A production building was being constructed at a cement plant. A large crawler crane was being used to install the pre-assembled metal wall framing of the building. The weights and lift radii of the four wall framing sections, along with the rigging spreader and other lift equipment, were within the rated capacity of the crane. (more…)
The boom of a hydraulic crane was bent while removing temporary sheet piles at a construction site. A vibratory hammer had been placed at the top of the sheet piles to both drive and remove the piles. The vibratory pile driving placed no significant loads on the crane boom, as that operation relied on the weight of the sheet piles and the vibration of the hammer to sink the piles into the soil. The vibration of the hammer and the lifting force of the crane boom were needed to remove the sheet piles from the soil. (more…)
Mobile cranes depend on stability through their outriggers. These are the four “legs” that are deployed onto soil or other working surfaces adjacent to the crane. When a mobile crane is set up at a site, the outriggers are deployed by a hydraulic mechanism that extends the four outriggers beyond the crane body and then jack the crane free of its wheels so that it is supported by the outriggers only. (more…)
The operation of many cranes is a balancing act — one very similar to the childhood experience of using a playground seesaw. When the equipment isn’t properly balanced, the crane may succumb to the tipping force and fall to one side. Such a tipover is more common in mobile cranes rather than fixed-tower cranes.
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Defects that cause problems in machines are categorized into two different concepts. Manufacturing defect is a term that applies to a situation where the defect was unintended. For example, a part was installed that did not meet the designer’s specifications or quality. A design defect is another matter. Design defect is a term that applies to a situation where the defect resulted from a purposeful decision or by failing to investigate or heed available design criteria on the part of a designer or builder. (more…)
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