Truck-Mounted Cranes

The truck-mounted crane (fig. 12-6) consists of a truck carrier and house (upper revolving unit) and is categorized under the 82-00000 USN number registration series. The truck carrier can travel from different jobsites at 20 to 35 mph.

Figure 12-6.-Truck-mounted crane.

Truck cranes have a high ground bearing pressure, ranging from 75 to 100 psi due to the pneumatic tires on which the machine travels. On a firm, dry surface, a truck carrier can climb a 40-percent grade. Depending on the design of the carrier, the turning radius can range from 50 to over 90 feet. This high turning radius limits its maneuverability.

Before any crane travels to a jobsite, the crane crew supervisor must visually review the planned travel route to determine if low wires, low overpasses, narrow bridges, or other unsafe obstacles exist. The absolute limit of approach for power lines (fig. 12-7) is the following:

1. 0 to 125,000 volts, 10 feet

2. 125,000 to 250,000 volts, 15 feet

3. Over 250,000 volts, 25 feet

Anytime you are traveling with a crane, stay a minimum of 4 feet from any electrical power source.

When traveling with a truck-mounted crane equipped with a lattice boom, do NOT rest the boom on the cradle, as the lower cords of the boom can be dented if the boom bounces while traveling. Position the boom 2 to 4 inches above the cradle.

Truck- and wheel-mounted cranes are rated at 85 percent of the minimum weight that can cause the crane to tip at a specified radius with the basic boom. The truck carrier is equipped with outriggers that provide more stability for the crane; therefore, when you are making crane lifts, the outriggers should always be used.

As outlined in the COMSECOND/COM-THIRDNCBINST 11200.1, Naval Mobile Construction

Figure 12-7.-Limit of approach for power lines.

Figure 12-8.-Truck-mounted crane quadrants of operation.

Battalion, Equipment Management, rated free loads or pick and carry operations will only be performed according to NAVFAC P-307 during a crane certification, in case of an emergency, or as directed by the crane certifying officer.

Depending on the make and model, most truck-mounted cranes have a 270-degree working area. Some truck-mounted cranes are equipped with an optional front outrigger that provides a 360- degree working area The quadrants of operation for truck-mounted crones are over the side, over the rear, and over the front if equipped with the front outrigger (fig. 12-8).

Figure 12-9.-Wheel-mounted cranes.

NOTE: The capacity of the crane may change when rotating a load from one quadrant to another. This information is provided on the crane load chart.