Understanding Crane Load Charts: How Do We Determine Rope Capacity?

Dear all, We have a 200MT crawler crane with a lattice boom at the site. Initially, there was a 4-fall rope in the crane. However, it has now been extended with a 2-fall rope. I have a couple of doubts:

1. Does the load chart mention only the boom capacity?
2. If yes, then how can we determine the rope capacity?

The crane operator mentioned that the load chart value is only for the boom angle and its capacity. The rope being used is 28mm thick, but the exact type is unknown. The operator mentioned a capacity of 14 MT per fall for the rope.

Please provide clarification on these points.

Regards, Vijay

What I suggest to you is to please check the crane owner's manual. It should be addressed in the owner's manual.

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As mentioned by Raghu, carefully check the load chart and the number of falls for the capacity. Sometimes, the foremen opt for a shortcut method of reducing the falls to save time during the lift. Are you referring to the fly jib? The fly jib typically uses a single rope fall with a ball hook for such cranes.

Regards,
Pon

As per your description, there is definitely a chance of a reduction in SWL if the fall is reduced to 2 from 4. However, in this case, you have to check the breaking strength of the rope because during the crane's SWL design, the breaking strength of the rope is considered. Therefore, if you consider the normal SWL of the rope for 28mm, you will not obtain the accurate figure. Additionally, please refer to the crane manual to determine the number of falls recommended by the manufacturer for a 250-ton SWL. This information may provide you with further insight. Such details are not typically available from the load chart; consulting the crane manual is essential to clarify your doubts.

Furthermore, ensure you check the type of rope being used, whether it is a locked coil rope, non-spinning rope, or any other special type. For special ropes used in cranes, the SWL may be significantly higher (potentially double) based on the calculation of 8d². All these specifics can be found in the manual. Without the manual, reaching a safe conclusion may pose challenges. It is crucial not to assume that nothing will happen, as per the operator's experience.

Regards,
ASHOK KUMAR

Mr. Pon and Mr. Ashok have provided an answer to your query. Please let us know if you need further assistance.

Thanks for your inputs, Mr. Pon and Mr. Ashok. Keep on sharing.

Thank you for your valuable suggestions. I do not have a manual for the particular crane; only the load chart is available. The number of falls in the crane is not mentioned in that chart. I have identified the type of rope and calculated the Safe Working Load (SWL). The SWL is indicated in the load chart in conjunction with the boom angle and work radius. My question is whether the SWL provided is solely for the boom capacity or if it includes the hoisting rope. Due to the lack of a crane manual, I have been unable to find the answer.

Regards, Vijay

Dear Vijay,

The SWL mentioned in the Load Chart always considers the hoisting rope as well. There is no need to get any further confused.

Concept of Capacity Lifting

Did you know about the concept of Capacity Lifting? First of all, we should not encourage the use of cranes without an SLI installed. If there is no SLI, you should only allow lifting up to 50% of the Capacity Lifting. This means if the Load Chart shows a lifting capacity of 10 tons, you may suggest lifting up to 5 tons.

Regards,

Hi,

How do you calculate the Wire Rope Safe Working Load (SWL)? Is 8d square involved in the calculation? Are you referring to a 1-inch Wire Left-hand Lang's Lay Rope with a Grade of 1960 N/mm?

Please provide more context so I can assist you accurately. Thank you.