|Failed bolt connecting the winch and the cradle.|
BUILDING MAINTENANCE UNITS AND SUSPENDED SCAFFOLD CRADLES - Safety Alert | 06/11/2015 - This safety alert reminds owners and users of building maintenance units (BMUs) and suspended scaffolds of the need for ongoing inspection of critical components.
BACKGROUND: Two workers were seriously injured in October 2015 when the BMU cradle they were working in fell 10 storeys onto an awning below.
Initial investigations indicate 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. 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 show signs of significant fatigue cracking which would have weakened the bolts, resulting eventually in the sudden failure without obvious external warning signs.
In a similar incident in 2009 the failure of a simpler connection on a suspended scaffold cradle was also due to undetected fatigue cracks. It resulted in the death of one worker and serious injury to another.
|Suspended scaffold connection bracket failure showing fatigue cracks.|
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:
five years after the last major inspection where no recommendation was given.
Preliminary findings of window cleaners’ fall in October released: A Sydney window cleaner was injured after falling approximately four floors onto a balcony while cleaning windows on a hotel at Gloucester Street in The Rocks. The window cleaner, who was using rope-style window cleaning equipment, is reported to have suffered leg injuries in the fall.
SafeWork NSW is investigating the incident which comes as they release the preliminary findings of their investigation into an incident where two men fell approximately 10 storeys from a Sydney CBD building on Tuesday, 20 October. The men, who were harnessed, were cleaning windows on a 12 storey building on the corner of Pitt and Bridge Street in the city when the window cleaning cradle that they were working in suddenly fell to the awning below.
SafeWork NSW commenced an investigation into the incident which included sending the window cleaning cradle, known as a building maintenance unit, to SafeWork NSW’s TestSafe facility at Londonderry for testing and analysis.
The initial findings of the investigation indicate that the cause of the collapse was a failure of the connection between the winch and the cradle. The connection used a single bolt, loaded primarily in tension, at each of the two winches. It is believed one of the bolts failed, causing a sudden transfer of the load to the bolt at the other end, which then also failed. The bolts, which are hidden within the connection, cannot be inspected without the connection being disassembled.
Inspections revealed that both bolts showed signs of significant fatigue-related cracking which would have weakened them, resulting eventually in the sudden failure which occurred without warning.
In response to the findings, SafeWork NSW will undertake an awareness program and verification activities in early 2016 on buildings where Building Maintenance Units and Industrial Rope Access are used. SafeWork NSW Executive Director, Peter Dunphy urged all owners and users of building maintenance units and suspended scaffolds to inspect their equipment in the lead up to the verification visits.
“Operators should undertake regular inspections of building maintenance units and suspended scaffolds so that defects such as fatigue cracks are identified,” Mr Dunphy said. “They should also consider whether their current inspection and maintenance programs are adequate to prevent equipment failure in the future.
“A similar incident occurred in 2009 due to undetected fatigue cracks on a suspended scaffold which resulted in the death of one worker and serious injuries to another. “Fortunately, although the workers were seriously injured, they both survived, but the result could have been very different.”
SafeWork NSW has published a safety alert with guidance for owners and users of building maintenance units and suspended scaffolds on how to prevent similar incidents. Operators seeking further information on building maintenance units should refer to the Australian Standard.