Crane Failure in Arizona and Lessons for Safe Rigging

[MikePhua]

The Incident and Mechanical Breakdown
In a residential neighborhood in Chandler, Arizona, a crane operated by a tree care company suffered a catastrophic failure during a tree removal operation. The boom collapsed after lifting a section of tree that exceeded the crane’s rated capacity. Upon impact with the ground, the boom cylinder detached, and the boom rest landed near the top of the structure. The front of the crane tipped backward, flipping the carrier and rendering the machine unusable. Miraculously, only one person was injured, though the outcome could have been fatal.
This event highlights the dangers of overloading and improper setup, especially in urban environments where space constraints and public safety are critical. The crane, likely a boom truck rather than a full-fledged hydraulic crane, was operating without adequate dunnage or outrigger support. Only one outrigger pan was visible, and there was no caution tape or signage to secure the work zone.
Boom Trucks and Misclassification Risks
Boom trucks are often mistaken for cranes due to their lifting capabilities, but they lack the structural redundancy and stability systems of purpose-built mobile cranes. A boom truck typically consists of a telescoping boom mounted on a commercial truck chassis, used for light lifting tasks. However, when used for tree removal or construction, they are frequently pushed beyond their design limits.
The media often mislabels such incidents as “crane disasters,” contributing to public confusion. In reality, many of these machines are improperly classified and operated without adherence to ANSI or OSHA standards. This misrepresentation can obscure the root causes of accidents and hinder regulatory enforcement.
Load Charts and Weight Estimation Challenges
Tree removal presents unique rigging challenges. Unlike steel beams or concrete panels, tree limbs vary in density, moisture content, and internal defects. Estimating weight accurately requires experience and reference to green log weight charts, which are mandated in some states. ANSI standards require that the climber, operator, and ground crew have access to these charts before beginning work.
In this case, the crew attempted to lift a large section of tree in one piece, likely to expedite road clearance. The limb’s weight exceeded the crane’s capacity, causing structural failure. A more cautious approach would have involved sectional cuts and staged lifts using a larger crane, such as a 50-ton or 75-ton hydraulic unit.
Structural Failure and Shock Loading
When a crane lifts a load that exceeds its rated capacity, the boom and hydraulic components experience shock loading—a sudden force spike that can exceed design tolerances. This can cause:

• Boom cylinder detachment
  
• Frame distortion
  
• Outrigger pad failure
  
• Carrier tipping
  

Shock loading is especially dangerous when the boom is extended and the load is lifted over the rear of the crane, as was the case in Arizona. The center of gravity shifts rapidly, and without proper counterbalance, the entire machine can flip.
Operator Training and Risk Awareness
Crane operators working with tree care companies face elevated risks due to unpredictable load shapes and weights. Tree work ranks among the top five deadliest occupations in the United States, surpassing firefighting and law enforcement. Crane operators hired by inexperienced crews are often exposed to unsafe rigging practices and poor communication.
Best practices include:

• Using cranes rated for at least 50 tons in tree removal
  
• Conducting pre-lift meetings with all crew members
  
• Verifying load charts and boom angles
  
• Ensuring proper outrigger deployment and ground support
  
• Avoiding lifts over public roads without permits and barricades
  

In one case from Missouri, a crane operator refused to lift a tree section without a certified arborist’s weight estimate. The crew initially resisted, but after recalculating, they discovered the limb weighed nearly double their assumption. The lift was rescheduled with a larger crane, preventing a potential accident.
Equipment History and Manufacturer Notes
Boom trucks gained popularity in the 1970s and 1980s as cost-effective lifting solutions for utility and light construction work. Manufacturers like Terex, Manitex, and National Crane produced thousands of units annually. However, these machines were never intended for heavy-duty rigging or dynamic loads like tree limbs.
Hydraulic cranes, such as those made by Grove, Liebherr, and Manitowoc, offer better stability, load monitoring systems, and operator feedback. These machines are equipped with Load Moment Indicators (LMI), which alert the operator when approaching tipping thresholds. Retrofitting LMIs on older boom trucks is possible but rarely done due to cost.
Recommendations for Tree Removal Operations
To improve safety in tree-related crane work:

• Use certified arborists to estimate limb weights
  
• Employ cranes with LMIs and rated load charts
  
• Avoid boom trucks for complex lifts
  
• Train climbers and operators in ANSI Z133 standards
  
• Maintain clear communication between ground crew and operator
  

Tree removal should be treated as a specialized lifting operation, not a routine task. The combination of unpredictable loads, urban settings, and public exposure demands rigorous planning and equipment selection.
Conclusion
The crane failure in Arizona serves as a stark reminder of the consequences of overloading, poor setup, and miscommunication. While the operator survived, the machine was destroyed, and the incident could have been fatal. By respecting load limits, using proper equipment, and adhering to safety standards, crane operators and tree crews can prevent such disasters and protect lives. In the world of rigging, precision and caution are not optional—they are the foundation of every safe lift.