4
mm/s, rms*, is not allowed in case of
position on feet or anti-vibration
mountings.
* ISO 2954, Requirements for instruments
for measuring vibration severity.
After thirty minutes of operation check that
the fan operates normally.
6. Maintenance
6.1 Prior to maintenance
When the fan is out of operation for reasons
of inspection or repair/maintenance, the
electric system must be switched off and
protected so that the fan is not cut in
unintentionally.
6.2 Fan casing
The fan casing requires as standard no
maintenance other than ordinary cleaning.
If the fan casing is painted, the painted
surface should be checked regularly and
repaired where necessary.
6.3 Impeller
The impeller (rotor unit) is supplied from
the factory with the blades adjusted to the
pitch corresponding to the desired
operating point (pressure and airflow) at
the fan speed in question. To ensure
vibration-free operation the impeller has
been carefully balanced in this position.
Vibrations occurring during operation will
normally be due to accumulations of dust
or dirt on hub and blades, and will
disappear after cleaning. Should this not be
the case, expert assistance should be called
in immediately, as continued vibrations
will shorten the life of the blades and the
motor bearings.
6.4 Motor
The motor normally only requires
maintenance of the bearings as indicated in
the maintenance instructions for electric
motors.
6.5 Dismounting of motor
Prior to commencing the work, switch off
the current and disconnect the motor cable.
Next, dismount any ducts and
downstream guide vane arrangement (fig.
7, items 13, 10, 11, and 14) on the fan outlet
side.
Remove the impeller centre screw (item 09)
and centre disc (item 08).
Dismount the impeller by means of a puller
fastened in the two threaded holes of the
hub boss (item 12).
Detach the motor by loosening the screws
in the motor shell (items 05 and 06). Now
the motor (item 01) and motor flange (item
02) can be removed.
In dismounting and disassembling the fan
be careful not to expose the individual
parts to shocks etc. likely to damage the
motor bearings or other fan components.
6.6 Mounting of motor
After servicing remount the motor, check
that the motor flange (fig. 7, item 02) is
correctly located and that the motor shaft is
concentrically placed in the fan casing,
before tightening the bolts (item 06).
Mount the impeller (item 07) on the motor
shaft by means of a tool fastened in the
threaded hole of the motor shaft. Fix the
impeller hub to rest against the motor shaft
collar.
Check that the mean blade clearance is
within the minimum allowable value. See
section “ 4.1 Prior to installation” for values
and calculation of mean blade clearance.
Now mount the centre screw (item 09) and
centre disc (item 08). Replace lock washers
and lock nuts during fan assembly. Finally,
connect the motor cable in the terminal box
(item 01) and any ducts and downstream
guide vane arrangement (item 13).
To start the fan follow the procedure
described in section “ 5. Start of operation”.
6.7 Blade pitch adjustment
The blade pitch has been adjusted in the
factory with a special tool (fixture) to
deliver the performance required by the
customer/order on delivery.
If the fan performance is required to be
changed it is possible to change the blade
pitch. It requires knowledge of the motor
load and the max. permissible blade pitch
on the graph as related to the motor rating
(in case of blade pitch increase).
Contact Novenco before any such
adjustment of the blade pitch.
Novenco can supply special tools for blade
pitch adjustment and instructions for
impeller balancing.
The brochure "Blade-angle tool" is
available on request.
6.8 Troubleshooting
These are likely causes of breakdowns/
failures.
Deficiency in performance
Blocked air supply to the fan inlet side
– Damper closed
– Duct choked
– Supply fan, if any, stopped
– Motor defective
– Motor cut out
– Wrong direction of rotation of impeller.
Noise/vibrations
– Bearings in electric motor defective
– Impeller out of balance
– Impeller worn/damaged
– Bolts/components loose
– Impeller blades have different pitch
angles
– Fan operates in the stalling area. May
result in break-down - repair failures,
see "Deficiency in performance".
7. Sound
The sound generation of the fans
depends on installation and operating
conditions, which means that no general
data of the sound generation can be
given.
Reference is made to our catalogues or
computer programs for calculation of the
specific sound generation.
Important:
The fan is designed for
continuous operation. The
following kinds of
operation may cause fatigue
break in the impeller and
endanger people.
- Operation in stall area
- Operation with pulsating
counter pressure - called
pump mode
- Operation with repeated
starting and stopping
If in doubt Novenco should
be contacted to assess the
suitability of the fan.
