Flameproof motors | 27
www.weg.net
ATTENTION
An improper key can result in a
significant system unbalance, which
can cause the vibration to be above
acceptable limits.
If the key length exceeds the length of
the coupling hub the part extending
beyond the coupling hub must be
removed by machining to the shaft
diameter.
5.1.5.1 DIRECT COUPLING
Whenever possible, it is recommended to use
direct coupling due to lower cost, less space
required, no belt slippage and lower accident risk.
Also in cases where gear boxes are applied,
preference should be given to direct coupling.
ATTENTION
Always use flexible couplings; rigid
couplings require special bearing
arrangement as well as axial and radial
alignment of the shafts.
Figure 5-9 - Axial clearance of the coupling
ATTENTION
Align carefully the shaft ends using,
whenever
possible,
flexible
coupling, tolerating a minimum
clearance (Axial gap) of 3mm
between the couples as shown
Figure 5-9.
5.1.5.2 GEARBOX COUPLING
Poorly aligned gearbox couplings normally cause
jerking motions which provoke vibration to the
coupling and to the motor. Therefore, due care
must be given to correct shaft alignment, perfectly
parallel in cases of straight gears, and at the
correct angle for bevel or helical gears.
Perfect gear arrangements can be checked by
inserting a strip of paper on which the teeth marks
will be traced after a single rotation.
5.1.5.3 BELT AND PULLEY COUPLING
Belt transmission is the most commonly used when
a speed ratio is required.
The couplings used must be suitable to withstand
radial and axial vibrations during operation. Special
care must be taken to avoid that the allowable load
and speed limits given by the catalogs are not
exceeded.
ASSEMBLY OF PULLEYS:
the assembly of
pulleys on shafts featured with keyway and
threaded hole must be done by inserting it halfway
up to the keyway merely by manual pressure.
On shafts without threaded hole it is recommended
to heat up the pulley to about 80ºC (Figure 5-10).
Figure 5-10 - Assembly or pulleys
The couplings used must be suitable to withstand
radial and axial vibrations during operation. Special
care must be taken to avoid that the allowable load
and speed limits given by the catalogs are not
exceeded.
DISASSEMBLY OF PULLEYS:
for pulleys
disassembly it is recommended to use the devices
shown in Figure 5-11 in order not to damage the
key neither shaft surface.
Figure 5-11 - Disassembly of pulleys
Hammers should be avoided when fitting pulleys
and bearings. The fitting of bearings with the aid of
hammers causes spots in the bearing races. These
initially small spots increase with usage and can
develop to a stage that completely damages the
bearing. The correct positioning of a pulley is
shown in Figure 5-12.