Understanding Safety Factors: Can My Crane and Lifting Gear Handle These Loads Safely?

Dear Sir,

I would like to clarify the Safety Factor for Mobile Crane / Lifting Gear.

For the Mobile Crane, if we have a mobile crane's SWL of 48,500 Kg at a boom length of 11.5m and a 6m load radius, what is the maximum tonnage that we can carry?

Regarding the Lifting Gear, my material is 12 tons. I have 2 lifting points. Can I use 2 nos. of 6-ton wire ropes for this material?

What are the safety factors for the crane and lifting gears?

I hope you can advise on this.

Thank you.

Answer to the First Part

If the SWL is 48,500 kg at a specific boom length and radius, you can lift the same load—only lift and nothing else. Even this requires a second thought. This load cannot be moved forward/backward or rotated. A crane lift nearing the capacity of the crane at a particular configuration has many factors to consider.

The main factors which affect the lifting of a load are:

• The weight of the load, which includes the weight of the load block, slings, and handling devices.
• The shape of the load.
• The height to which the load is to be raised.
• The final position when raised, and so on.

Determine the boom capacity limitations. These include the length of the boom and the capacity at different radii. To lift the load higher, the boom angle must be lowered. The crane now has decreased capacity, and the stresses imposed on the crane components are increased.

Finally, the LMI or load chart of the crane helps to make a safe lift. Always use it.

Remember, crane operation is a skilled job—leave it to trained personnel.

Answer to the Second Part

If you are using a lifting beam (spreader bar) and only a vertical hitch, yes. If not, no.

There is something called a hitch in crane rigging. It is the arrangement of slings. There are various types of hitches like vertical, choker, and basket.

The capacity of the sling shown on the tag or punched on the hook is for a vertical hitch only. That is, if this sling is attached to the load vertically, it has full capacity. If it is connected at an angle (choker), the capacity is drastically reduced.

Regards,
Kesava Pillai