Outriggers are one part of the support system
Stability depends on the load, radius, boom, support base, ground and vehicle together. Fully extended outriggers cannot make weak ground safe, and pads cannot resolve unknown voids or inadequate bearing conditions.
Start with the farthest required load position and the actual space available for deployment. Partial extension is usable only when the manufacturer provides an approved configuration. A small position change can move the lift into a different chart condition.
Review the support conditions assumed by the chart
Level, lift sector, weather limits and the transition from transport to working setup remain part of the assessment. The supplier needs representative site conditions to propose a compatible installation and support arrangement; the chart alone cannot establish those conditions.
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| Decision | What to establish | Condition or limit |
|---|---|---|
| Radius | Check the farthest required load position on the chart. | Small position changes can enter a different capacity range. |
| Outrigger geometry | Use only charted deployment configurations. | Partial or obstructed deployment may reduce or prohibit capacity. |
| Ground | Verify support reactions and suitable bearing surface. | Pads cannot compensate for unknown voids or inadequate ground. |
| Truck condition | Follow level, sector and transport-to-work setup requirements. | An unlevel or incorrectly configured truck is outside the assumed chart condition. |
Estimate average pressure beneath an outrigger pad
A qualified planner can compare this average pressure with verified ground capacity. The calculation alone does not approve the setup.
The illustrative average pressure is 240 kPa. A planner must still address load distribution, pad stiffness, soil variability, voids and the applicable design method.
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| Step | Calculation or condition | Result |
|---|---|---|
| Average support pressure | 120 ÷ 0.50 | 240 kPa |
| Ground comparison | Allowable ground pressure ≥ calculated design pressure | Qualified check required |
| Setup confirmation | Actual pad, ground, slope and outrigger geometry match assumptions | Required before work |
- Manufacturer or engineering reaction: 120 kN at one support for the defined case
- Effective support area: 0.50 m²
- Verified ground bearing capacity: Required from a qualified assessment
Do not use this simplified division to approve a crane setup. Manufacturer data and qualified ground assessment remain controlling.
Put site constraints in the purchase brief
Record the required reach, available outrigger space and known ground or slope constraints. Ask the qualified parties to establish support reactions and the applicable setup. This page supplies no ground-bearing calculation and no approval for a particular site.
Information to prepare for this review
- Load and maximum required radius
- Lift sector around the truck
- Outrigger extension and available space
- Ground bearing information and support method
- Slope, level and access condition
- Wind and other manufacturer operating limits
Records to request and keep
- Manufacturer chart and setup instructions
- Site and lift geometry record
- Ground-support assessment by qualified persons
- Outrigger, interlock and level-system inspection
Common mistakes and what to check instead
- Assuming full outriggers guarantee stability: Verify ground, level, radius, sector and chart condition together.
- Measuring radius from the truck edge: Use the manufacturer-defined crane reference.
- Using makeshift support on unknown ground: Use a qualified ground and support assessment.
Scope of this guide
This page does not calculate ground bearing pressure or approve a setup.
Qualified lift planning and the manufacturer instructions control.
Stop work for unknown ground, incomplete deployment, excessive slope, failed interlocks, unverified radius or any condition outside the chart.
Sources and applicability
Controls the project-input, quotation, approval and inspection workflow described in this guide.
Provides public checklists and worksheets; the signed project documents remain controlling.
Defines the relevant product family and published configuration boundaries. Project-specific ratings require the selected OEM documents.
Official U.S. reference supporting configuration-specific load charts, stability factors, inspection identity and removal of hazardous deficiencies. Local rules may differ.