Cod. 985719 – 00 / July 2004
9
3.2.3. Operating temperature
The standard operating temperature is indicated in the catalogues. For short periods it is possible to use the fan at a
temperature lower than –20°C, but it is dangerous to start a fan which was standing at a temperature lower than –20°C.
For special application please contact our “Technical Department”.
For use at temperatures higher than those indicated in the catalogue, the limit is controlled by the bearing grease; in this
case please refer to the paragraph “Maintenance”.
The operating temperature (airflow, ambient temperature) and the temperature class for the fans in ATEX version are
indicated in the rating plate.
3.3. BALANCING
The fan impellers are statically and dynamically balanced with grade G4 according to ISO 1940.
3.4. BEARINGS
In the “Maintenance” chapter are listed the bearings used on each fan.
3.4.1. Bearing life
The Nicotra bearings have been selected to achieve a bearing life L
10h
of 40.000 hrs according to ISO 281. This value is
calculated with common pulley sizes (see also the chapter “Pulley selection”) and at maximum load. In more common
load conditions, the bearing life can easily exceed this value.
If the bearing life depends on the applied loads, these are due to many factors; the most important is the belt tension
which is function of the installed power, pulleys diameter and number of grooves.
In the catalogue tables are listed the minimum diameter of the pulleys and the maximum number of grooves suggested in
order to respect the maximum permissible loads.
The belt tension must never be higher than the values calculated in the selection program “Ventil”.
3.5. SHAFTS
Shafts diameters are selected to have a critical speed higher than the maximum permissible speed with a safety factor
≥1.2.
4. INSTALLATION
Correct installation of the fan will ensure correct operation and avoid problems in the future.
Atex fans, must never be installed in presence of an explosive atmosphere. If they are connected to other components or
machines, such as motors, drive elements (pulleys, belts, couplings…) etc, these must also be Atex compliant and not
change the mechanical characteristics of the fan in such a way that the fan can not remain Atex compliant according to
the standard described in the paragraph 1.1.
The fan must always be connected to an earth cable. Category 2 fans have an earth screw, while for category 3 fans it is
necessary to connect an earth cable to the housing.
The painted frames can not guarantee a superficial resistivity lower than 1 Giga-Ohm, so are not suitable as earth
connection elements.
4.1. FIXING THE FAN
Pay attention to the following points:
• the fan must be fixed to a base or to a rigid frame designed to avoid vibrations and resonance
• use all the fixing points and verify that the frame or the feet will rest on the whole surface
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