BOOM RT880E SERVICE MANUAL
4-2 Published 11-10-2014, Control # 524-00
boom section and the barrel is secured to the outer mid
boom section by a trunnion. The extension cables are
secured to the back of the fly section and run around
extension sheaves on the cylinder mounted fly sheave
mount to the cable anchor at the lower cylinder.
The hydraulic fluid in both lower and upper telescope
cylinders is routed through the rods so that the barrels can
extend. There are two cam operated check valves which
control flow to the telescope cylinders. With both cylinders
retracted, the check valve for the lower telescope cylinder is
open and the check valve for the upper cylinder is closed
allowing the lower cylinder to extend. When the lower
cylinder is fully extended, the check valve for the upper
cylinder opens allowing the upper cylinder to extend. The
check valve for the lower cylinder closes after the upper
cylinder starts to extend and shuts off the flow to the lower
cylinder. As the upper telescope cylinder barrel extends, the
extend cables around the extend sheaves push on the
extend cables to pull the fly section out at the same time the
outer mid is extending.
Boom Retraction
The upper telescope cylinder retracts the outer-mid and two
retract cables pull the fly section in at the same time. When
the upper cylinder is fully retracted, the check valve for the
lower telescope cylinder is opened and the lower cylinder
starts to retract. The check valve for the upper cylinder is
closed as the lower cylinder starts to retract. The outer mid
and fly retract first and then the inner mid.
MAINTENANCE
Removal
NOTE: The boom weighs approximately 22,090 lb (10,020
kg). Removal of the swingaway boom extension
will simplify boom removal, therefore, the above
weight is for the boom without the swingaway
boom extension attached.
1. Extend and set the outriggers to level the crane and
ensure the boom is fully retracted and in a horizontal
position over the front of the crane.
2. If equipped, remove the swingaway boom extension and
auxiliary nose according to the removal procedures in
this section.
3. Remove the hook block or headache ball and wind all
the wire rope onto the hoist drum.
4. Position the boom to make sure that the lift cylinder is
resting securely in the lift cylinder support.
5. Attach a lifting device to the boom to provide for equal
weight distribution.
6. Tag and disconnect any electrical wiring from the boom.
7. Tag and disconnect the hydraulic lines to the lower tele-
scope cylinder.
8. Block the lift cylinder.
9. Remove the bolt, locknut and shim securing the upper
lift cylinder shaft to the side of the attach fitting on the
boom.
10. Remove upper lift cylinder shaft.
11. Take up the slack on the boom lifting device.
12. Remove clip pin and cross pin securing boom point pin
to base section.
13. Remove boom pivot pin.
14. Raise the boom clear of the crane and lower to ground
and set cribbing to support the boom and prevent tip-
ping.
Boom Disassembly
1. Remove the boom in accordance with the Removal pro-
cedures outlined in this section.
2. If necessary, on the left side of the boom remove the two
bolts and washers securing the RCL cable angle brack-
ets to the base, inner mid and outer mid.
NOTE: The boom weighs approximately 22,090 lb (10,020
kg) without the swingaway boom extension
attached.
CAUTION
Cuts and Abrasion Hazard!
Wear gloves when handling wire rope. Cuts and metal
slivers are possible if gloves are not worn.
DANGER
Ensure the lifting device is capable of supporting the
boom assembly.
DANGER
Crushing Hazard!
Ensure the boom lift cylinder is properly supported before
disconnecting it from the boom. Serious injury or death
may result from a falling lift cylinder.
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