Disassembly and Reassembly
60
Figure 98: Checking Axial Run Out
2. Fitting the drive coupling to the crankshaft of
the compressor is a critical operation when
installing a compressor. When the coupling is
removed, inspect the crankshaft taper and the
coupling for rust and pitting. A crankshaft or
coupling that has significant pitting on the
taper should be replaced. Crankshaft failures
in the taper area generally are the result of
improper fit between the coupling and the
crankshaft. Refer to “Drive Coupling” on
page 28 for the proper removal and
installation procedures.
Removal and Installing Crankshaft
Counterweights
Long stroke compressors have two add-on
counterweights riveted to the integral
counterweight portion of the cast crankshaft.
When regrinding crankpin journals, it is necessary
to remove the add-on counterweights which must
be plainly marked so they may be replaced exactly
as they were removed.
There have been some cases where a crankshaft
from a long stroke compressor was reground and
then installed without the add-on counterweights
being reinstalled. The result can be cracked
refrigerant lines, cracked frames and loose screws
due to an unbalanced condition.
To properly regrind a long stroke crankshaft, the
following procedure must be adhered to:
1. Mark the add-on counterweights, so they will
be reinstalled on the same integral
counterweight.
2. Drill off rivet head and drive out rivet with a
punch.
3. Regrind the crankshaft shaft to the new
undersized diameter. Bearing sets are
available in 0.005 in. (0.127 mm), 0.010 in.
(0.254 mm), 0.020 in. (0.508 mm) and 0.030
in. (0.762 mm) undersize. The standard
diameter of connecting rod journal is 1.3742
to 1.3747 in. (34.9047 to 34.9174 mm). The
clearance for the connecting rod bearing to the
crankshaft rod journal is 0.0008 to 0.0024 in.
(0.0203 to 0.0610 mm).
4. Tap holes in the integral counterweight with a
5/16-18 UNC tap.
5. Countersink the holes in the add-on
counterweight with an 82 degree tool to accept
5/16 flat head screws. This must be done
because the original countersink is 90 degrees.
6. Reinstall the add-on counterweights with
5/16-18 UNC flat head screws. Be sure to
install them on same integral counterweight
from which they were removed. Cut off the
excess screw length if required. Stake the
screws with a centerpunch to prevent screw
from backing out.
CAUTION: Misalignment of the flywheel
housing to the engine will cause
crankshaft fracture as indicated below:
1.
Misalignment Fractures Occur Here
2.
Coupling Problem Fractures Occur Here
Figure 99: Crankshaft Fractures
2
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AGA517
