ZerAx
®
axial flow fan types AZL-AZN-AZW
5
The rotor must be completely
stationary, before restart of the fan for
directional change of rotation. It is
recommended to install a time delay
for this purpose.
Check that the rotational direction of the
rotor complies with the arrow on the
outside of the fan casing. Flick the fan
power briefly On, then Off. If the
direction is wrong, disconnect the main
power supply and check the
connections.
5. Start of operation
Fans fitted with frequency converters
must have the control unit set up, before
start of operation. Refer to the Novenco
document “Configuration of frequency
converters for Novenco fans”.
Perform the below steps every time the
fans have been stopped.
5.1 Before startup
Check the fans and installation location
in accordance to the below checklist and
correct and improve as necessary.
Checklist
•
Safe operation
The blade clearance must be
minimum 0.1x motor shaft
diameter (min. 2 mm, max. 13 mm)
all around the rotor circumference.
The axial distance between the
rotor hub and stator must be min.
3.5 mm.
Wire guards should be mounted on
the inlet and outlet sides.
•
Transportation rods
Fans on support frames and with
vibration dampers have
transportation rods in the support
frames, which must be removed
before start of operation. The
handles are marked with a strong
colour.
•
Clean ducts
The fans and duct connections must
be clean and free from tools and
objects that can affect the airflow.
•
Electric connections
The electric connections must be
correct and in accordance to the
prescribed requirements. Flick the
fan power briefly On, then Off, to
check the rotational direction of the
rotor.
5.2 Motors with Y/
Δ−
start
Set the relay for start of the fans to the
Startup time from the technical
specifications from the AirBox program.
Alternatively, calculate the value with
the below formula.
Calculation of startup time
The motor torque can vary within the
below limits and affect the startup time.
5.3 Startup procedure
Refer to the motor manual and the
AirBox technical specifications for
specific information and procedures.
Startup procedure
1. Start the fan.
2. Check that no abnormal noises are
present.
3. Check that the vibration levels are
acceptable.
See section “6.3 Vibration levels”.
4. Check that the fan operates normally
after 30 minutes of operation.
The fans are designed for
continuous operation. The
below kinds of operation may
cause fatigue breaks in the rotors and
endanger people.
•
Operation in stall area, i.e. with
counter pressure that pulsates -
called pump mode
•
Operation with uninterrupted
and repeated starts and stops
•
Uneven flow velocity through
fans
Ask Novenco if in doubt.
5.4 Air volumes for free inlet fans
For fans with measuring pipes and free
inlets, the air volume can be calculated as
shown below. The measuring pipes are
optional accessories and fitted close to
the fan inlet.
The below formula gives the air volume
in m
3
/s. Multiply by 3,600 to convert to
m
3
/h, or by 2188.88 to convert from
m
3
/s to CFM.
Free inlet cones are integrated on the
AZL and is an accessory for the AZN and
AZW.
The suction must be directly from the
suction chamber.
Fans with low blade angles can make
noise at high pressures, which affects the
t
s
=
t
s
: Startup time [s]
P
: Rated output of motor [kW]
P
v
: Required power of fan [kW]
n
: Fan speed [RPM]
:
Ratio between the start and
the nominal motor torque
:
Ratio between maximum and
nominal motor torque
I
v
: Polar moment of inertia for fan
[kgm
2
]
I
m
: Polar moment of inertia for
motor [kgm
2
]
M
s
: -15% to +25% of catalogue
value
M
k
: -10% to 0% of catalogue value
0.24 n
2
I
m
I
v
+
(
)
×
×
10
4
P
M
s
M
-------
M
k
M
--------
P
v
P
------
–
+
×
×
-----------------------------------------------------------------
M
s
M
-------
M
k
M
--------
Figure 12.
Measurement of pressure
difference
q
=
q
: Air volume [m
3
/s]
k
: A constant, see table 4.
dps
: Difference between p
away
and
p
fan
[Pa]
p
fan
: Static pressure at fan inlet [Pa]
p
away
: Static pressure away from fan
[Pa]
Fan
sizes
Constant,
k
Fan
sizes
Constant,
k
250/160
0.0510
900/350
0.7204
280/160
0.0694
1000/350
0.9001
315/160
0.0917
1120/350
1.2019
355/160
0.1183
1250/350
1.5636
400/160
0.1502
1000/560
0.871
450/160
0.1894
1120/560
1.129
500/160
0.2343
1250/560
1.441
500/350
0.1921
1400/560
1.844
560/350
0.2537
1600/560
2.453
630/350
0.3324
1800/560
3.142
710/350
0.4329
2000/560
3.913
800/350
0.5603
Table 4.
Constants for air volumes
paway
pfan
k
dps
×
