Detective Work on Cranes
“Each piece of lifting equipment or component has been designed with an intended design life making it crucial that such equipment should be regularly checked for its lifespan condition as early detection of signs of deterioration can prevent failures and extend service life. It is also an essential part of making sure operations continue safely and that regulatory compliance is met, says Ian Grobler, Sales Manager for Konecranes South Africa.
The Konecranes Design Life Analysis has been specifically formulated to calculate the remaining design life of structures and machineries of cranes and associated lifting components. It determines the amount of work that can safely be performed before its useful life is over.
While frequent inspections are necessary, they cannot always catch machinery failure that may be caused, for example, by extremely fast crack propagation. Operator behaviour and misuse of lifting equipment can also play a major role in the shortening of the lifespan of hoists, slings, and cranes. Even well-designed equipment can fail early if not used correctly.
Equally important
Ian elaborates, “Ascertaining lifting equipment lifespan is not only about cranes, it is equally important to inspect the lifespan of hoists, slings and other small components as their performance is just as critical in any lifting operation. These components don’t have a fixed expiry date and their lifespan depends heavily on usage, environment and maintenance.”
Cranes are designed from a fatigue point of view. The first consideration is the class of utilisation which will determine the frequency with which a load will be lifted, and how many hours the machinery will be in service during the lifetime of the crane. It is then determined the kinds of loads the crane will handle and at what capacities.
Design phase
As these are only estimations during the design phase, this is where the detective work occurs in the Design Life Analysis. Through production and service records, process observations and operator interviews, a qualified and trained inspector researches how many actual cycles the crane has performed, how many loads it has handled and at what capacity in order to form a calculation of its current remaining design life.
A calculation of design life can supply the information and data needed to help assess safe working limits The analysis will include design life calculations, conclusions and recommendations for any needed actions to continue the safe use of the crane or component.
Fatigue differently
Crane structures and their various accessories fatigue differently, and at different rates. Structures consume their design life in work cycles, while other elements may consume their design life in running hours. A girder is stressed only once per stress cycle and therefore the propagation of fatigue is relatively slow. Even if a fatigue crack does appear, the rate of failure is usually measured in years.
Rotating machineries are different. Working constantly under loaded conditions, their components may be stressed tens of thousands of times during one movement. When a crack forms in these components, it can become critical within hours or days.
Not enough for compliance
Konecranes Design Life Analysis fulfils the requirements of a yearly design life calculation as required by ISO-12482-2014 and AS 2550.1:2011. Ian adds, “It also forms part of the South African regulatory key inspection guidelines of every 12 months, which is typically performed alongside the 12-month inspection to assess the “Design Working Period” (DWP) for both structural and machinery components.
“Simply conducting an annual load test is not enough for compliance. The Konecranes Design Life Analysis enables the customer to plan timely modernisations, component repairs/replacements and general overhauls which can reduce operational costs and safely extend the life of the lifting equipment as well as help eliminate any potential on-site failures and injuries to operators” concluded Grobler.
