The Case of the Injured Pole Dancer
While in service, the threads of a temporary, dancer pole failed. The sharp edges of the fractured pole and failed threads severely lacerated the performer’s arms and torso. The remnant pole and threads were metallurgically assessed. The manufacturer’s installation instructions, operation instructions, and maintenance instructions supplied to the consumer were inadequate.
U.S. regulatory safety standards for threaded products were consistent with the U.S. Consumer Product Safety Commission guidelines and American Society for Testing and Materials (ASTM) Standards. There were vague descriptions in the installation instructions about threaded parts, operation and maintenance of gymnastic / fitness equipment. The sharp internal radius in a thread root initiated the fatigue failure and resulted in a circumferential crack in the transverse plane of the pipe. The material thickness at the root of the pipe thread was 0.025”. The threads failed in buckling and shear as a result of eccentric loads.
Safety signage, labels, “Cautions” and “Warnings” were not with the threaded pole. The torque requirements for the adjustable jack screw and pole threads were not provided to indicate periodic validation by specific measurements. There was not a maintenance checklist for the threaded components, pole straightness, pole wobble, thread deformation or inspections for cracks in metal parts. The useful product service life was considered to be catastrophic failure.
The Lessons Learned:
The pole by design was a semi-permanent/temporary apparatus for intermittent usage. There were cracks, impact fracture surfaces and fatigue striations in the threads. The manufacturer’s installation, operation, and maintenance instructions were inadequate. The owner and performer had mutual responsibilities for “permanent” equipment installations intended for constant use and routine validation for structural integrity.