CICA TECH CORNER
CICA ARTICULATED PICK AND CARRY CRANE SIDE SLOPE DERATION CALCULATION TOOL In the CICA Tech Corner article in the September/October 2020 issue, the CICA technical committee discussed the impact of changing ground conditions have on the operation of articulated pick and carry cranes. Since then, CICA, together with Multiplex, has developed an easy-to-use side slope deration calculation tool according to the manufacturer’s instructions to assist crane crews with their lift planning on site. WHY IS IT IMPORTANT TO CALCULATE the derated capacity of the articulated pick and carry crane when the crane is operating on the side slope? Crane load chart ratings are based on the machine being levelled in all directions. Mobile cranes operating on outriggers achieve levelling through adjusting the configuration of the crane outriggers, their load charts are designed to operate within the one per cent gradient (or 0.57°) ground slope. Articulated pick and carry cranes are not designed to operate on outriggers – any deviation to firm, level conditions could require the rated capacity to be reduced accordingly to the manufacturer’s recommendations. This is because when the crane is out-of-level, side loads develop in the boom. This side loading causes mobile cranes to lose capacity as the degree of out-of-level increases. Sometimes people are not aware that they are operating their pick and carry cranes on a side slope. For example, when operating the crane to lift and carry a load on site, if the crane drove on uneven road surface (potholes, etc.), the ground effectively creates a side slope condition. To prevent overloading the crane from these ground conditions, it is recommended that, before the lifting job starts, walk or drive around the site to confirm the lift path/route. How is the side slope deration calculated? As mentioned in the previous article, deration load charts 20 / CAL March/April 2022
are provided by manufacturers to guide the operator how to calculate the rated capacity reduction when a side slope is encountered. Crane operators follow the deration percentage specified on the chart to calculate the appropriate crane rated capacity for their lifting configuration and environment. SIDE SLOPE DERATION CALCULATION EXAMPLE A Franna AT-20 crane is selected
to perform a lifting task with the following configurations: • L ifting on winch • B oom length: 11m, load radius: 7m • A rticulation angle: 0°, straight ahead • G round slope 2° To calculate the rated capacity for this crane, the first step is to select the correct load chart and interpret the chart with the relevant crane configurations. This crane is intended to lift using the winch with 11m boom length, 7m radius at greater than 10° articulation. According to the chart, the rated capacity of the crane at this configuration is 3,750kg. The next step is to determine the deration percentage. The rated capacity obtained from the first step is for when the crane is operated on level ground (0.57°) – this crane www.cranesandlifting.com.au
