![]() ![]() It shows what the elevation of the boom point is so it can be quickly determined if a load (say a tall vessel) can be erected with a certain boom length. This comes in really useful when making a quick crane assessment.Ĭolumn 4 is even more useful. It shows that if this boom of 70 feet needs to work at a 30 foot radius then the boom is at an angle of 67.9 degrees. Instead I want to draw attention to column 3 and 4 of the partial chart in Figure 2, as this chart contains information that many modern charts omit.Ĭolumn 1 shows the boom length of 70 feetĬolumn 3 is helpful in the phase where the crane size or required boom length is to be determined. Instead, these charts contain a substantial amount of written information (that we will not analyse in this article). These cranes have been around since the late 1960s and in that time the charts were not decorated with the pictograms that are presently experienced as normal and useful. The second crane is a 150 tonne capacity Manitowoc crawler crane model 4000W (see a partial chart in Figure 2). The chart is applicable for a full 360 degrees and the outriggers are extended by 50 %. In addition, the crane has 5.5 tons of counterweight (the crane carries its counterweight when it travels). This capacity is at 85 per cent of its tipping capacity. The radius and boom length combination result in a capacity. ![]() Capacity charts don’t get any simpler than this. The first is a 45 tonne Grove hydraulic rough terrain crane model RT650 (see a partial chart in Figure 1). Let’s have a look at three different load charts, the information they contain, and how the complexity of the chart increases with the capacity of the crane. However, this doesn’t always make the chart easy to read. When comparing such cranes, the correct chart interpretation is very important (as it always is with every crane chart).Īlthough almost every crane chart nowadays meets the ISO and-or the ANSI requirements, manufacturers try (with good intensions) to include as much information as possible in a crane chart to make the document as comprehensive as possible. Some of these cranes still measure the radius from the centre of the ring, while others measure the radius from the mast foot or boom hinge point. Mammoet, Sarens, ALE and Bigge are examples of such companies. These are almost exclusively designed and built in-house by the end users. Then there are the ring cranes without a base machine at the centre of the ring. For crane types where the main machine or base crane is mounted inside a ring, for example, the Manitowoc M4600 Ringer and the M-1200 Ringer, the radius measurement still holds true: from the centre of rotation of the crane to the centre line of the hook block. ![]() For cranes on crawlers and outriggers this means that the radius can never be (near) zero as the physical dimensions of the crane prevent this. The radius is measured from the crane’s centre of rotation (the centre of the slew ring) to the point where the centre line of the hook block touches the ground. The big picture, however, always remains the same: a load chart shows the boom length and how much that crane can lift (its capacity) with that boom length at a certain radius. Even when a crane chart is present in the crane it can be a daunting task to analyse (or decipher) it. However, unfortunately, we do not live in a perfect world. ![]() Without it, a crane should simply not be operated.Īnd if we lived in a perfect world this would indeed be the case. The title of this article may come as a bit of a surprise to those of you expecting a technical article on advanced crane physics this is because a capacity chart (or load chart) really is the most basic crane document. ![]()
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