A structural failure leads to uncontrolled motion of a ‘Billy Pugh’ basket and injuries to crew

Four offshore personnel in the Gulf of Mexico were subject to uncontrolled motion while being transferred from a vessel to a production facility via the ‘Billy Pugh’ basket hoisted by a Titan model T5400B boom crane.

The boom began to swing due to the wind, and neither the swing brake lock nor attempts to reverse the swing stopped the uncontrolled motion.

The basket subsequently hit the railing on the vessel which caused injuries to three of the four offshore personnel.

Investigation determined that the crane’s hydraulic swing gear motor (slew drive system) had failed, which made it impossible to control the lateral movement of the boom. The mounting pad eye brackets that secured the swing gear drive housing to the crane cab base had sheared, allowing the housing to deflect under loading and the swing gears to disengage from each other. The disengaged swing gears prevented any control of swing motion and effectively disabled the crane during the personnel lift. The BSEE investigation concluded the following:

• The mounting bolts either backed out during operations due to vibration or other operational causes, or the bolts were never fully tightened to torque specification when the crane was installed.
  
  
• The loose bolts allowed the swing gear motor mount to deflect under loading, which put unplanned stresses on the pad eye mounting brackets until the brackets sheared.
  
  
• Inspection of these bolts for any loosening and to insure the proper torque setting is not a normal part of daily pre-use, quarterly, or annual inspection(s) of the crane.
  
  
• Abnormal movement of the swing gear motor under loading, resulting from failure of the securing bolts or mounting brackets, may only be detectable by personnel looking for that specific failure.