Maritime Knowledge Base
Browse questions and answers across marine machinery, merchant navy careers, shipboard operations and maritime glossary terms.
Browse by Category
Marine Machinery
Troubleshooting guides for pumps, boilers, purifiers, compressors and auxiliary systems.
Merchant Navy Careers
Questions about joining the merchant navy, exams, cadetships, ranks and sea-time.
Maritime Glossary
Plain-English definitions of shipping, engine-room, navigation and regulatory terms.
Shipboard Operations
Practical Q&A for watchkeeping, safety, maintenance routines and onboard documentation.
Results for "Seawater"
How does a marine fresh water generator (evaporator) work?
A fresh water generator makes drinking and technical water from seawater by boiling it under vacuum using waste heat from the engine, then condensing the vapour.
Marine MachineryWhat is a central cooling system on a ship and why is it used?
A central cooling system uses seawater to cool a closed freshwater circuit, which in turn cools the machinery — reducing seawater corrosion and fouling in the equipment.
Marine MachineryWhat is the stern tube and stern tube seal on a ship?
The stern tube is the tube through which the propeller shaft passes out of the hull; it carries the aft bearing and a seal that keeps seawater out and lubricant in.
Maritime GlossaryWhat is ballast water and why is it managed?
What ballast water is, why ships carry it, and why it is now exchanged or treated under the Ballast Water Management Convention.
Marine MachineryWhy is my main engine jacket cooling water temperature high?
Working through high jacket-water temperature — flow, the cooler, the sea and central-cooling side, thermostats, air locks and load.
Marine MachineryHow does a ship's refrigeration plant work?
A marine refrigeration plant uses the vapour-compression cycle to move heat out of provision rooms or cargo spaces, keeping food and cargo cold at sea.
Shipboard OperationsWhat is crude oil washing (COW) on a tanker?
Crude oil washing cleans a tanker's cargo tanks during discharge by spraying them with the crude cargo itself, which dissolves clingage and reduces residue, sludge and pollution.
Marine MachineryHow does a ship's sewage treatment plant work?
A marine sewage treatment plant breaks down the ship's sewage — usually biologically — and disinfects it so that the treated effluent meets MARPOL Annex IV discharge standards.
Shipboard OperationsHow is a cargo tank cleaned on a tanker?
Cargo tanks are cleaned with fixed or portable washing machines using water or crude oil, followed by draining, gas-freeing and ventilation, before a change of cargo, entry or repair.
Shipboard OperationsHow is ballast water managed and treated on board a ship?
Under the Ballast Water Management Convention, ships manage ballast water either by mid-ocean exchange or, increasingly, by treating it through an approved system before discharge.
Marine MachineryWhat is jacket cooling water in a marine engine?
Jacket cooling water is the treated fresh water circulated through the passages, or jackets, around an engine's cylinders to carry away combustion heat and keep it at its correct working temperature.
Marine MachineryHow does a marine centrifugal pump work?
A centrifugal pump moves liquid by spinning it with an impeller, which throws the liquid outward and converts its speed into pressure — the most common type of pump aboard ship.
Marine MachineryHow does a marine heat exchanger work?
A heat exchanger transfers heat from one fluid to another through a dividing wall without letting them mix — used all over a ship to cool engines, oil and air.
Marine MachineryWhat is the difference between a controllable-pitch and a fixed-pitch propeller?
A fixed-pitch propeller has blades set at one permanent angle, while a controllable-pitch propeller can rotate its blades to vary thrust and go astern without reversing the engine.
Shipboard OperationsWhat is under keel clearance and why is it important?
Under keel clearance is the vertical gap between the lowest point of a ship's keel and the seabed — a safety margin that must be maintained to avoid grounding.
