F
OR
M
ODELS
: JGI, JGM, JGN, JGP
AND
JGQ
S
ECTION
5 - M
AINTENANCE
PAGE 5-33
Determining Wear Band Wear:
Since the wear band does not work as a sealing ring, end gap is not critical. The amount of
wear band projection beyond the outer diameter of the piston is important. Wear band pro-
jection can be checked by measuring piston to cylinder bore clearance at the bottom of the
bore. This can be done without removing the piston from the cylinder. Replace the wear
band before it has worn enough to allow the piston to touch the cylinder bore.
Wear Band - Installation
Install the wear band as if it was another piston ring as above. Wear bands are only used on
1-3/4JG-FS-HE and 1-3/4SG-FS-HE cylinder class pistons.
Piston Rod Pressure Packing - Removal
CAUTION!: BE SURE THAT ALL PRESSURE IS RELIEVED FROM THE COMPRESSOR
CYLINDERS PRIOR TO REMOVING PACKING.
1.
Remove the piston and piston rod. See “Piston and Rod - Removal” on page
5-27.
2.
Remove packing diaphragm and oil wiper packing.
3.
Disconnect all tubing connections from the top of the packing flange and the pri-
mary vent tube from the bottom of the flange. Remove the twelve point cap
screws that hold the pressure packing flange to the cylinder.
4.
At this point do not remove the small nuts from the studs. These studs hold the
entire packing case together so it can be removed as an assembly.
5.
Screw two short 3/8-16 UNC cap screws into the two tapped holes provided in
the crankend face of the packing flange. An appropriate prybar under the heads
of the cap screws can be used to pull the entire pressure packing out into the
crosshead guide. It will then come out through the side opening of the guide.
The pressure packing may now be taken to a clean place for disassembly.
6.
Set the pressure packing on a clean surface on its nose cup or cylinder end.
Three long tie studs hold the pressure packing together. The stud holes are not
equally spaced. This prevents the stack of parts from being aligned incorrectly.
Remove the stud nuts and the pressure packing can be unstacked. Replace
these nuts each time the pressure packing is serviced.
7.
Ring wear can be determined by placing the assembled rings, (note
match-marks), on the piston rod. Check end gap clearance. If the ends butt, or
nearly butt, they should be replaced by new rings. See “Types of Piston Rod
Packing Rings” on page 5-35.
8.
Fins or wire edges on the rings due to wear should be carefully filed off so that
all matching edges will be square.
9.
The metal gasket on the end cup can be pried loose with a sharp awl. Be careful
not to scratch the sides of the gasket groove.
10. Before reassembly be certain all parts are perfectly clean.