Heavy Duty Balanced Opposed Compressors

FOR MODELS: JG AND JGA SECTION 5 - MAINTENANCE
!
CAUTION
CROSSHEADS ARE HEAVY. CARE MUST BE TAKEN WHEN
HANDLING TO AVOID PERSONAL INJURY. THE WEIGHT OF
EACH CROSSHEAD IS LISTED IN THE BALANCE SHEET
THAT COMES IN THE MANUAL WITH EACH COMPRESSOR.
1. Remove crosshead guide side covers and cylinder head.
2. Move the crosshead to its inner dead center position and back off, but do not
remove, the crosshead nut set screws. Loosen the crosshead nut with the special
slugging Peg or Open End Wrench shown in Figure 7-1: on page 7-3,
depending on nut style, and a babbitt or plastic-faced slugging hammer.
3. Use the Piston Nut Spanner (Torquing Adaptor) shown in Figure 7-1: and a
speed wrench to screw the piston rod out of the crosshead. The two dowels on
the Adapter fit holes in the piston nut. Turn the crosshead nut off the piston rod.
Push the rod end forward to the edge of the packing to provide a clearance for
crosshead removal.
4. With the crosshead in its outer dead center position, remove the crosshead pin
thru bolt, lock nut, end-plates and pin.
5. Turn the crankshaft to its inner dead center position. Move the crosshead to its
outer dead center position to be free of the connecting rod. Make sure the connecting
rod does not drop and damage the crosshead guide surface.
6. Roll the crosshead 90 degrees and remove it through the guide opening.
7. Check the crosshead pin to bushing clearance. (See Table 1-2 on page 1-8.)
Wear on the pin can be determined by a visual inspection. Replace the pin if
necessary. If the bushings need to be replaced, hacksaw or file to within 1/32
inches (1 mm) of their thickness. They can be easily drifted out. A press will be
needed to install new bushings. The bushing can be installed in the crosshead
by cooling the bushing in a dry ice and alcohol solution. The bushing needs to
be left in the solution long enough to reach the same temperature as the solution,
about -120° F (-85°C). DO NOT TOUCH COLD SURFACES WITHOUT
PROPER INSULATION TO PREVENT INJURY. Bronze crossheads do not
have bushings; if the crosshead pin bearing area is worn, these crossheads
should be replaced.
NOTE: THE SIDE OF THE CROSSHEAD RECEIVING THE NEW BUSHING SHOULD BE
SUPPORTED DIRECTLY TO PREVENT POSSIBLE CRUSHING OF THE
CROSSHEAD BY THE PRESS. (SEE FIGURE 5-3:)
ABSOLUTE CLEANLINESS IS REQUIRED OF BOTH BUSHING AND CROSS-
HEAD TO PREVENT DIRT FROM ACCUMULATING BETWEEN THE BUSHING
AND CROSSHEAD BORE.
8. Visually inspect the shoe surfaces for scoring. Since they are constantly lubricated
under pressure during operation, there should be virtually no wear.
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