🔍 Key Concepts
• How safe working load (SWL) is rated for a single pedestal crane versus a twin‑lift arrangement
• What changes (or doesn’t change) when two 30‑ton cranes at one end are then married to another twin pair at the opposite end of the hatch
• How the load is shared between cranes and why it is limited by the weakest part of the system (crane, wire, or gear)
💭 Think About
• First, decide what the maximum safe load is that the two cranes in the illustration can lift together as a twin at one end of the hatch. Is it equal to one crane’s SWL, the sum of both, or something else?
• Next, when that twin is connected to an identical twin at the far end of the hatch, does the total allowable load become: (a) the same as one twin’s rating, or (b) the sum of both twins, or (c) something reduced because of the rigging geometry? Why?
• Think about how many falls/hoists actually carry the weight in the shown configuration and how much of the total load each crane would see if the weight were distributed evenly.
✅ Before You Answer
• Be sure you are using the SWL of the twin‑lift arrangement, not just 30 tons per individual crane, before you start adding anything up.
• Confirm whether the load on each crane in the four‑crane setup would still be within its 30‑ton rating for your chosen answer.
• Check that your choice does not exceed what any single structural component (one crane, one pair, or the connecting gear) could safely carry.