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Tower crane slew brakes
Key Issues:
Preventing catastrophic failure of tower cranes essential slew brake release
mechanism maintenance
Introduction:
HSE investigations into the collapse of two tower crane ibs has identi!ed that
there were problems with ade"uate maintenance of the slew brake release
mechanisms#
$he 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 ane%cient state& in e%cient working order and in good repair# $he emerging
!ndings from the HSE investigations indicate that the operational e%ciency was
compromised by lack of maintenance& in particular& insu%cient lubrication of the
slew brake release mechanism# $his alert provides supplementary information to
HSE Health and safety bulletin '() *+*,-. Preventing catastrophic failure of
lu%ng ib tower cranes in high winds#
/ackground:
$ower crane ibs 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 e%cient state#
'ailure 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#
$his could result in the ib or whole crane collapsing in strong winds#
0ction re"uired:
(wners and users of tower cranes should ensure that tower crane slew brake
release mechanisms are inspected and maintained in line with instructions issued
by the manufacturer# 1here crane manuals do not stipulate release mechanism
maintenance instructions the manufacturers should be asked to provide details#
Instruction should be provided to operators and maintenance personnel as to howslew brake release mechanisms should be checked& inspected and maintained#
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$his should include information& where necessary& as to the type of lubrication
and the fre"uency and method of applying lubrication to the release mechanism#
Supervisory checks should con!rm 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 $horough E2aminations should also con!rm the correct
function of the slew brake release mechanism#