Maritime Knowledge Base
Browse questions and answers across marine machinery, merchant navy careers, shipboard operations and maritime glossary terms.
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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 "Tanker"
What is an inert gas system on a tanker and why is it needed?
An inert gas system fills a tanker's cargo tanks with oxygen-poor gas so the atmosphere cannot support combustion, preventing explosions in and around the cargo.
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.
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.
Maritime GlossaryWhat does STCW mean?
STCW explained — the international convention that sets minimum training, certification and watchkeeping standards for seafarers worldwide.
Maritime GlossaryWhat is deadweight tonnage (DWT)?
Deadweight tonnage defined — the total weight a ship can carry — and how it differs from displacement and gross tonnage.
Merchant Navy CareersHow much do merchant navy officers earn?
What drives merchant-navy pay — rank, ship type, company and trade — and why officer salaries are usually quoted per month at sea.
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.
Merchant Navy CareersHow do you become a ship captain (Master) in the merchant navy?
Becoming a ship's captain means progressing through the deck department from cadet to Master, building sea time and passing successive Certificates of Competency.
Shipboard OperationsWhat is a Shipboard Oil Pollution Emergency Plan (SOPEP)?
SOPEP is the Shipboard Oil Pollution Emergency Plan, a MARPOL-required plan that tells the crew how to report and respond to an oil spill from the ship.
Merchant Navy CareersWhat are the four STCW basic safety training courses?
Before joining a ship, every seafarer must complete STCW basic safety training — four short courses covering survival, firefighting, first aid and personal safety.
Shipboard OperationsWhat is a hot work permit and when is it needed?
A hot work permit controls any work involving heat, flame or sparks outside a designated safe area, confirming the space is gas-free and fire precautions are in place.
Marine MachineryHow does a marine diesel engine work?
A marine diesel engine converts the chemical energy of fuel into rotary motion through compression ignition — here is the working principle and the two-stroke and four-stroke cycles.
Marine MachineryWhat is the difference between a two-stroke and a four-stroke marine engine?
Two-stroke and four-stroke marine engines differ in how many strokes complete a cycle, their speed and size, and the roles they play aboard ship.
Marine MachineryHow does a marine boiler work?
A marine boiler generates steam by transferring heat to water — this covers the working principle and the difference between oil-fired and exhaust-gas boilers.
Merchant Navy CareersCan women join the merchant navy and what roles can they hold?
Yes — women can and do serve in every department and rank of the merchant navy, from cadet to Master and chief engineer, and the industry is actively working to recruit more.
Merchant Navy CareersWhat shore-based jobs can experienced seafarers move into?
Experienced seafarers are in demand ashore for a wide range of maritime roles — surveying, pilotage, ship management, training, insurance and port work — where their sea experience is essential.
Merchant Navy CareersWhat is the difference between the merchant navy and the (military) navy?
The merchant navy is the commercial fleet that carries cargo and passengers for trade, crewed by civilian seafarers, while the navy is a country's military maritime force.
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 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.
Marine MachineryWhat is a reduction gearbox on a ship and why is it used?
A reduction gearbox lowers the high rotational speed of a medium- or high-speed engine to the slower speed that turns an efficient propeller, and can combine several engines onto one shaft.
