How To Read A Spider Crane Load Chart


Spider crane load charts are used to calculate the weight of the load that a spider crane can handle. Here’s how to read spider crane lifting capacity!

Understanding what kind of load a spider crane can handle requires knowledge about a variety of different aspects. Not only is it important to understand what load the crane can carry, but also what the site looks, the ground conditions, and load requirements too.

Spider cranes are a popular choice of cranes for jobs that require a machine to go in and under and not up and over. Spider cranes can be folded up into relatively compact units and moved into place before unfolding its outriggers or legs into position, just like a spider.

There are critical aspects that specialists like UNIC and Concord Access Solutions need to follow when determining the size of the crane needed for a project; from site inspection to reading a spider crane load chart.

How to read a spider crane chart?

Let’s look at the key steps that take place first when specialists need to decide what size of spider crane is needed for a specific project or job.

Site Inspection

Specialists, like Concord Access Solutions, will always begin a project with a site inspection first. The site needs to be assessed for a few details including:

  • How would we get the crane in?
  • What is the width and length of the entrance or entry points?
  • Where does the load need to be accessed from?
  • Once in position, can we open out the outriggers to full extension?
  • Can the crane sit in its ideal position with all outriggers extended in order to lift the load safely?

Once this has been determined and the site has been declared safe and viable for a spider crane, the next step is to complete the due diligence on the ground type.

How to Read Spider Crane Lifting Capacity

Ground Type

Understanding the type of ground the spider crane will be sitting on is the next step in the process to understand if the ground type – whether it be a concrete slab or uneven gravel – will be able to carry the load of both the crane and its load together. It is technically known as understanding if the weight rating of the ground is sufficient.

Reading the Load Chart

Once it’s been established that the crane can access the site and the load, and that the ground can sufficiently carry it, it’s time to read the spider crane load chart to determine what load it can carry within the space requirements allowed.

Above is the example of the load chart for the UNIC URW-547 (4 tonne) machine. When reading the chart, you need to look at two ratio’s first:

Working Radius (m)

On the X-axis of the load chart is a variety of measurements in metres for the working radius of the area. In this chart, for this specific machine (bear in mind every load chart will be different for every type of spider crane) the working radius the crane can function at is between 0m – 19m. On the chart you’ll also be able to see which boom length stages will need to be activated as the working radius gets higher.

Hook Height from Ground Level (m)

On the Y-axis of the chart is a variety of measurements in metres for the hook height from ground level that the crane can operate at. For this specific crane the hook height it can work at is between 0m – 19m.

Determining the Load

By looking at the working radius that’s needed with the hook height that’s needed, one can determine what the spider crane lifting capacity can be. Here is a practical example:

Job A:

The working radius for the crane for Job A is 5m. The working height for the load for the crane is 11m. By matching the two points up on the chart, it can be determined that the load capacity of this spider crane (UNIC URW-547) for Job A will be 3 tonnes.

If you have a need for a spider crane in your industrial, mining or construction project, call in the experts at Concord Access Solutions today to help you determine what kind of spider crane you need to get the job done.

Find out more about spider crane specs available for the UNIC spider cranes we have in our fleet now by calling us on 011 393 6437.