A failed weld on a repaired slewing ring bearing is being blamed as the immediate cause for the deadly collapse of a construction crane in New York City a year ago.

Two men, Ramadan Kurtaj and Donald Leo, died in the collapse on May 30, 2008. When the slewing ring bearing apparently failed, the cab and boom separated from the top of the 20-story mast. The assembly fell all 20 stories, raking an adjacent building and down into the street below.

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Federal investigators have reportedly tied the accident to improperly welded repairs made by RTR Bearing (China; website) a year earlier, in July 2007.

In May 2007, the crane, an older model Kodiak, was struck by lightning. Shortly after that, workers reportedly noticed daylight through the cab and boom's supporting turntable. Further inspection revealed a two-foot crack in the slewing ring bearing. At that point, turntable and slewing bearing were removed for repair. Another turntable and bearing were installed temporarily, so the crane could remain in service.

Avon Bearings (USA; now a division of Kaydon Corp., USA) bid on the repair, quoting just over $120,000 and 28 weeks lead time. Avon's bid was rejected.

RTR Bearing Company Ltd., a slewing ring bearing manufacturer based in Luoyang, China, bid $20,000 with a much shorter lead time.

Several emails have now been made public, indicating even before the contract was awarded, RTR told New York Crane it was uncertain if it could make the repairs properly. An RTR representative emailed New York Crane on June 7, 2007, saying: "And honest speaking we dont have confidence on this welding."

New York Crane awarded the bearing repair contract to RTR anyway.

The bearing was removed from the crane, shipped to China, repaired by RTR, and shipped back to New Jersey. There, it was assembled and additional repairs were made to the turntable assembly. Finally, the crane's temporary bearing and turntable assembly was removed and the repaired assembly put in place.

The crane's repairs were approved by Michael Carbone, chief inspector of cranes and derricks for the City of New York. Mr. Carbone was a former employee of New York Crane and Equipment.

This was the second deadly collapse in 2-1/2 weeks of cranes owned by New York Crane and Equipment, safety inspections and installations approved by Mr. Carbone. The first crane collapse killed seven people. Mr. Carbone resigned in July 2008, a month after this collapse.

In addition to the failed slewing ring bearing, the possibility the crane was pressed into service beyond its service life has also become a question.