Light cranes - laws and regulations

The crane's strength

Structural failure is not the only thing that must be avoided.

Unfortunately, we too often see suppliers disregard legislation and best practices for crane structures. The focus is frequently placed solely on avoiding structural failure—which can lead to permanent deformation and reduced load capacity. While avoiding such failures is obviously important, regulations also require that crane runway deformations remain within the limits set by standards.

Our experience shows that adequate documentation is often lacking; designing cranes based only on strength against structural failure is not enough to produce simple, slender, and inexpensive units. Steel is an elastic material—meaning it can bend to a certain point and then return to its original shape. 

To comply with Eurocode, the structure must be stronger to ensure it does not deform excessively during operation, even if it does not fail structurally.

Higher maintenance costs and downtime – NO THANKS!

An excessively flexible crane runway can easily cause problems - not only for the operator but also for the crane itself - leading to higher maintenance costs and downtime due to increased component wear (e.g., wheels and rails). Therefore, it is crucial to ensure that the forces generated during crane operation are correctly accounted for and modeled.

In most cases, deformation is the decisive factor in determining the size and design of crane runways and their supporting structures. This is an area where we often see issues with solutions provided by some suppliers. We always ensure that our solution complies with applicable regulations and delivers reliability that exceeds expectations.

Statement
“A column that is rigidly fixed at one end and subjected to a load at the opposite end will deflect eight times as much at the top under the same load if its height is doubled.”

Example
If a 2-meter column deflects 10 mm at the top under a given load, a 4-meter column will deflect 80 mm at the top under the same load.

Cranes and metal fatigue

Another often-overlooked factor is fatigue - specifically, metal fatigue. This phenomenon can occur when metal components are subjected to repeated stress during operation, leading to fatigue fractures, particularly in welded and bolted joints. It is therefore crucial to understand the forces generated - for instance, in a crane runway - when the crane travels along it. This allows joints to be designed and positioned correctly to minimize the stress to which they are subjected.

Failing to account for metal fatigue can result in high repair and maintenance costs throughout the crane's service life. In a worst-case scenario, a complete joint failure could lead to an accident. The extent to which the crane's structure flexes during operation influences fatigue. Eurocode outlines how to calculate this and determines whether such calculations are necessary. Unfortunately, many suppliers overlook these calculations; however, doing so requires, among other things, the ability to predict how the crane will be used over its entire lifespan. Few people can likely say what they will be lifting with their crane 20 to 25 years from now.

At CERTEX Danmark A/S, we are experts in all crane calculations, and fatigue is a factor we always take into account. Consequently, our crane solutions are optimized to last their entire service life with minimal service and maintenance costs.

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