6
ZerAx
®
axial flow fan types AZL-AZN-AZW
measurement. Operation close to the
stalling area produces poor results also.
6. Maintenance
6.1 Before maintenance
Switch off the power and
disconnect the motor cable in
the terminal box, before
beginning work on the rotor and motor.
For fans with PM motors, make sure the
motor axles cannot rotate during
service, e.g. by blocking the fan rotors.
PM motors can generate high voltages
when the motor axles rotate, even
though the power is disconnected.
6.2 Cleaning
Clean the fans at least quarterly. The
intervals may have to be adjusted,
dependent on the operation and
operational conditions. Corrosive and
dust filled atmospheres typically reduce
the intervals. Please note that deposits of
dust can be ignited by high surface
temperatures and constitute a safety
risk.
6.3 Vibration levels
Once the installation is complete and for
every 1,000 hours of operation the
vibration levels must be checked.
The vibration levels depend on
the installation and the fan
speed. Vibrations have great
effect on the fan life and efficiency.
Measure the levels at operational fan
speed, radially at two points with a 90°
offset and at the free shaft end of the
motor. The levels must be within the
below limits.
Vibration level limits at startup
• Motors up to 37 kW
- less than 6.3 mm/s
• Motors over 37 kW
- less than 4.5 mm/s
Fans that exceed the limits usually
require cleaning or balancing of the
rotors. Alternatively, the causes must be
investigated and removed. Refer to ISO
14694.
For variable speed fans the vibration
level limits are likely to be exceeded at
certain speeds. Continuous operation at
these speeds must be avoided.
6.4 Fan casings
The fan casings require no other
maintenance than ordinary cleaning.
Check painted casings regularly and
keep them in good condition.
6.5 Rotors
The rotors are carefully balanced and the
rotor blades are set at precise angles in
the production. The rotors are thereby
optimised for vibration free operation at
the desired operation point with regard
to pressure, airflow and fan speed.
Vibrations that occur in operation may
be due to accumulation of dust and dirt
on the hubs and blades. If vibrations
persist after cleaning, expert assistance
should be called for immediately.
Continued operation with vibrations
shorten the life of the fan and motor
bearings.
6.6 Motors
Refer to the motor manufacturer’s
documentation and the nameplates for
how to service the motors.
Motor maintenance
• Inspect the motor for wear signs
and damaged parts.
• Clean the motor casing, motor
cooling fan and motor shell.
• Drain the motor of condensed
water.
• Check supply cables and electric
connections for impairments.
• Check terminal box seals and cable
glands.
• Lubricate bearings
Refer to the motor manual for
service information such as
lubrication intervals, grease
amounts, when to replace bearings
etc.
-
Permanent magnet motors
are
lifetime lubricated. Bearings may,
however, need replacement.
-
AC motors
up to size 132 have
lifetime-lubricated bearings.
Motor sizes 160 to 280 require
lubrication according to the
manufacturer’s instructions.
Fans with motor sizes 225 to 280
have nipples on the outer fan
casings. For fans with motor sizes
160 to 200, nipples on the outer
fan casings are optional.
Refer to the motor nameplates for
recommended grease type,
amount and interval.
Use a manual grease gun
for lubrication.
Excess grease causes
bearings to overheat and results
in failure.
Motor
size
Poles
Lubrication
Grease
amount
[g]
50 Hz
60 Hz
160
2
22000 20000
13
4
25000 25000
6
8
180
2
17000 14000
18
4
25000 25000
6
8
200
2
15000 12000
21
4
25000 25000
6
8
225
250
280
2
5000
4000
27
4
14000 12000
6
20000 17000
8
24000 20000
2
4000
4000
34
4
13000 10000
6
18000 16000
8
20000 20000
Table 5.
Grease amounts and intervals for
WEG W22 TEFC motors – ball
bearings
Motor
size
Poles
Lubrication
Grease
amount
[g]
50 Hz
60 Hz
160
2
16000 12000
13
4
25000 25000
6
8
180
2
11000 8000
18
4
25000 25000
6
8
Table 6.
Grease amounts and intervals for
WEG W22 TEFC motors – roller
bearings
