Propulsion & Steering Systems

Steering gear

Machinery that moves the rudder in response to steering commands. SOLAS requires main and auxiliary steering arrangements, or an accepted equivalent configuration with multiple identical power units, together with prescribed controls from the bridge and steering-gear compartment.

Main engine

The ship's principal engine — on most cargo ships a huge low-speed diesel driving the propeller directly. Its type and fuel choice cascade through the whole ship design.

Propeller (FPP / CPP)

The propeller converting engine power to thrust. A fixed-pitch propeller (FPP) is a solid casting; a controllable-pitch propeller (CPP) can twist its blades to change thrust without changing engine speed.

Shafting & bearings

The steel shaft line and its support bearings that carry engine power from inside the hull out to the propeller.

Stern tube & sealing

The tube where the shaft passes through the hull, with seals that keep the sea out and the lubricating oil in at that critical penetration.

Turning gear

A small geared motor that rotates the main engine very slowly during maintenance, positioning the crankshaft safely for work and preventing a stopped hot engine from sagging.

Torsional / axial vibration damper

Devices on the shaft line that absorb the twisting and lengthwise vibrations a large diesel naturally produces, protecting the crankshaft and shafting from fatigue.

Main engine remote control

The system that transmits bridge and control-room commands — ahead, astern, speed — to the engine, with the interlocks that stop unsafe orders being executed.

Main engine safety system

An independent protective layer that automatically slows or stops the main engine when critical limits are breached, such as loss of lubricating oil pressure or overspeed.

Electronic engine control (ECU)

The computer that governs a modern electronically controlled engine, timing fuel injection and valves precisely; on dual-fuel engines it also manages the switch between gas and oil.

Azimuth / POD propulsion

Propulsion units that rotate 360 degrees, combining propeller and rudder in one steerable pod — standard where fine manoeuvring is the mission, as on offshore vessels.

Bow / stern tunnel thrusters

Propellers mounted sideways in tunnels through the hull ends that push the bow or stern sideways, letting the ship berth with less or no tug assistance.

Reduction gearbox and clutch system

Gearing that converts a medium-speed engine's fast rotation to efficient slow propeller speed, with clutches to connect and disconnect engines — the standard arrangement on ferries and many working ships.

CPP hydraulic power and pitch-control system

The hydraulic pumps, oil distribution box and controls that twist the blades of a controllable-pitch propeller to the commanded angle.

Electric propulsion motor system

Large electric motors that turn the propellers on diesel-electric ships, decoupling engines from the shaft so generators can run at their best point and be placed flexibly.

Propulsion converters and propulsion transformers

The power-electronics converters and transformers that condition electrical power for the propulsion motors, controlling their speed smoothly from zero to full.

Waterjet propulsion system

Propulsion that pumps water through steerable nozzles instead of using propellers — the usual choice on high-speed craft, giving shallow draught and agile steering.

Wind-assisted propulsion system (WAPS)

Modern sails — rotors, rigid wings or suction sails — that use wind to reduce engine power demand, with controls that trim them automatically to the conditions.

Air-lubrication system

Compressors and hull outlets that blow a carpet of small bubbles under the flat bottom, reducing friction between hull and water and saving several percent of fuel.

Oil tankers

Chemical tankers

LNG carriers

LPG, ethylene, ethane, ammonia, CO2, hydrogen and gas-bunkering carriers

Bulk carriers and specialised dry-bulk carriers

General and specialised break-bulk cargo ships

Multipurpose, open-hatch, deck, heavy-lift and heavy-transport ships

Container ships

Ro-ro cargo and vehicle carriers

Refrigerated cargo ships

Fishing vessels, factory trawlers and live-fish carriers

Cruise and passenger ships

Ro-ro passenger ferries

PSV, AHTS, OSV/SOV and CTV

Cable, pipe, diving, subsea construction, WTIV and intervention vessels

Drillship, FPSO, FSO, FSU, FLNG and FSRU

Dredgers and hopper dredgers

Tugs, ERRV/standby, pilot and search-and-rescue craft

Research, hydrographic, seismic and icebreaking vessels

Large yachts and superyachts

Patrol and government service vessels