A derrick is a cargo-handling boom, hinged at its base and supported by wire rigging, used to lift and swing cargo between the ship’s hold and the quay (or another vessel) — one of the older forms of ship’s cargo gear.
How a Derrick Works
A derrick boom pivots at its base (typically at a mast or post), with its outer end supported and controlled by a system of topping lifts (wires controlling the boom’s angle) and cargo runners (the lifting wire itself, running through blocks). By adjusting the topping lift and swinging the boom, cargo can be lifted from the hold and swung out over the ship’s side to the quay.
Derrick vs Crane
- Derrick — a simpler system using wire rigging and manual/winch control of boom angle and swing; requires more rigging setup and skilled operation
- Crane — a self-contained, typically hydraulically or electrically powered unit with integrated slewing (rotation) and luffing (angle adjustment) — faster, more precise, and requiring less setup
Modern vessels have largely replaced derricks with cranes, given the significant efficiency advantage — but derricks aren’t entirely obsolete.
Where Derricks Are Still Found
Some general cargo vessels, particularly older ships or those trading to ports without adequate shore-based cargo-handling infrastructure, still carry derrick rigs — valued specifically because they don’t depend on the vessel’s own crane systems being operational, or on the port having adequate shore cranes.
Union Purchase Rig
A traditional derrick configuration — “union purchase” — uses two derricks rigged together, one over the hold and one over the quay, working in combination to lift cargo from the hold and swing it directly to the quay without needing a single derrick to reach the full distance alone. This is a genuinely skilled cargo-handling technique, less commonly seen as cranes have become standard.
Safety Considerations
Derrick rigging — wire condition, block and tackle inspection, safe working load compliance — is subject to the same rigorous inspection and certification requirements as any other lifting equipment aboard ship, given the real injury risk from rigging failure during cargo operations.
Exam Relevance
Derrick operation, the union purchase rig, and derrick-vs-crane distinctions are covered within Cargo Work and Ship Knowledge topics in deck officer competency exams.