SUB-SECTION 4C
ROTARY JOINTS
9. Remove the capscrews and lockwashers securing the
hydraulic swivel to the revolving frame deck. Then carefully
lift the hydraulic swivel straight up until it clears the stem
of the collector, and remove the hydraulic swivel to a suit-
able repair area.
OVERHAUL. Overhaul of the rotary joint consists only of
seal replacement. To replace the rotary joint seals, proceed
as follows (see Figure 4C-2):
1. Remove the snap ring at the top of the hydraulic rotary
joint.
2. Carefully remove the outer body from the inner stem.
3. The outer body bore should be thoroughly washed with
a suitable cleaning solvent or diesel fuel, and inspected for
signs of scoring or deep scratches. If excessive scoring or
deep scratches are found, the entire rotary joint should be
replaced.
NOTE
Excessive scoring or deep scratches are usually caused
by foreign material in the hydraulic system. If these
defects are found the hydraulic system should be
checked for foreign material.
4. The inner stem should be thoroughly washed with a
suitable solvent or diesel fuel. The teflon seals should then
be inspected for deep scratches or severe damage.
NOTE
The teflon seals and the loading O-rings under the
Figure 4C-2. Rotary Joint (979J30)
seals should not be removed unless the seals show
signs of deep scratches or severe damage, since re-
1. Disconnect the ground cable from the battery.
movel of these seals will damage them beyond use.
2. Tag and disconnect the electrical wires in the junction
In the event a seal must be replaced, use the following
box at the top of the hydraulic swivel.
procedure:
3. Remove the upper snap ring on the air swivel, and
A. Generously lubricate the spool with clean hydraulic
remove the outer body of the swivel. Remove the lower
oil.
snap ring and thrust washer.
B. Carefully install a new loading O-ring in the seaI
4. Loosen the setscrews in the collar at the bottom of the
groove.
junction box, and remove the junction box.
C. Walk a new seal into place in the same manner the
bead of a tire is walked onto a wheel rim.
5. Tag and remove the hydraulic lines attached to the outer
body of the swivel.
D. Knead the seal by hand to squeeze it into the seal
6. Tag and remove the hoses attached to the O-ring elbow
groove.
fittings in the lower portion of the inner stem.
5. Generously lubricate the outer body bore and inner
stem with clean hydraulic oil.
7. Working either up from below the carrier or down
through the opening in the revolving frame, remove the
6. Place the outer body in a vertical position with the bot-
O-ring elbow fitting, from the lower portion of the inner
tom of the body up. Insert the top of the inner stem into
stem.
the body bore, and while the stem is being lowered into the
body compress the teflon seals by hand as they enter the
8. Remove the two capscrews which connect the collector
bore.
assembly to the bottom of the hydraulic swivel.
4C-3
