Crane Institute of America

Master Link or Hook: How Likely to Falter?

Killed – two workers in California when their personnel basket fell nearly 80 feet.

OSHA has strict requirements regarding hoisting personnel. If these requirements are followed, such accidents should cease to happen. The actual cause of this particular accident is still unknown to the public as the OSHA report will take time to surface. Early speculation is that the hook failed or the basket came off the hook.

Hooks used in personnel hoisting operations “must be capable of supporting, without failure, at least five times the maximum intended load applied” according to OSHA 29 CFR 1926.1431(g)(3). In simple terms the hook will withstand a 500% overload before it will fail at which point it will bend, not break. On a crane as large as the one used in the operation, the weight of the heaviest personnel basket and its contents should not come close to the yield point of the hook.

This begs the other question, how could the master link for the bridle supporting the basket come off the hook?

OSHA requires hooks used for hoisting personnel “must be of a type that can be closed and locked” (1926.1431(g)(1)(i)(A)). Closing the hook’s throat would prevent the basket from coming off the hook. Now let’s assume the hook was not equipped with a latch or the latch was defective.

  1. The weight of the basket should keep the master link in place in the bowl of the hook.
  2. For the basket to come off, an upward force would have to be placed on the master link. This could cause the master link to slip over the hook tip.
  3. An upward force could be generated by hitting an object with the personnel basket.

Purchase Mobile Cranes and Rigging handbook set by Jim Headely and read more about Hoisting Personnel.

Resources: San Francisco Chronicle, Cox Media Group.