Outrigger setup: meaning and why it matters

The parts

• Beams. The horizontal members that slide out from the carrier. A chart usually names the beam position it was rated for, such as fully extended, or an intermediate position where the crane has one.
• Jacks. The vertical cylinders at the end of each beam. They take the crane's weight onto the floats and level the carrier.
• Floats. The pads at the foot of each jack.
• Mats or cribbing. Material under the floats that spreads the load into the ground. See outrigger mats and ground pressure.

Why the chart cares

The wider the outriggers, the farther the tipping axis sits from the crane's center, and the more the crane can lift at a given radius. So the manufacturer prints ratings per beam position. On our invented chart PC-1, a 60 ft boom at a 20 ft radius is rated 31,000 lb gross with fully extended outriggers. The mid-extension table for the same boom and radius reads 23,000 lb. At 25 ft the pair is 24,500 lb and 18,000 lb. Same crane, same boom, same radius, but a different setup and a different capacity.

If the beams are not out as far as the chart's table assumes, that table does not apply. Read the table for the setup you actually have, and check the chart's notes for whether beams may be set to different extensions on different sides.

A setup check, in order

1. Which setup does the chart table name?
2. Are all beams at the extension that table needs?
3. Are the jacks extended and the crane level to the manufacturer's limit?
4. What is under each float, and is it large and firm enough? OSHA 29 CFR 1926.1402 covers ground conditions for crane work.

Common mix-ups

• Reading the fully extended table on partly extended beams. It is the most expensive mistake on the written exam, because the capacity it gives is too high.
• Mixing the setup with the working area. They are separate settings that the chart pairs. See quadrant of operation.
• Assuming the floats can sit on bare ground. The chart does not rate the ground, so you check it.
• Skipping the level check. Rated capacities assume the crane is level within the manufacturer's limit.

On the NCCCO written exam

Setup shows up in three places under the 01/25 outline. Site tasks 1.1 and 1.2 cover ground stability, mats and cribbing (Site is about 22% of Core). Operations tasks 2.1 to 2.4 cover leveling. Load Charts, about 27%, is where you choose the table. A problem that says the beams are partly extended is testing whether you reach for the right table.

Practice it

The outrigger pad calculator sizes mats from a float load and a ground bearing value. Then read outrigger mats and ground pressure and quadrant of operation. The crane terms glossary has the rest of the set.

Know the terms? Take the free 10-question check

Take the free 10-question check. It is scored by the Core outline domains and needs no signup, so you see whether site, operations, technical knowledge or load charts costs you the most points. Boom Angle's course then gives you a question bank with each answer key checked by a second solve, timed practice exams, and a study plan built from your exam date.

Sources

Show the list

• 29 CFR 1926.1402: Ground conditions, OSHA.
• 29 CFR 1926.1404: Assembly/Disassembly, general requirements, OSHA.
• Mobile Crane Operator Candidate Handbook, CCO, Core outline tasks and weights (01/25 revision). Task numbers on this page follow it.