3-7
3.7 COMPRESSOR RUNNING GEAR
REASSEMBLY
a. Seal End Main Bearings
1.
When installing new seal end main bearings the
oil groove is on top of the compressor with V grooves
pointing to each other. When installed, there must be a
5/16 inch (7.93 mm) gap between the two bearings (See
Figure 3-14).
2. Line boring seal end main bearings.
TOP OF COMPRESSOR
5/16
GAP
Figure 3-14. Seal End Main Bearings
b. Pistons, Rods, and Rings
Prior to installing new piston rings, it is necessary to
break the hard glazed surface of the cylinder in order to
reduce the wearing-in period of the new rings. Break the
glaze by honing lightly in an up and down rotating motion.
Clean thoroughly after breaking glaze.
Some 05G compressors for refrigeration use only
may have contoured pistons (See Figure 3-15). When
installing contoured pistons into compressor, check
suction valve and contoured piston are in the same
orientation.
Figure 3-15. Contoured Piston
1.
The gap between the ends of the piston rings can
be checked with a feeler gauge by inserting the ring into
the piston bore about one inch below the top of the bore.
Align the ring in the bore by pushing it slightly with a
piston. The maximum and minimum allowable ring gaps
are shown in Table 3-2.
2.
Install the piston and rod assemblies up through
the bottom of the crankcase and into the cylinders. Allow
pistons to extend beyond the top of the cylinder to enable
installation of piston rings. Pistons must be installed so
that the chamfer, on the connecting rod, faces toward the
crankshaft journals. Center rods on each crankshaft
throw may be installed in either direction. (See
Figure 3-16)
CHAMFERED EDGE
CHAMFERED EDGE
SEAL END
THRUST
WASHER
Figure 3-16. Installing Piston Rod Assemblies and Seal
End Thrust Washer
3.
Depending on date of manufacture, the
compressor may be fitted with double or single ring
pistons. Double ring and single ring pistons may be
installed in the compressor, as long as matched pistons
are used on each bank.
4.
Old double ring pistons (with wider lower ring
groove), the oil ring is installed in the groove nearest the
bottom and the compression ring in the groove nearest
the top. The oil ring is notched on the outside
circumference. This notch must be installed towards the
bottom. (See Figure 3-17)
Compression Ring
Oil Ring
OLD
Compression Ring
Compression Ring
NEW
Figure 3-17. Piston Rings
5.
The compression ring is chamfered on the inside
circumference. This ring is installed with the chamfer
towards the top. If using a double ring piston, stagger the
ring end gaps so they are not aligned.
6.
Measure side clearance between ring and ring
groove in piston. Maximum dimensions are provided in
Table 3-2.
