
regulatory body. The responsible regulatory body is responsible for determining the level of
explosion hazard (classifying zones).
Risk of explosion when the operating mode is not complied with
If there are no other specications in the EU-type examination certicate or on the rating plate
regarding operating mode and tolerance, electrical machines are designed for continuous duty
and normal starting procedures that are performed infrequently and do not result in an
excessive temperature rise. Only use these machines for the operating mode specied on the
rating plate.
See also
Thermal protection (Page51)
Explosion hazard due to overheating of the machine caused by a layer of dust
Deposits of dust have a thermal insulation eect, which can lead to the machine overheating.
The maximum surface temperature of the machine cannot be adhered to. The dust can ignite,
resulting in an explosion. This can result in death, serious injury or material damage.
• Dust the machine regularly.
• Do not allow dust layers thicker than 5mm to build up on the machine surface.
• Do not switch the machine on until the dust has been removed.
Operation
8.1Safety instructions for operation
1MB..1/2/3/4 - shaft heights 63 ... 355
106 Operating Instructions, 11/2023, A5E52779900A
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