Flexible Couplings; Types Of Misalignment; Coupling Alignment; Angular Misalignment - ITT MARLOW Serie Manual De Instalación, Operación, Mantenimiento

C. MOTOR BEARING LUBRICATION:
Follow motor manufacturer's specifi cations.

FLEXIBLE COUPLINGS

A fl exible coupling should not be used to compensate for
misalignment of the pump and driver shafts. The purpose
of the fl exible coupling is to compensate for temperature
changes and to permit end movement of the shafts with-
out interference with each other while transmitting power
from the driver to the pump.

TYPES OF MISALIGNMENT

There are two forms of misalignment between the pump
shaft and the driver shaft, as follows:
Angular Misalignment – Shafts with axes concentric
but not parallel.
Parallel Misalignment – Shafts with axes parallel but
not concentric.

COUPLING ALIGNMENT

The faces of the coupling halves should be spaced far
enough apart so that they cannot strike each other when
the driver rotor is moved hard over toward the pump.
Due allowance should be made for wear of the thrust
bearings. A minimum dimension for the separation of the
coupling halves is specifi ed by the manufacturer, usually
/ ". The necessary tools for approximately checking the
1
8
alignment of a fl exible coupling are a straight edge and a
taper gauge or a set of feeler gauges.
ANGULAR ALIGNMENT
A check for angular alignment is made by inserting the
taper gauge or feelers at four points between the coupling
faces and comparing the distance between the faces of
four points spaced at 90º intervals around the coupling.
The unit will be in angular alignment when the measure-
ments show that the coupling faces are the same distance
apart at all points.
PARALLEL ALIGNMENT
A check for parallel alignment is made by placing a
straight edge across both coupling rims at the top, bottom
and at both sides. The unit will be in parallel alignment
when the straight edge rests evenly on the coupling rim at
all positions. Allowance may be necessary for temperature
changes and for coupling halves that are not of the same
outside diameter. Care must be taken to have the straight
edge parallel to the axis of the shafts. Angular and parallel
misalignment are corrected by means of shims under the
motor mounting feet. After each change, it is necessary to
recheck the alignment of the coupling halves. Adjustment
in one direction may disturb adjustments already made in
another direction. It should not be necessary to adjust the
shims under the pump.

GROUTING

When the alignment is correct, the foundation bolts
should be tightened evenly but not too fi rmly. The unit
can then be grouted to the foundation. The base plate
should be completely fi lled with grout and it is desirable
to grout the leveling pieces, shims or wedges in place.
Foundation bolts should not be fully tightened until the
grout is hardened, usually about 48 hours after pouring.
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FINAL CHECK OF ALIGNMENT

After the grout has set and the foundation bolts have
been properly tightened, the unit should be checked for
parallel and angular alignment and, if necessary, correc-
tive measures taken. After the piping of the unit has been
connected, the alignment should be again checked.

"V" BELT ALIGNMENT

Although alignment is not as critical in V-belt drives as
in others, proper alignment is essential for long belt and
sheave life. First, make sure that drive shafts are paral-
lel. The most common causes of misalignment are non-
parallel shafts and improperly located sheaves. Where
shafts are not parallel, belts on one side are drawn tighter
and pull more than their share of the load. As a result,
these belts wear out faster, requiring the entire set to be
replaced before it has given maximum service. If mis-
alignment is in the sheave, belts will enter and leave the
grooves at an angle, causing excessive belt cover and
sheave wear.

CHECK SHEAVE MOUNTING AND ALIGNMENT

"V"-Belt drives do not require alignment to as close toler-
ances as most other types of drives – but unless the belts
enter and leave the sheaves in a relatively straight line,
wear is accelerated.
Steel
Straight
Edge
Note gap
between
Steel
Straight
Edge and
sheave
(A)
The two most common causes of misalignment are
shown: (a) the shafts of the driver and driven machines
are not parallel, and (b) the sheaves are not located
properly on the shafts. To check alignment, all you need
is a straight-edge or, for drives with longer centers, a steel
tape. If these aren't available, you can, as a last resort,
even use heavy string. Just line the straight edge or tape
along the outside face of both sheaves as shown in the il-
lustration. Misalignment will show up as a gap in between
the sheave face and straight-edge, or perhaps as a "break"
in the tape or string. Make sure that the width of the
outside land is equal on both sheaves, when using this
method.
Note gap
between
Steel
Straight
Edge and
sheave
Steel
Straight
Edge
(B)