Heavy Duty Balanced Opposed Compressors

FOR MODELS: JG AND JGA SECTION 5 - MAINTENANCE
Piston and Rod - Removal
!
CAUTION
TO PREVENT PERSONAL INJURY, ENSURE THAT COMPRESSOR
CRANKSHAFT CANNOT BE TURNED BY THE DRIVER OR COMPRES-
SOR CYLINDER GAS PRESSURE DURING MAINTENANCE: -- ON
ENGINE-DRIVEN COMPRESSORS, REMOVE THE CENTER COUPLING
OR LOCK THE FLYWHEEL. -- ON ELECTRIC MOTOR-DRIVEN COM-
PRESSORS, IF IT IS INCONVIENIENT TO DETACH THE DRIVER FROM
THE COMPRESSOR, THE DRIVER SWITCH GEAR MUST BE LOCKED
OUT DURING MAINTENANCE.
BEFORE PERFORMING ANY MAINTENANCE, COMPLETELY VENT
SYSTEM. BEFORE REMOVING A CYLINDER HEAD, BACK OFF ALL
CAPSCREWS 1/8" (3 mm). MAKE SURE THE HEAD IS LOOSE AND THE
CYLINDER IS COMPLETELY VENTED.
1. Remove the crosshead guide side covers and the cylinder head. The cylinder
head is to be loosened first to the Caution! instructions above.
2. Move the crosshead to its inner dead center position. Back off, but do not
remove, the crosshead nut set screws. Loosen the crosshead nut with the special
slugging wrench, (see Figure 7-1: on page 7-3) and a slugging hammer. Use
the open-end wrench for hex nuts and the peg wrench for round nuts.
3. Remove the cylinder head. In the case of tandem cylinders where the outboard
cylinder bore is smaller than the inboard bore, it is necessary to remove the outboard
cylinder. Support such cylinders during removal and installation, as to not
put excessive weight on the piston and rod assembly which might cause bending.
4. Use the Piston Nut Spanner and speed wrench to screw the piston and rod
assembly out of the crosshead. The two dowels on the Piston Nut Spanner fit
the holes in the piston nut. Turn the crosshead nut off the piston rod.
5. As the piston leaves the cylinder, be careful in handling the piston rings. Despite
their toughness in service, rings are fragile with regard to removal. Always handle
them with clean tools and hands protecting the rings from nicks, marring,
and bending. Move the piston out of the cylinder until a fraction of the first ring
clears the cylinder. Encircle the ring by hand (use a band for larger sizes) until it
is clear and remove it. Use this same procedure to remove the succeeding rings
and wear band.
6. Slide the piston rod assembly out of the head end. The threaded crosshead end
of the rod is 1/8 inches (3 mm) smaller in diameter than the inside diameter of
the packing. Using extreme care, slowly slide the piston rod through the packing
to avoid damaging the rod threads or the packing rings.
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