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9 - FANS AND AIR DUCTS
Pulley and belt calibration
Attention: Before performing these operations, it is
necessary to verify that the unit is disconnected from
mains.
The centrifugal motorfans are coupled through pulleys and belts.
In these fans, the following must be taken into consideration:
Pulley alignment:
■ The pulleys must be on the same plane, so it is important to
check them with the help of a ruler or a laser aligner.
■ In case they are not aligned, remove the pulley screws, and
after removing the taper pin, the set of pulley and taper can be
slided over the axis (this action can be performed both in the
motor as well as in the fan).
Pulleys must stay on the same plane
Tensor
screw
Pulley
screws
Belt tension:
After fi xing the pulleys on the same plane, the belt tension is made
by tightening the tensor screw.
Excessive tension on the belt can lead to premature wear on the
assembly. Insuffi cient belt tension can cause slippage, overheating
and premature wear of the belt.
It is essential to tension the belts using the "Defl ection test"
described below:
■ The belt tension must be checked and corrected using a suitable
measuring instrument (tensiometer or dynamometer).
■ "Ea" calculation:
- Ea = (e x E)/100 = deformation in mm for a pulley centre
distance of 100 mm
34
- e = pulley centre distance in mm
- E = see table below for the value
- f = force applied
■ At the centre of the centre distance "e", apply a force "f", as
determined in the table below, to each belt. Set the belt tension
to obtain the calculated defl ection "Ea".
9.4 - Air ducts connections
The air supply and return ducts must be calculated in accordance
with the nominal fl ow and the unit's available pressure (refer to
the technical characteristics table).
The duct calculation and design must be made by qualifi ed technical
personnel.
It is advisable to take into consideration the following
Taper pin
recommendations:
■ Curves in the fan supply outlet(s) must be avoided. It is
recommendable to have a straight section of duct measuring
approximately 1 metre. If it is not possible, they must be as
smooth as possible, using indoor defl ectors when the duct is
of large dimensions.
■ When making the ducts, direction sharp changes must be
avoided since they can generate occasional pressure drops,
which aff ect the available pressure and the fl ow. The location
of discharge and aspiration grilles must be studied carefully to
avoid the air recirculation and the transmission and generation
of noises to the interior.
■ Consideration should be given to the need to install fi lters on
the return ducts, taking into account any particles in suspension
existing which could settle inside the machine (e.g. textile
fi bres).
■ Flexible connections must be made between the ducts and the
unit that avoid the noise and vibration transmission.
■ No matter the type of ducts used, they must be isolated and
not be composed of materials that propagate fi re nor expel
toxic gases in the event of a fi re. The internal surfaces must
be smooth and should not pollute the air that circulates within
them. In any case, the eff ective legislation about this issue
must be respected.
Belt type
f(N)
SPZ
25
Load to be applied per belt f (N)
Small pulley diameter (mm)
Belt deformation for a pulley centre distance of 100 mm - E (mm)
Important: During commissioning, the belt tension must
be checked after 48 hours of operation.
The belt tension must be checked in all cases and before
system start-up.
d (mm)
E (mm)
56 ≤ 71
2.45
< 71 ≤ 90
2.20
< 90 ≤ 125
2.05
125
1.90
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