NATARAJAHeavy lifts & the ship's gear
Learning outcomes & permitted supports
- Place the weight where it truly acts the instant it lifts — at the derrick head
- Find the rise of G, the GM during the lift, and the list at any outreach
- Solve the planning question: the heaviest lift that keeps GM above the company floor
- Quote the proof-load table across its three bands and the testing regime around it
- Prepare the ship: tanks pressed or empty, GM computed BEFORE the wire takes weight
Supports in this lab: Calculator. Transfer-of-G physics verified against the moment-table chain in golden (840/840); proof-load table as taught for the paper — ship's register and class rules govern the real gear.
The moment it leaves the quay
A wire can pull only along itself — so the instant the parcel lifts, its weight acts at the derrick head, 24 m up, not at the hook or the deck. G jumps the moment the load comes on; nothing more happens as the weight is hoisted higher.
| W (ship + weight) · KM | 13311.7 t · 7.40 m |
|---|---|
| GM before the lift | 1.204 m |
| Rise of G at lift-off | 0.198 m — w × (head − cg on quay) / W |
| GM during the lift | 1.006 m |
| List with the boom at 10 m outreach | 0° (still on the quay) |
The gear itself — SWL and the proof load
Every derrick, crane, block and shackle carries a Safe Working Load. At test, the gear must hold MORE — the proof load of the classical testing table. (Ship's register and class rules govern the real gear; this is the table the paper wants.)
| SWL | proof load rule | proof load |
|---|---|---|
| 10 t | 1.25 × SWL | 12.5 t |
| 20 t | 1.25 × SWL | 25.0 t |
| 30 t | SWL + 5 t | 35.0 t |
| 50 t | SWL + 5 t | 55.0 t |
| 80 t | 1.10 × SWL | 88.0 t |
The regime around the numbers: initial test before first use, retest every five years, annual thorough examination by a competent person, quadrennial… all entered in the ship's Register of Lifting Appliances — the document a port state inspector opens first.