Safety alert for building maintenance units and suspended scaffold cradles

A safety alert has been issued to remind owners and users of building maintenance units (BMUs) and suspended scaffolds of the need for ongoing inspection of critical components.

The alert from Work Cover NSW was issued following a recent incident in October where two workers were seriously injured when the BMU cradle they were working in fell 10 storeys onto an awning below.

Work Cover said initial investigations indicated the cause of the collapse was a failure of the connection between the winch and the cradle.

This connection used a single bolt, loaded primarily in tension, at each of the two winches; and it is believed one of these bolts failed, causing a sudden transfer of load to the bolt at the other end, which then also failed.

The bolts are hidden within the connection and cannot be inspected without the connection being disassembled.

Inspections revealed that both bolts showed signs of significant fatigue cracking which would have weakened the bolts, resulting eventually in the sudden failure without obvious external warning signs.

A similar incident in 2009, which resulted in the death of one worker and serious injury to another, was due to the failure of a simpler connection on a suspended scaffold cradle from undetected fatigue cracks.

Action required

Work Cover advises that BMU and suspended scaffold cradle owners must:

• identify critical components in BMUs or scaffold cradles — eg, where failure of a component would risk the safety of anyone in the vicinity of the BMU or suspended scaffold;
• assess whether the current inspection and maintenance program adequately deals with these critical components, especially any components that need disassembly to inspect;
• upgrade the inspection and maintenance program if necessary;
• include non-destructive testing or regular replacement of components as part of the program where visual inspection alone is not adequate to detect potential developing defects, such as fatigue cracks;
• carry out a major inspection on any BMU that is over 10 years old and has not yet had a major inspection;
• carry out a major inspection on any BMU that has had a major inspection, which is overdue for its next recommended major inspection, or five years after the last major inspection where no recommendation was given.

For further information, go to: Australian Standard AS 2550.13-1997 Cranes – Safe use Part 13: Building maintenance units.

Source