CHAPTER 3 BOW CRANE SYSTEM
Section I. Description and data
Description. The bow crane is a hydraulically operated articulating boom crane with a maximum outreach of
approximately 47 feet. Maximum lift capacity at this extension is 2,425 pounds. Maximum lift is 41 ,895 pounds at an
outreach of only 6 feet, 7 inches.
The crane is corrosion-proof and suitable for operation in a marine environment. The crane has five major
assemblies: crane body, inner boom, outer boom, mounting base, and hydraulic control unit. When not in daily use, bow
crane must be placed in its traveling (stowed) configuration (Figure 3-1). The crane body is a steel casting with the upper
part being a closed welded box design through which hydraulic hoses are routed to inner and outer boom actuating
cylinders. Inner and outer boom assemblies are positioned, as required, by extending or retracting hydraulic actuators. A
winch assembly is mounted on top of the primary element of the boom for retrieving loads of 10,000 pounds or less. To
winch loads greater than 10,000 pounds, the sheave block must be installed on the end of the outer boom.
Operator controls for the crane (Figure 3-2 for Barge 1 and Figure 3-3 for Barges 2 and 3) are on the forward side
of the deckhouse top. They include five control levers for controlling crane movement, a START/STOP control switch, and
a key lock for the anti-2-block control system. The START/STOP control switch and anti-2-block key lock are in a
watertight storage box aft of the crane control levers. Another START/STOP control switch, primarily for emergency use,
is on the weather deck forward bulkhead.
Hydraulic pressure for the bow crane is supplied by a hydraulic power unit in void 1 port. A 30 Hp electric motor
drives the pump to produce 3600 psi of hydraulic pressure. A motor controller in void 1 (Figure 3-4), starts and stops the
local unit and supplies power to the two remote START/STOP control switches. The motor controller requires 440 Vac, 3
phase, 60 Hz power. Bow crane system installation is shown on drawings listed in Appendix A.
Capabilities. The bow crane is primarily used for launching and retrieving the barges work boat and for loading
and unloading the shore winch. It is also used to move barge batteries, located on top of the deckhouse, and other
equipment and supplies.
The cranes control valve system has built-in pressure relief valves that protect the various hydraulic
components in the event the crane is overloaded. In case of overload, the boom will begin to drop at a
slow rate. Correct this condition before continuing the lifting operation.
A Non-Commissioned-Officer-in-Charge (NCOIC) must be present to direct operator in crane movement
of material. Position the NCOIC so that he can direct crane operation with a standard system of hand
signals (Figure 3-5). To avoid any confusion during lifting operation, only the NCOIC gives these signals.
The crane operator and NCOIC should check with each other before using hand signals, to be sure that
each person clearly understands all signals. As an alternate method, the NCOIC and crane operator can