A 20 ton polar crane motor fell during a 3400 kg (7500 lb) lift, narrowly missing personnel working beneath the crane. Witnesses reported that the motor fall was preceded by a falling oil mass, and it was believed that the motor was intact prior to impact. The maintenance history of the crane showed that the motor had been removed, repaired, and reinstalled 2 years prior to the failure. Observations of oil leakage were noted yearly up to the failure. The motor casing was held onto the adapter plate by eight 14-20 UNC x 25 mm (1 in.) long hex...
Carl J. Czajkowski, Failure of a 20 Ton Polar Crane Motor by Bolt Fatigue, Handbook of Case Histories in Failure Analysis, Vol 1, Edited By Khlefa A. Esaklul, ASM International, 1992, p 308–312, https://doi.org/10.31399/asm.fach.v01.c9001095
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