Saturday, September 13, 2008

Coupling Alignment

Coupling Alignment
Good service life of the pump and driver
depends upon good alignment through the
flexible coupling. If the electric motor was
mounted at the factory, the pump and motor
were in alignment when shipped.

The alignment between the pump and driver should be inspected after installation to ensure that transportation or other handling has not caused misalignment of the unit.

Poor alignment may cause failure of the coupling, pump, motor, or bearings.

Alignment must not be attempted until the base is in position and the mounting and flange bolts have been tightened.

The recommended procedure for coupling
alignment is with the use of a dial indicator,
as illustrated in Figures 1 and 2.

The dial indicator is attached to one coupling halfwith the indicator button resting on the O.D. of the other coupling half to measure offset HALCO 1780 “W” Maintenance Page 3 misalignment.

To measure angular misalignment, the indicator is positioned so that the buttons rest on the face, near the O.D., of the other coupling half.

Rotate the shaft and dial indicator one revolution while the other shaft remains stationary and note the T.I.R.

Unless otherwise specified by the coupling manufacturer, offset misalignment should be limited to 0.005 inches T.I.R.

Adjust the alignment by loosening the pump or driver mounting bolts and retighten or shim as required.


Figure 1


Measuring Offset Misalignment With A Dial Gauge

Figure 2
Measuring Angular Misalignment With A Dial Gauge


In areas where a dial indicator arrangement is not available, an adequate job of alignment can be done with a straightedge. This method is especiallyuseful if the coupling used contains a rubber drive element.

To check offset misalignment, lay the straightedge in line with the shafts on the O.D.’s of the coupling halves. There should be no gaps under the straightedge. Check two locations 90 degrees apart. Angular misalignment can be checked by measuring the gap between coupling half faces. There should be no more than a 1/64 inch gap under the straightedge or a 1/64 inch variation in the gap between the coupling halves. See Figures 1A and 2A.


Figure 1A
Measuring Offset Misalignment Using a Straightedge


Figure 2A


Measuring Angular Misalignment Using A Straightedge


Note: Further reference on coupling alignment can be found in Hydraulic Institute Standards, 13th edition, pages 177, 120.
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Types of Gears


A SPUR GEAR
is cylindrical in shape, with teeth on the outer
circumference that are straight and parallel to the axis (hole).
There are a number of variations of the basic spur gear,
including pinion wire, stem pinions, rack and internal gears.
(See Figure 1.17)


PINION WIRE
is a long wire or rod that has been drawn
through a die so that gear teeth are cut into its surface.
It can be made into small gears with different face widths,
hubs, and bores. Pinion wire is stocked in 4 ft. lengths.
(See Figure 1.18)


STEM PINIONS
are bore-less spur gears with small numbers of
teeth cut on the end of a ground piece of shaft. They are
especially suited as pinions when large reductions are
desired. (See Figure 1.19)


RACK
are yet another type of spur gear. Unlike the basic spur
gear, racks have their teeth cut into the surface of a straight
bar instead of on the surface of a cylindrical blank. Rack is
sold in two, four and six foot lengths, depending on pitch,
which you will learn about starting in chapter 2.
(See Figure 1.20)


INTERNAL GEARS
have their teeth cut parallel to their shafts
like spur gears, but they are cut on the inside of the gear blank.
(See Figure 1.21)


HELICAL GEARS
A helical gear is similar to a spur gear except that the teeth
of a helical gear are cut at an angle (known as the helix
angle) to the axis (or hole). Helical gears are made in both
right and left hand configurations. Opposite hand helical
gears run on parallel shafts. Gears of the same hand operate
with shafts at 90-degrees. (See Figure 1.22, 1.23, 1.24, 1.25)


BEVEL GEARS
A bevel gear is shaped like a section of a cone and usually operates
on shafts at 90-degrees. The teeth of a bevel gear may be straight
or spiral. If they are spiral, the pinion and gear must be of opposite
hand in order for them to run together. Bevel gears, in contrast
to miter gears (see below), provide a ratio (reduce speed) so the
pinion always has fewer teeth. (See Figure 1.26, 1.27)

MITER GEARS
Miter gears are identical to bevel gears except that in a miter
gear set, both gears always have the same number of teeth.
Their ratio, therefore, is always 1 to 1. As a result, miter gears
are not used when an application calls for a change of speed.
(See Figure 1.28, 1.29)

WORMS & WORM GEARS
WORM Worms are a type of gear with one or more cylindrical
threads or “starts” (that resemble screw threads) and a face that
is usually wider than its diameter. A worm gear has a center
hole (bore) for mounting the worm on a shaft. (See Figure 1.30A)

WORM GEARS – like worms – also are usually cylindrical and
have a center hole for mounting on a shaft. The diameter of
a worm gear, however, is usually much greater than the
width of its face. Worm gears differ from spur gears in that
their teeth are somewhat different in shape, and they are
always formed on an angle to the axis to enable them to
mate with worms. (See Figure 1.30B)

Worms and worm gears work in sets, rotating on shafts at right
angles to each other, in order to transmit motion and power
at various speeds and speed ratios. In worm and worm gear sets,
both the worm and worm gear are of the same hand. (Because
right- hand gearing is considered standard, right-hand sets will
always be furnished unless otherwise specified.) (See Figure 1.30)

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