Heinz-Gert Kessel and Carsten Bohnenkamp (Cranes Today February p58) illustrate the problems with tonne-metre ratings. Kessel’s explanation, while clearly and properly presented, would be very confusing to anyone trying to decide which crane to use. Bohnenkamp has it right: The only way to determine the right crane for the job is to look at the load charts and associated data. Tonne-metre ratings give you the result of two factors and while both are required to determine which crane or configuration to use for your project, neither can be determined from the tonne-metre rating. Load charts provide all the required data for all parties concerned. Potential clients do not ask you whether you have a crane with a particular tonne-metre rating. They ask you for a particular capacity and want to see the load charts. 

Bryan Pepin-Donat, director, contracts/international business,
Lampson International