3.3 Mobile and Support Equipment: Forklifts, Aerial Lifts, and Mobile Cranes

Powered industrial trucks

Module 32112, Mobile and Support Equipment is the third module in the Rigging and Mobile Equipment domain. Its center of gravity — appropriately — is the forklift.

The stability triangle

A counterbalanced forklift is supported at three points: the two front wheels and the pivot point of the steer axle. Connecting those three points forms the stability triangle. The truck stays upright as long as the combined center of gravity of the truck and its load stays inside that triangle. Every forklift rule descends from that single fact:

• Raising a load raises the combined center of gravity and makes the triangle easier to escape.
• Turning shifts the center of gravity laterally toward a side of the triangle; turning with a raised load is the classic tipover.
• Braking hard shifts it forward toward the front axle line.

Capacity and the load center

The data plate states rated capacity at a specified load center, most commonly 24 inches measured from the face of the forks to the center of gravity of the load. The rating is not a single number; it is a number tied to that distance. A load whose center of gravity sits farther out — a long bundle of pipe, a motor on a pallet pushed to the outer edge — exerts more moment and the safe capacity drops. Attachments such as drum clamps and side shifters also reduce net capacity, and the data plate must reflect them.

Operating rules that appear as items

Operators must be trained, evaluated, and authorized under 1910.178(l), and their performance must be evaluated at least once every three years. Refresher training is required after an accident, a near miss, an observed unsafe operation, a change of truck type, or a change in workplace conditions. A pre-use inspection — forks, chains, tires, horn, lights, brakes, hydraulics, leaks, data plate — is required at the start of each shift.

Aerial lifts

Maintenance mechanics reach overhead conveyors, fan drives, and pipe racks from aerial lifts.

• Boom-supported lifts (articulating and telescoping booms): a body harness with a lanyard attached to the boom or basket is required. Attaching to an adjacent structure is prohibited, because the basket can move away and leave the worker suspended or pull them out.
• Scissor lifts: the guardrail system is the primary fall protection. Chains or gates across the entry must be closed. Do not stand on the midrail or toeboard to gain height.
• Universal rules: never exceed the rated platform load; do not move an elevated boom lift unless the manufacturer permits it; keep both feet on the platform floor; do not use planks or ladders in the basket; inspect before each shift; and check for overhead obstructions and energized lines before elevating.

Mobile cranes

Mechanics rarely operate the crane, but they rig to it and act as signal persons, so the assessment expects the fundamentals.

1. The load chart governs. A crane's capacity depends on boom length, boom angle, load radius, quadrant of operation, counterweight, and whether it is on outriggers or on rubber. The single largest number on the chart applies only at the shortest radius. Capacity decreases as the load radius increases.
2. Outriggers must be fully extended and set per the chart configuration being used, with pads or cribbing sized for the ground bearing pressure. Partially extended outriggers require the chart for that configuration, if one exists.
3. Ground conditions matter more than most crews assume. Soft fill, buried trenches, and utility vaults have dropped more cranes than overload.
4. Power line clearance. No part of the crane, load line, or load may come closer than 10 feet to an energized overhead line rated up to 50 kV; greater clearance is required above that voltage. A dedicated spotter is used when the crane operates near the minimum distance.
5. Two-blocking — the hook block contacting the boom tip — can part the hoist rope. Anti-two-block devices exist for this reason, and signal persons must watch headroom during hoisting.
6. Side loading the boom is prohibited. Cranes lift vertically; dragging a load sideways to break it free can buckle a lattice or telescoping boom.

Before any critical lift the crew confirms: load weight, rigging weight, radius, boom configuration, chart capacity, the percentage of capacity being used, ground conditions, clearances, and who is giving signals.