There are specific regulations for testing rollover protection structures for virtually every machine type. Within the EU, agricultural tractors are subject to Regulation (EU) No. 1322/2014 and similar regulations, while construction machines are subject to the machinery directive (Directive 2006/42/EC) and European standards such as EN 474. In terms of practical testing procedures for minimum requirements for rollover protective structures and falling object protective structures, these standards refer to the ISO standards 3471 and 3449, among others. Once cabins have passed the official tests, they are certified as “safety cabins”.
Ultimately, however, any successfully tested cabin can only perform the functions of a safety cabin in relation to a specific type of use, regardless of which regulations it was tested under.
Rollover protective structures for tractors must therefore be designed to ensure that the residual space of a driver restrained on the seat by a seatbelt is not restricted in case of a single rollover. For agricultural tractors, the energy to be absorbed is calculated on the basis of their unladen weight plus a safety margin based on the ratio between the tractor’s unladen weight and total permissible weight.
As a rule, heavy construction machines, in contrast to agricultural tractors, are fully equipped and do not tow additional implements. This is precisely the main advantage of agricultural tractors, which can be used as universal engines for any agricultural works on farms as well as related works beyond. These machines are appropriately subject to different regulations, and it is their total permissible weight that forms the basis for calculating the minimum required forces and energy to be absorbed by the protective structure in case of a rollover accident.
Once all parts of a test have been completed, the protective structure, that is the cabin, may only have suffered deformation within certain limits if the residual space is to be preserved. This always constitutes a challenge, as all aspects of testing need to be performed using a single cabin and no repairs are permitted throughout the course of the test.
The DLG Test Center operates two test benches, which allow it to carry out compliance testing on safety cabins of tractors and construction machines up to a total permissible weight or unladen weight of about 100 tons. Put in terms of force, these values correspond to 1500 kN of horizontal and 2000 kN of vertical forces that the Test Center can apply to structures.