Howden ELF - Page 22

Howden 24-07.030r04 22/25
E-series Axial Flow Cooling Fans
Service Manual
Problem
Possible cause
Possible solution
Vibration level high. (2)
Blades are out of tracking.
The blade tips should be
reasonably located in the
same plane. A maximum
tolerable deviation of 0.5%
of the fan diameter is ad-
vised.
Contact Howden for ad-
vise.
Fan is in stall.
Decrease blade angle or
replace impeller.
Resonance of the cooler
structure.
Change natural frequency
of the cooler or run the fan
at a different speed or
install a fan with more or
fewer blades.
Scratches or small dam-
ages.
Transport and handling.
We advise to fill these
cracks with a touch-up
material e.g. Sikaflex 252
to prevent moisture pene-
tration affecting the blades
(Contact Howden for a re-
pair kit).
Hairline cracks on blade
surface.
Could appear in resin rich
areas around the edges of
the fan blades and will
normally stop progressing.
Hairline cracks are harm-
less in itself, however we
advise to fill these cracks
with a touch-up material
e.g. Sikaflex 252 to pre-
vent moisture penetration
affecting the blades (Con-
tact Howden for a repair
kit).
Noise higher than pre-
dicted.
Airflow higher than speci-
fied.
Reduce blade angle.
Static pressure too high.
Fan too close to obstacles.
Contact Howden for ad-
vise.
Influence of mechanical
noise caused by drive-
train.
Contact drive-train sup-
plier.
Resonance of fan-drive
and/or support structure.
Contact Howden for ad-
vise.
Table 5