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Collapse of Crane

On July 18, 2008, one of the largest land-based cranes in the world collapsed in a

Houston, Texas refinery resulting in four fatalities, damage to an adjacent tank, andsignificant delays for a planned coker unit turnaround.

The maximum lift capacity of this crane was 2,500 tons. The crane operators were inthe process of aligning pendant lines from the crane mast for connection to theauxiliary counterweight platform. During this activity, the crane boom was raised toohigh vertically, allowing the boom to go into an overhaul condition which caused theboom to fall backwards. An overhaul condition results when the forces that keep theboom in a stable position are exceeded, resulting in negative forces that physicallypull the boom backwards, resulting in a crane failure.

Becht Engineering was selected to determine the critical boom angle and boomradius that would result in an overhaul condition based on: (a) a theoretical analysisof the physical crane force exerted on the boom, and (b) an evaluation of thesecurity camera photographs which had captured pictures of the crane boom at themoment of the collapse.

Charles Becht V was selected to conduct the theoretical physical evaluation andChad Morris, PLS was selected to work with a Becht Engineering subcontractor for

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the analysis of the security photographs. Harry Costner, PE was selected as theoverall Project Manager for Becht Engineering.

The theoretical analysis by Charles Becht V required the review and evaluation of over 100 crane drawings from the crane vendor. Several analytical methods wereconsidered for this theoretical determination. The final method selected was todevelop a free body diagram approach that modeled the crane mast, crane boom,main suspension system, and auxiliary suspension system. Due to the manyvariables involved with such an evaluation, a total of nine separate cases wereanalyzed. At the conclusion of this study, a single case was selected as the mostlikely case that would cause the overhaul condition. The results of this studypredicted that the boom would reach a point of overhaul instability at a radius of 97.1ft. and a resulting vertical angle measured from the horizontal of 77.4 degrees.

The analysis of the security camera photographs was conducted with the utilizationof laser surveying, 3D modeling, and Image Analysis technology software andhardware. Under the leadership of Chad Morris, PLS, a number of security cameraimages were evaluated to produce the final conclusions. This study concluded thatthe boom was starting to fall backwards when the vertical boom angle as measuredfrom the horizontal was 77.6 degrees and the boom radius was 95.7 ft.

The Becht Engineering team was highly pleased with the extremely close alignmentbetween the theoretical calculations and the actual results from the security cameraimage calculation. The Client, who was the refinery operator, also expressed a highdegree of satisfaction with the close alignment of the two independent study results.It is worth noting that the crane chart predicted the overhaul boom radius to be at120 feet.

The conclusion of this study highlights the significant analytical capabilities of theBecht Engineering technical staff and their ability to address very complex topics in arelatively short period of time. The Client was highly appreciative of Bechts effortsand has been giving specific credit, in public speaking engagements about the cranefailure, to Becht Engineering for this work.

Becht Engineering Co. has recognized the need to carefully review a detailederection procedure for the critical processes in large crane assembly andknockdown. Ground bearing pressures and boom clearances for the assemblycranes need to be assessed. In many assemblies the large cranes computers mustbe manually overridden during the erection processes to accommodate masterection or boom jib assembly initial lift-off and Becht wants to monitor theseoverride situations and the cancellation of the override process. Backward or sidestability must be studied to determine boom, mast or counterweight limits. Mostcrane manufacturers provide detailed assembly instructions in their parts andservice manuals but rarely are these documents shared with the end user.Commonly, the vendors field erection personnel have access to these documents

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but they are often reluctant to share massive manuals in whole or part with the enduser. These manuals rarely specify recommended rigging for outlined tasks andweights must often be determined by consulting various documents and sources. Itis Bechts belief that a reviewer must have full access to all documents from themanufacturer to fully assess a Safety Execution Plan (SEP) or Safety Action Plan(SAP).

Becht Engineering Heavy Lift Operations Professionals are actively participating inreviewing critical assembly documents and are requesting first hand review of manufacturers documents to verify procedural integrity. We are runningindependent analysis of rigging requirements and soil mitigation matting plans. Incritical phases Becht is questioning crane stability limitations and monitoring actionplans to ensure safety. Support crane capacities are studied on assembly loads andmultiple crane lifts (common in Mast and Super Lift assemblies) are studied todetermine possible load transfers between cranes as booms and masts are

jackknifed into working positions. Following assembly, with most floating super liftcounterweights there is a critical balance point where too little counterweight resultsin dangerously critical high chart percentages and too much counterweight cannotbe floated by the load and swinging is prevented. Becht Lift Experts are dedicated infinding the perfect balance between safety and efficiency in lifting and offering thatadvice to the customer.