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The correct tension of Novenco's stand-
ard belts are in table 3, defined as the ra-
tio between the deflection of the belts de-
pending on the pressure, the shaft dis-
tance between the belt pulleys and the
diameter of the smallest pulley (see fig.
4).
Figure 4. Belt tension
Normal
Diameter
tension,
Belt
of smallest
P, for
pulley
each
profile
[mm]
belt
[N]
>71 < 90
XPZ
>90 < 125
25
>125
>100 < 140
SPA
>140 < 200
50
>200
>160 < 224
SPB
>224 < 355
75
>355
>160 < 224
XPB
>224 < 355
75
>355
>250 < 355
SPC
>355 < 560
125
>560
Table 3. Standard belt tension
A tension meter is recommended as ex-
act measuring instrument, see fig.5.
Figure 5. Tension meter
After tension of the belts the motor is fas-
tened.
After that the fan is started as described
in section 5. Start of operation.
6.6 Belt pulleys
When changing the belt pulley to anoth-
er size - i. e. changed fan speed - it must
be checked that the speed does not ex-
ceed the max. permissible speed which is
stated on the nameplate of the fan and
that the motor rating is sufficient for the
changed power consumption.
The belt drive must be dimensioned hav-
ing regard to the smallest permissible
belt pulley diameter according to in-
structions from the supplier.
All belt pulleys assembled at the factory
are provided with a TAPER-LOCK bush.
Removal and mounting of belt pulley
(fig. 6)
Do not use hammer for removal or
mounting of belt pulleys as even light
blows and strokes might damage the
bearings resulting in noise from bearing
and quick wearing.
Belt
deflection
per
100 mm
shaft
distance
[mm]
1,95
1,80
1,70
2,75
2,55
2,45
2,55
2,22
2,15
2,20
1,85
Figure 6. Belt pulley
1,75
Removal
2,55
2,20
1 Remove and lubricate the screws (14)
2,00
slightly with oil and place one of them
in the threaded hole of the bush (15).
2 Turn the screw so the bush is loosened
from the hub of the pulley and the
unit is loosened from the shaft.
3 Pull the belt pulley and bush off the
shaft end as one unit.
Mounting
1 Clean the hole of the pulley and the
inner and outer side of the bush for
rust-preventative and check that the
surfaces are totally clean.
2 Lubricate the screws slightly with oil
and place them loosely in the
threaded holes (14).
3 Clean the shaft and push the pulley
and bush unit back onto the shaft.
4 Tighten the screws one after another
until they are firmly tightened.
5 Mounting and adjustment of belts:
See section 6.5 'Belt change and
adjustment'.
6.7 Bearing assembly
The belt driven fans are provided with a
bearing assembly. The construction of
the bearing assembly varies according to
fan size and type so when changing a
bearing assembly follow one of the be-
low procedures depending on size and
type of fan.
After mounting of new bearings the im-
peller must be carefully centred in rela-
tion to the inlet cone.
CNA & CNA-M, 250-500/R and
CNB & CNB-M, 400/R (See fig. 7)
The bearing assembly consists of bearing
tube, ball bearings and shaft which is
mounted on a conical cover in the back
plate of the fan. The bearings are in dust
and water-tight enclosures and cannot
be re-greased. However, in special cases
the bearing housings can be changed so
that re-greasing can take place.
When the bearings are worn the whole
bearing assembly is replaced. First re-
move belt guard, V-belts and fan belt
pulley, then remove the conical cover
with bearing assembly and impeller and
at last remove impeller and bearing as-
sembly.
Figure 7. CNA 250-500/R and CNB 400/R
CNA & CNA-M, 630-1000/R (See fig. 8)
The bearing assembly consists of two
flange single-bearings (FY) and shaft
where each flange bearing is mounted on
a conical cover which is mounted in the
back plate of the fan. The bearings are in
dust and water-tight enclosures and can-
not be re-greased. In particularly ex-
posed cases the bearing housings can be
provided with a grease nipple so that re-
greasing can be made.
When replacing bearings first remove
belt guard, V-belts and fan belt pulley.
Then remove the conical covers with
bearing assembly and impeller. The im-
peller is withdrawn from the shaft after
which the internal hexagon-headed
3
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