The Definition of Outrigger Safety

Definition of Outrigger Safety

Outrigger safety is the set of practices for extending, positioning and supporting the outriggers or stabilizers on mobile cranes, boom trucks, knuckle boom cranes, aerial lifts and other equipment so the machine stays stable while lifting. Outriggers spread the machine's weight and load over a wider area, but they only work if they are set on ground that can carry the load, with adequate pads or cribbing, and deployed as the manufacturer's load chart requires. Poor outrigger setup is a leading cause of crane and lift tip-overs.

Key Facts About Outrigger Safety

• OSHA's crane standard (1926.1402) requires ground conditions to be firm, drained and graded so the equipment can be supported as the manufacturer specifies.
• Outrigger pad pressure can be very high, so pads or cribbing are used to spread force across a larger area of ground.
• Load charts are based on specific outrigger positions, such as fully extended, mid-extended or retracted.
• Hidden voids, such as underground utilities, septic tanks and recently backfilled trenches, can collapse under outriggers.

Example of Outrigger Safety

Before setting up a 60-ton mobile crane next to a building, the lift supervisor checks the site plan for buried utilities, confirms soil bearing capacity, places engineered crane mats under each outrigger, fully extends all outriggers as required by the load chart, and levels the crane before the lift.

How to Set Up Outriggers Safely

1. Assess ground conditions and identify underground hazards.
2. Use pads, mats or cribbing sized for the expected loads.
3. Extend outriggers as required by the load chart and manufacturer.
4. Level the machine and confirm all tires or tracks are clear as required.
5. Recheck outriggers during the work, especially after rain or freeze-thaw.

Related Terms

• Lift Plan
• Load Chart
• Knuckle Boom Crane
• Mobile Elevating Work Platform (MEWP)

Frequently Asked Questions: Outrigger Safety

Can I lift with outriggers partly extended?

Only if the manufacturer's load chart covers that outrigger position, and capacities are usually much lower than with outriggers fully extended.

Why do outriggers need pads or cribbing?

Pads spread the outrigger force over more ground, reducing ground pressure so the outrigger doesn't sink or punch through and tip the machine.

Who is responsible for ground conditions under a crane?

Under OSHA's crane standard, the controlling entity must make sure ground conditions are adequate and must tell the crane operator about known hazards beneath the setup area, such as voids or utilities.