05
MIETZSCH GmbH Lufttechnik Dresden
Großenhainer Str. 137
01129 Dresden
Fax (0351) 8 58 00 74
http://www.mietzsch.de
EXPLOSION PROTECTION
Guideline 94/9/EG (
ATEX
) newly regulates explosion protection for non-electrical devices from July 1, 2003. In addition to
observation of design and safety instructions according to DIN EN 14986 and DIN EN 13463, the fan has to be assigned
exactly to the relevant degree of protection and labelled accordingly. The manufacturers have to prove conformity.
Areas with hazard of explosion exist in the chemical industry, in gasworks, coking plants, varnishing units, petrol stations,
sewage and wastewater treatment plants, laboratory systems etc.
Prerequisites of explosion are:
Flammable substances (such as gas, dust),
Oxygen in sufficient quantity of air
Ignition source (sparks, fire, hot surfaces, electrostatic discharges)
The following measures have to be taken if explosions cannot be excluded:
Prevention of explosible atmosphere
Avoidance of ignition sources
Moderation of damaging effects of explosions
An efficient and supervised ventilation system is often a sufficient measure for avoiding ignitable atmosphere and,
consequently, hazard of explosion.
Protection demands on a fan depend on the probability of occurrence of explosible atmosphere in the medium conveyed
or/and in the surrounding. Hazard is classified in three zones:
The plant operator or the relevant board of control has to decide which protection is necessary and which additional
regulations have to be considered. This means that the customer has to specify in the order which kind of protection the fan
has to have.
Fans VRE are supplied for the following types of ignition protection:
On principle, application in zone 0 is not possible. Gases of explosion group IIC (hydrogen excluded), gases with ignition
temperature below 200 °C, and combustible dusts are likewise impermissible.
Classification generally differentiates between inside (medium conveyed) and outside (surrounding). Every zone of hazard
requires its special design. Explosion-proof electrical devices (motors, switches etc.) and electrically conductive materials
(preferably conductive and flame retardant polypropylene --> PPsX) are employed. General classification is as follows:
Special demands for operation with frequency inverter
Motors with increased safety EEx e II must not be used in inverter operation. Motors EEx de with flameproof enclosure can
be employed in inverter mode if they are equipped with special winding protection (special design TS15). Standard motors
can be used and operated in inverter mode if the surrounding is not an EX zone and the fan meets certain design demands.
Radial fans of plastic materials
Series VRE
direct driven
Technical explanation
Explosions
Hazard
Avoidance of
Category
hazard
zone
ignition sources
acc. to ATEX
continuous
zone 0
even in the event of
1
long periods
rare incidents
likely
zone 1
even in the event of
2
to occur
frequent disturbances/faults
infrequently
zone 2
during normal operation
3
short period
MIETZSCH
Impeller/housing
inside
outside
designation
without inverter
with inverter
material
zone 2
zone 2
Z2Z2
EEx e II
EEx de
not conductive
zone 2
none
Z2Z3
EEx e II
standard
not conductive
zone 1
zone 1
Z1Z1
EEx e II
EEx de
conductive
zone 1 zone
2
Z1Z2 EEx e II EEx de conductive
Hazard zone
Motor
i_v
re_
en
(
09/
06)
t
emperature class T3 (ignition temperature of gas > 200 °C)
explosion group of gases IIB+H2 (IIA and H
2
included, IIC not included)
constructional safety
category (2G = gases of zone 1, 3G = gases of zone 2)
Equipment-group II (use in mining not permissible)
Zone 1:
II 2G c IIB+H2 T3
Zone 2:
II 3G c IIB+H2 T3
