DEFECTS

CAUSES

POSSIBLE REMEDIES

Insufficient air delivery

1) Clogged piping and/ or obstructed
suction points.
2) Insufficient rotational speed.
3) Working pressure higher than design.
4) Clogged wheel.
5) Reversed rotation direction.
6) Overloaded filter.
7) Suction vorticity in the same rotation direction as the wheel.
8) Changes in section, sharp and close. Sudden expansions or curves not allowing the normal reset of the inlet dynamic pressure.

1) Clean pipings and hoods; check the position of locks.
2) Check the power voltage and the connection of motor terminals; check the gear ratio and that belts do not slip.
3) Design error. Replace motor and pulleys; replace and/or adapt the circuit.
4) Clean the wheel through the special door when the machine is stopped.
5) Check the connection of windings on motor terminal board.
6) Increase the operating frequency of the automatic cleaning device (where foreseen) or operate manually.
7) Fit an anti-turbulence device (straightening blades).
8) Check the layout of the air circuit.

 

Difficult starting.

9) Excessive power absorption.
10) Reduced power voltage.
11) Insufficient motor pickup torque.
12) Fuses not suitable for actual needs.
13) Inadequate evaluation of the fan inertia and of the fining components.

9) Like above.
10) Check the motor plate data.
11) Replace with a more powerful motor or, for radial fans, close the locks until reaching full speed.
12) Replace them.
13) Recalculate the moments of inertia and, if necessary, equip the fan with a new motor drive.

Insufficient pressure

14) Too much low rotational speed.
15)  Capacity higher than design values because of an error in the circuit dimen-sioning or of air temperature significantly different from the 15°C reference value.
16) Reversed rotation direction.
17) Wheel partially blocked and/or damaged.

14) Like above.
15) Change the gear ratio and/or replace the fan, redimension the circuit,
16) Like above.
17) Check the wheel assembly position, conditions.

Excessive air capacity.

(If rotational speed is correct, high ab-sorption for radial fans with curved blades
forwards)..

18) Rotational speed.
19) Air leaks through access doors, pipings, wrong-manufactured or wrong-installed components, or by-pass locks not closed properly.
20) Excessive evaluation of circuit power losses.

18) Check the rotation direction; the particular conditions of suction turbulence; rotational speed in the a.c. motor; power voltage and winding faults.
19) Check the system and replace the non complying components.
20) Close the locks or slow the speed down the desired performance.

 

Vibrations

21) Inadequate support structure (natural frequency close to the one corresponding to the fan rotational speed).

21) Alter the support adding some weight.

Absorbed power higher

than plate data.

22) High rotational speed so to require a higher power than the installed one.
23) Air density higher than design data.
24) Capacity higher than design levels for a pressure lower than design value.

22) Replace motor and pulleys and/or redefine the system.
23) Like above.
24) Like above.

Excessive noise

25) High number of revolutions to get the
required performance.
26) Failure in bearings.
27) Wheel unbalance and its sliding on the box.
28) Eccentricity between rotor and stator.
29) Vibrations in the winding.
30) Squilibri delle parti rotanti.

25) Use soundproof boxes and/or silencers; choose a bigger machine
with the same performances or a machine with lower rim speed.
26) Check the wear of bearings (in particular the proof ones) and lubrication.
27) Check the assembly positions of wheel and pipings.
28) Check the concentricity.
29) Can be reduced with higher quality motors.
30) Recheck the balance.

Air pulsations

31) Centrifugal fans operating under
conditions of zero capacity.
32) Instability of the suction flow with
presence of vortex.
33) Detachment of the fluid vein from the back of the blade or the walls of a pipe.

31) Redefine the inlet by the introduction of flaps.
32) Redefine the system and/or replace the fan.
33) Like above