CENTRIFUGAL TYPE
FANS
IMPORTANT:-
Before erection and
starting of the fan the following procedure should be followed. Failure to
observe these instructions may lead to a fan bearing seizure or damage to
the motor.
1. Ensure that the shaft and bearings have not become misaligned
in transit.
2. In the case of grease lubricated ball/roller bearings check
that the lubrication is satisfactory.
3. When a fan set is inoperative it is recommended that the
bearing lubrication be checked and that both fan and motor shafts be rotated
by hand about every 10 days to prevent damage to bearings.
4. ROTATION: Check the instructions on the motor nameplate and
check that the fan rotation is correct as shown by the direction arrow on
the fan casing. Reverse rotation with radial and forward curved bladed
impellers will give reduced performance and power consumption but can cause
severe overloading of the motor in the case of backward bladed impellers.
ERECTION:-
When installing a fan the foundation should be checked to ensure that it is
firm and even. Avoid stain on the fan casing by tightening the foundation
bolts a few turns each in rotation. The fan shaft should be perfectly
level. Shafts and bearings should be checked for correct alignment.
Standard Fans fitted with a bearing in the inlet should not operate at air
temperature above 80’C (176’F). The inlet ducting should be an easy fit so
that no strain is placed on the fan that would affect the bearing. It may
also be necessary to provide an access door in the ducting close to the fan
inlet to facilitate bearing maintenance and lubrication.
All other standard fans should not operate at temperatures above 100’C
(212’F). When ordering replacements please quote serial number and in all
cases of bearings, the shaft diameter.
VEE BELTS:-
If the fan is driven through vee belts, the pulleys must be correctly
aligned and the best tensioned in accordance with the drive manufacturers
instructions. Position the pulleys near to the fan and motor bearings in
order to keep the load imposed by the tension of the bee belts to a
minimum. Where keyless taper bushed pulleys are used, the protective grease
film should be removed from the bore and outside surface of the bush, also
from the tapered bore of the pulley. The grub screws in the bush should be
tightened gradually and alternatively until all are pulled up very tightly.
The belts should be inspected from time to time and any slackness taken up
by moving the position of the motor on the slide by means of tension
screws. Under average conditions the majority of stretch takes place in vee
belts during the first few days under load. It is therefore recommended
that newly installed vee belts be examined and the tension increased if
necessary after the first few days under load and thereafter as required.
Excessive wear on the sides of the vee belt means misalignment of the
pulleys and this should be rectified at once. New and used vee belts should
not be run together in the same set and vee belts of different types and
brands should not be mixed. Always fit all new or used matched vee belts in
the same set.
Extra care during the first few hours of operation will result in efficient
and long vee belt life.
GENERAL MAINTENANCE FOR BALL AND ROLLER BEARINGS:-
Ball or roller
bearings are of the self-aligning plummer block type incorporating either
single row deep groove ball bearings or double row ball/spherical roller
bearings and are complete with seals against the ingress of dust. They are
initially charged with grease when assembled. A grease nipple is fitted to
the sealed units incorporating the deep groove ball bearing to enable
re-greasing if considered necessary (normally no more than once a year). A
good quality lithium base grease should be used.
Fans fitted with
plummer blocks incorporating double row self-aligning ball bearings or
spherical roller bearings are suitably packed with grease on assembly. Free
space in the plummer block should only be partly filled with grease
(approximately 40%) since over filling can cause over heating of the
bearing.
The re-greasing
interval for these bearings is dependent on type, size, speed, operating
temperature and grease.
Further information
can be obtained from our sales office.
The manufacturers
reserve the right to alter specification without prior notice.
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AXIAL FLOW &
BIFURCATED FANS
GENERAL INFORMATION:-
Under normal
circumstances handling clean air, axial fans will require cleaning only
about once a year. However, the fan and system should be checked at regular
intervals to detect any unusual accumulation.
On externally motor
driven axial fans the impeller should be specially checked for build-up of
material or dirt which may cause an imbalance with resulting undue wear on
bearings and v-belt drives. A regular maintenance programme must be
established as needed to prevent this build up.
Regular inspection of
the rotating assembly should be made to detect any indication of weakening
of the impeller because of corrosion, erosion or metal fatigue, etc.
Do not attempt any
maintenance on a fan unless the electrical supply had been completely
disconnected. If an isolating switch has not been provided, remove all
fuses from the circuit and lock the fuse panel so that they cannot be
accidentally replaced.
Where guards have to
be removed to carry out maintenance or servicing of equipment these must be
correctly replaced and the fastenings checked.
I. DIRECT ON LINE STARTING:-
This starting method
is normally used with the smaller type of Motor. It is so called because
the electric current required to start the fan is taken as an instantaneous
surge by the motor, this is known as ‘Starting Current’. This ‘current draw’
can sometimes equal as much as eight times the running current of the motor
(which is shown the motor nameplate). Therefore, care should be taken in
the selection of this type of starting method.
II. STAR DELTA STARTING:-
This starting method
is normally for larger power units or where ‘current draw’ on the Direct on
Line method would exceed the available supply. The ‘current draw’ could
with this method be 2/3 times the rating of the motor, bit the load would
not be instantaneous, since the ‘current draw’ would be split over the Star
Delta cycle. If there is any doubt as to the starting method to use for
your particular application please consult the electricity authority or the
supplier of the fan equipment.
Wherever possible the
impeller should be rotated by hand before the fan is fitted into the
ductwork system and before it is ‘switched on’ electrically.
On Reversible Fans,
care must be taken to ensure that the Impeller has stopped rotating before
it is reversed.
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