IOM – FLEXY II – 1007 – E Page 35
The actual res is t anc e of duct work systems is not alway s identical to the calculated theoretical values. To rectify this, it may be
necessary to modify the pulley and belt setting. To this effect, the motors are fitted with v ariable pulleys.
SITE TEST AND MAINTEN ANCE
Measure the motor absorbed power.
If the absorbed power is great er and t he pres s ure lower t han t he rat ed v alues, the v entilat ion sy s t em has a lower pres s ure
drop than anticipated. Reduce the flow by reducing the rpm. If the system resistance is signif icantly lower than design, there is
a risk that the motor will ov erheat resulting in an emergency cut out.
If the absorbed power is lower and the pressure great er t han the rat ed v alues , y our system has a higher pressure drop t han
anticipated. Increase the flow by increasing the rpm. At the same time you will increase the absorbed power which may result
in hav ing to increase the motor size.
To c arry out t he adjus tm ent and to av oid a t im e-consuming re-st art, stop t he m ac hine and if necessary loc k t he m ain switc h.
First unscrew the 4 Allen screw(s) on the pulley (see f igure 13).
Actual diameter (DM) or distance between faces for a giv en number of
turns from f ully closed wit h SP A b e l t i n (m m )
Pulley
ty pe
Pulley
External
Diameter
Min
Dia /
Min
Dist
Max
Dia /
Max
Dist
Nb of turns
from fully
closed to
fully open
0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5
95 116 5 114 112 110 108 106 103 101.3
99.2
97.1
95 -
8450 /
D8450
120
20.2 28 5 21 21.8
22.5
23.3
24.1
24.9
25.7 26.4
27.2
28 -
110 131 5 129 127 125 123 121 118 116 114 112 110
-
8550 /
D8550
136
20.6 31.2 5 21.6
22.7
23.8
24.8
25.9
26.9
28 29.1
30.1
31 -
Table_1
The easies t way to determ ine the f an rot at ion s peed is to
use a Tachometer. If not available the f an rpm can be
estimated using the following two methods.
1
st
Method wit h t he pulley secured in place
:
Meas ure t he distanc e between t he two out s ide f aces of t he
pulley.
Using table (1) the motor pulley actual diameter can be
estimated.
L
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