TM 9-4940-568-10
2-121
2-29. MATERIAL HANDLING CRANE (MHC) OPERATION.
a.
General Description.
During operation, the material handling crane (MHC) has four basic functions: boom telescoping, boom elevation,
swing and hoist. The boom can rotate 300 degrees. The crane has a lifting capacity up to 10,000 lbs (4,536 kgs) at 14
ft. (4.3 M) radius (see lifting capacity chart located at control panel for further information).
The crane is operated by hydraulics supplied by a hydraulic pump mounted on the diesel engine through the crane’s
main control panel. The main control panel provides the controls to operate all functions of the crane. The outrigger
control panel provides the controls to operate the outrigger functions.
Each control on the crane’s main control panel is proportional. The more travel of the control, the faster the selected
crane movement. The crane may also be operated by a remote control unit with the same operating functions, except
for outrigger controls and mast control, as the main control. Left and right retractable outrigger jack cylinders are
provided to stabilize, support, and level the system while the crane is operated. Built within the crane’s hydraulic
system are several safety features that protect the equipment and operating personnel. They are as follows:
Hold valves will prevent a load from falling in the event of pressure loss because of hydraulic line
failure.
A suspended load on the crane can be lowered if hydraulic pressure is lost at the hydraulic pump on
the diesel engine if external hydraulic lines from the PLS truck are attached to the quick disconnect
couplings at the back of the crane. Should hydraulic failure occur in the crane, the suspended load
can be lowered by using the emergency hand pump. This procedure should be done by Unit
Maintenance personnel.
An overload protection system that prevents lifting greater loads, at a given distance, than the crane
can handle. All functions that decrease overload remain functional: hoist down, telescope in, and
swing left or right.
