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to the Club, the crane housing detachedfrom the platform and the crane operatorlost his life. Investigations are still under

way but we note that there are severalfactors, such as poor maintenance, over-loading and improper use, faulty designand latent defects, which may contribute

to a slewing bearing failure. Greasing routines and tilting clearance

measurements (or axial reduction measure-ments) must always be followed strictly inaccordance with the makers instructions.Beyond this we would also recommendcarrying out analysis of the used slewingbearing grease every six month, or at a timeinterval appropriate to the usage of thecrane. If carried out in a controlled man-ner, the used grease analysis is probably themost cost effective and reliable monitoringmethod for slewing bearings. The bearingmakers, the grease suppliers or your clas-sication society can usually provide moredetailed advice with regard to inspectionintervals, test methods and evaluation ofthe result.

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Loss PreventionThe Swedish Club Letter 12005

Are you fully aware of the designcriteria for your ships cranes? Were thecranes designed for hook duty only? Canthey be used in unsheltered conditions

without restrictions?The Safe Working Load (SWL) mark-

ing on a crane jib indicates the maximumpermissible load in the hook. Cranes are regu-larly tested to ensure that the SWL actually is

a safe load. This is a minimum requirementdened by the International Labor Organiza-tion (ILO).

The life time of a crane has often very lit-tle to do with the SWL marking and is basedupon a spectrum with different loads in thehook. When a general cargo crane operates

with grab it will nearly always be with full grab which means a load spectrum with maximumload. A crane working in unsheltered condi-tions will be exposed to shock loads. These

working conditions will greatly reduce the life-time of the crane unless the SWL is adjusted

accordingly. There is also a risk of overloadingelectrica l motors and generators. The oil cool-ing capacity may also be insufcient. Detailed information about the design cri-

teria and load limitations for the cranes can

KNOWGet to

Peter StlbergDirector Technical & Loss Prevention

always be found in the makers documenta-tion. It is advisable to study it carefully andensure that the crew has good knowledge.

If the crane is classed, details about opera-tional approval limitations may be foundin the crane certicate appendices. Weunderstand that this information has beenintroduced during the last few years.

With a view of avoiding off-hire situationsand disputes, ensure that charters are ful lyaware of any operational limitation of thecranes. It is good practice to include this in-formation in the Ship Details appendices.

Slewing bearing failures on turret cranes

The slew bearing, which is a main structuralload-bearing device that attaches the crane tothe platform, is a potential source for cata-strophic failure. In the severest case reported

yourgear!

P H OT O : T H E S WE D I S H C L U B