HSE investigations into the collapse of two tower crane jibs has identified that there were problems with adequate maintenance of the slew brakes release mechanisms.
The purpose of this safety alert is to advise owners and users of steps to be taken to ensure that tower crane slew brake release mechanisms are maintained in an efficient state, in efficient working order and in good repair. The emerging findings from the HSE investigations indicate that the operational efficiency was compromised by lack of maintenance, in particular, insufficient lubrication of the slew brake release mechanism. This alert provides supplementary information to HSE Health and safety bulletin FOD 2-2014. Preventing catastrophic failure of luffing jib tower cranes in high winds.
Tower crane jibs are designed to free slew when out of service to avoid high loadings being placed on the crane structure and foundations with risk of failure or collapse. In order that a tower crane can be placed in the out of service condition it is essential that the slew brake release mechanism is maintained in an efficient state.
Failure to maintain the release mechanism can result in the operator being unable to fully release the slew brake when placing the crane in the out of service condition or the operator thinking that the slew brake is fully released when it is still partially engaged. If the brake is not fully released the upper slewing structure will not be able to slew freely in response to changing wind directions. This could result in the jib or whole crane collapsing in strong winds.
Owners and users of tower cranes should ensure that tower crane slew brake release mechanisms are inspected and maintained in line with instructions issued by the manufacturer. Where crane manuals do not stipulate release mechanism maintenance instructions the manufacturers should be asked to provide details.
Instruction should be provided to operators and maintenance personnel as to how slew brake release mechanisms should be checked, inspected and maintained. This should include information, where necessary, as to the type of lubrication and the frequency and method of applying lubrication to the release mechanism.
Supervisory checks should confirm that personnel are correctly carrying out their instructions and the crane is being placed in free slew when left out of service. Persons carrying out Thorough Examinations should also confirm the correct function of the slew brake release mechanism.
Safety Bulletin with thanks to HSE.gov.uk. Read full article here.