US Navy tells staff to tighten hoist covers

The Navy found that the failure was caused by a loose inspection cover on the hoist.

"This limit switch uses an l-shaped bar that prevents the traveling nuts from spinning on the shaft by lodging into grooves on the travelling nut and instead forces the nuts to travel along the shaft to engage the contacts," the Navy said in a recent issue of its Crane Corner bulletin. "This L-shaped bar is held in place by the inspection cover. The EW series limit switch is used on a number of Yale hoist models and is similar to the series CE limit switch that may have the same problem.

"Further investigation revealed that the cover plate was not tightly secured which allowed the L shaped bar to disengage from the traveling nuts. With the traveling nuts spinning on the shaft rather than traveling along it, the contacts were not engaged and the limit switch did not stop the motion of the hoist."