Ariel JGJ Series, Technical Manual

Page: 93 / 141

F
OR
M
ODELS
: JGW, JGR
AND
JGJ S
ECTION
5 - M
AINTENANCE
1/01 PAGE 5 - 21
4. Check piston rings and wear band (when used) to determine wear (see “Deter-
mining Ring Wear:” on page 5-24 and “Determining Wear Band Wear:” on page
5-24). Replace piston rings and wear bands as required.
5. Assemble the piston, rod, collar and nut by hand.
6. Secure the piston rod in Torque Fixture D-0961. Tighten the piston nut to the
recommended torque in Table 1-11 on page 1-15. It may be necessary to use a
torque multiplier to achieve the required torque.
7. Install the set screws and prick-punch the piston nut to lock them in place.
8. The set screws should be so tight that the Allen Wrench is slightly deformed
(twisted) after tightening.
NOTE: ONE END OF SINGLE PIECE PISTONS ARE MACHINED 0.002" (0.050 mm)
UNDERSIZE ACROSS A 3/4 INCH (20 mm) WIDE BAND FOR MANUFACTUR-
ING PURPOSES. THIS IS THE HEAD END OF THE PISTON.
Piston and Rod - Installation
1. Install the piston/rod assembly with piston rings and wear band into the cylinder.
The threaded crosshead end of the rod is 1/8 inches (3 mm) smaller than the
inside diameter of the packing. It is not necessary to use an entering sleeve if
reasonable care is taken, but a sleeve may be helpful. Using a non-metallic
sleeve from the crosshead side will help ensure that packing rings are not dam-
aged.
2. Screw the crosshead nut onto the piston rod. Make sure all threads and nut
seating surfaces are well lubricated with clean, fresh oil to ensure proper assem-
bly. Position the crankshaft in the inner dead center position. Remove a crank
end discharge valve. Determine the required piston crank end clearance as
shown on the cylinder identification plate. Refer to Table 1-3 on page 1-9. Insert
a feeler gage, equal to the required crank end clearance, thru the discharge
valve pocket. Use the tools illustrated in Figure 5-11: on Page 5-19 to screw the
piston rod into the crosshead until piston is snug against the feeler gage. Snug
the crosshead nut, but do not tighten. Remove the feeler gage.
3. Ensure that the Piston Turning Tool has been removed. Replace the cylinder
head and gasket. Tighten all cylinder head bolts evenly to the proper torque
value listed in Table 1-11 on page 1-15.
4. Remove a head end suction valve. Determine the required piston head end
clearance as shown on the cylinder identification plate. Refer to Table 1-3 on
page 1-9. Rotate the crankshaft 180° to the outer dead center position, and
using the feeler gages thru the valve pocket, check the head end clearance.
Determine that measured clearance is within the required clearance limits.
5. Tighten the crosshead nut to the proper torque value listed in Table 1-11 on
page 1-15.
6. Tighten set screws in the crosshead nut.
7. Before installing the side covers, apply an anti-seize lubricant to the gaskets.
This will aid removal at a later date.
8. Replace the crosshead guide side covers; tighten all capscrews.
9. Replace the valve assemblies, tighten all valve cap bolts evenly to the proper
torque value listed in Table 1-11 on page 1-15.