rruggle, I think you have missed the point of this story—the information here is the result of countless hours of research, interviewing experts, consulting with engineers and studying load charts. The figures here are reasonable. Anyone writing a story like this would have to make a decision how to standardize the ratings of these cranes. Many of them were rated in metric, so it made sense to stick with metric. Certainly, I could have rounded further, but saw no need to do so, and no experts I consulted in researching this story suggested I do so (and I had many discussions with experts about the metric conversions). In addition, it would be risky for crane personnel in the field to arbitrarily round up or down when dealing with crane ratings. Users should always consult the manufacturer if there is any question about the rated capacity.

Thank you Mr Vanhampton for an article I consider one of the more solid articles
appearing in ENR. I do appreciate the work you put into the article.

It is the translation of 2500 in one system of units to 2268 in another system of units
I object to. I would round 2268 to 2300 so there would not be spurious accuracy. More
importantly with fewer digits there is a lot less chance of getting the number wrong and
here any transposition error is on the side of danger eg 2628 for 2268.

If concern is felt that 2300 is larger than 2268 perhaps a standard can be written so there
is rounding down ( the official name for this is truncation and truncation has the additional
benefit that it is less error prone than rounding).

Flatly put, not too diplomatically put, all the experts you consulted on the conversions
are wrong. My guess is that they just did not give the matter the attention it deserves.

Again I want to thank you for a very worthwhile article.

Sorry rruggie, it appears to me that you are making an unverified assumption. Not all zeros are insignificant, and just because a crane’s capacity is named to a rating of so many hundreds of tons, that does not mean that it was rounded to the nearest 100. In fact, a load limit is both an engineering and a legal/liability requirement. The manufacturer has already incorporated various factors of safety, and if for a particular arrangement, a manufacturer says the limit is 2500 tons, and you have a load that is known to within the ounce (+0 to – 1 oz) to be 2500 tons, the manufacturer is essentially guaranteeing that you can lift that load (all the other disclaimers notwithstanding, of course). The real capacity of the crane is, of course, something greater, and not perfectly well-known. If the crane failed on that lift, the manufacturer could not later claim that the capacity was 2500 + or – 50 tons, and this must have been one of the 2450 ton units, so it’s not our fault! Similarly, if you measured the load to exactly 2267.96 tonnes, yes, you could be sure that the crane would lift the load, again, because the actual capacity is greater and the load limit includes a factor of safety that allows the manufacturer to guarantee that capacity.

Since the load limit is essentially a guarantee, or a safety limit, it appears to me that the limitations on the limit are the accuracy of the field measurements of load amount, lift radius, and similar factors. In this case, the comparison numbers are assigned, not measured, so they have no inaccuracy. You may argue that no one will measure the loads that accurately in the field, but that does not make the rating comparisons wrong. In theory, and I believe in fact, they are as accurate as your field measurements, and different applications will have different accuracies in the field.