Installation of products is part of the precast producer's marketing approach. Equipment selection should be based on product attributes and required reach.
Truck-mounted unloading equipment options for producers include A-frame boom rigs, telescoping cranes and articulating (also called knuckle-boom) cranes. Selection of unloading equipment depends upon existing or anticipated product weights and typical required reach.
Designs differ, but A-frames typically handle up to 7 tons. Most have 10- to 25-foot reach from the rear of the truck; however, lifting capacity declines as reach increases. Short outriggers on the back prevent the truck from tipping over when the boom is moved laterally. An A-frame may cost less than half as much as a truck-mounted crane.
Truck-mounted telescoping and knuckle-boom cranes have pedestals that allow 360-degree boom rotation. Operators can unload products from the side of the truck and install them a greater distance from the truck bed. Lifting capacity increases as the boom angle approaches 90 degrees in relation to the truck bed.
Some telescoping types have a cable, attached to a winch, that runs the length of the boom. A hook-and-pulley located at the end of the cable moves vertically. One model handles 13,300 pounds and 12,000 pounds at 20 and 24 feet from the truck, respectively. A higher-capacity model handles 20,000 pounds at 20 feet and 16,000 pounds at 25 feet from the truck. Precast products can be lowered to 10 feet below grade with this equipment, which costs up to $250,000.
Knuckle-boom cranes, which also cost up to $250,000, require no overhead storage area during transport. Delivery of taller products is possible, since the boom is not extended between crane and cab during transport. Producers can lift up to 9 tons at a 20-foot reach (30-degree boom angle) and 8 tons at a 25-foot reach with the boom parallel to the truck bed. Because they can reach to a greater depth below grade, these cranes are especially useful for installing manholes.
In recent years, smoother-operating controls for both telescoping and knuckle-boom cranes have become more responsive. Older solenoid designs open and close hydraulic valves completely, resulting in a short, "jerky" movements. Newer controls have fully proportional valves and hydraulic fluid flow. This results in safer operation and reduced product damage.
OSHA requires producers to provide a designated inspector of equipment before and during use and a documented daily and annual inspection. The biggest operating hazard is overhead power lines. Operators must assume lines are live, and a clearance of no less than 17 feet is recommended. Drivers should move beyond the boom's reach in relation to power lines before extending or unfolding.
KEYWORDS: crane, delivery, unload