CRANE CRITIQUE
This month’s topic: Tower Crane’s erection and inspection rules. A monthly crane and rigging informative column for all personnel directly or indirectly involved with crane safety. Each month we will attempt to explain a different technical issue pertaining to crane operations here on Guam, addressing the sometimes over-looked or misunderstood topics by management and operators alike. By Dave Barnhouse The latest revision to the ASME B30.3 standard for tower cranes contains significant changes that affect how engineers should take into account wind loading on jobsites, including those prone to typhoons. The standard also calls for more rigorous inspections than in the past, now requiring a major teardown and rebuild every five years. Tower cranes now must be engineered to withstand wind conditions detailed in ASCE 7, the American Society of Civil Engineers' standard on minimum de-sign loads for buildings and other structures; it was previously a recommendation. The volume specifies that ASCE 7 wind speeds must be used for calculating foundations and freestanding heights. Even though the latest version of ASME B30.3 was released in 2012, many people are still not aware of the changes. Operationally, manufacturers and crane suppliers, such as rental companies, typically advise users on how to pre-pare for windy conditions, including typhoons. Operators generally are ad-vised to "weathervane" a tower crane, or unlock the swing brake, so its rotating structure can spin freely in the wind. According to the ASME B30.3-2012 document, the site supervisor and lift director are responsible for ensuring that weather or other adverse conditions are addressed in each lift. Major inspections are, for the first time, also included in the new standard. The new inspection category calls for components such as drive systems, motors and gearboxes to be disassembled and, if necessary, rebuilt at 60-month intervals or as specified by the manufacturer. This practice, experts say, is important because some critical components are not visible during a crane's frequent (daily) or periodic (annual) inspection.
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Liebherr 22 ton tower crane at Navy Hospital Like the wind standard, the major inspection aims to reduce risk by identifying potential failures. ASME Committee members felt that most of the maintenance issues on tower cranes, especially as they got older, were not keeping pace with the industry and what people in the industry were demanding for quality. Although it is not a requirement, the volume also recommends non-destructive testing of connection mate-rial, such as bolts and pins, during a major inspection. If you are doing a five-year inspection, it is not a bad idea to do a non-destructive test of all the bolts. (f) Inspections. (2) Pre-erection inspection. Before each crane component is erected, it must be inspected by a qualified person for damage or excessive wear.
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attention to components that will be difficult to inspect thor¬oughly during shift inspections. (ii) If the qualified person determines that a component is damaged or worn to the extent that it would create a safety hazard if used on the crane, that compo¬nent must not be erected on the crane unless it is repaired and, upon reinspection by the qualified person, found to no longer create a safety haz-ard. (iii) If the qualified person determines that, though not presently a safety haz-ard, the component needs to be moni-tored, the employer must ensure that the component is checked in the monthly inspections. Any such deter-mination must be documented, and the documentation must be available to any indi¬vidual who conducts a monthly inspection.
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