BTEB Diploma in Marine Engineering Examination key terms

The average pressure that, if applied to the piston throughout its power stroke, would produce the measured brake power of an engine. It allows comparison of power output between engines of different sizes.

The average pressure acting on the piston during a complete working cycle, calculated from the indicator diagram. It represents the gross work delivered to the piston before friction and auxiliary losses are deducted.

A pressure-versus-crank-angle or pressure-versus-volume plot taken from a cylinder, used to assess combustion quality, peak firing pressure, and power developed. Modern engines record it electronically for analysis and fault diagnosis.

The mass of fuel consumed per unit of brake power per hour, usually expressed in grams per kilowatt-hour. It is a key efficiency indicator for comparing engine performance and monitoring deterioration.

A machine in which exhaust gas drives a turbine connected to a compressor that raises the pressure of combustion air entering the engine. It increases the mass of air trapped in the cylinder, allowing more fuel to be burned.

The process of flushing burnt gases out of the cylinder and filling it with fresh air before compression begins. Efficiency of scavenging strongly affects combustion quality and power output in two-stroke engines.

A heat exchanger that cools compressed charge air after the turbocharger, increasing its density before it enters the cylinder. Cooling also limits thermal loading and improves combustion efficiency.

The maximum cylinder pressure reached during combustion, measured relative to top dead centre. Excessive values indicate overloading or faulty injection timing and can cause mechanical damage.

The crank angle at which fuel injection begins relative to top dead centre. Correct timing balances power, fuel economy, and emissions; late or early injection changes peak pressure and exhaust temperature.

A rapid combustion of oil mist inside the crankcase, usually ignited by a hot spot such as a seized bearing. It is prevented by oil mist detection, reliable breathers, and prompt investigation of abnormal temperatures.

A device that continuously samples crankcase atmosphere and raises an alarm when suspended oil droplets exceed a safe concentration. It gives early warning of overheating components before an explosive concentration develops.

Continuous measurement of main bearing, crankpin bearing, and thrust bearing temperatures to detect inadequate lubrication or excessive loading. Rising trends trigger inspection before damage or crankcase ignition occurs.

A rotodynamic machine that imparts kinetic energy to liquid through a rotating impeller, converting it to pressure in the casing. It suits large flows at moderate heads and requires priming before starting.

The margin of absolute pressure above the liquid's vapour pressure available at the pump suction. Insufficient NPSH causes cavitation, noise, and erosion of the impeller.

Formation and collapse of vapour bubbles in a liquid where local pressure falls below vapour pressure. In pumps and propellers it produces noise, vibration, and progressive surface erosion.

The operation of filling a pump and its suction line with liquid so that no air pocket remains. A centrifugal pump that is not primed loses suction and cannot develop discharge pressure.

A high-speed rotating bowl that separates water and solid impurities from fuel or lubricating oil by density difference. Correct temperature and throughput are essential for effective separation.

A storage tank in which fuel is held so that heavy solids and free water settle by gravity before the fuel is transferred to service tanks. It provides the first stage of fuel treatment.

Maintaining fuel oil at the viscosity specified for injection by heating or cooling. Incorrect viscosity impairs atomisation, combustion, and pump performance.

The apparent loss of transverse stability caused by liquid shifting freely in a partly filled tank as the ship heels. It raises the virtual centre of gravity and reduces the righting lever.

The vertical distance between the ship's centre of gravity and its transverse metacentre. A small positive value indicates stiff or tender behaviour and is the primary measure of initial stability.

The horizontal distance between the centre of gravity and the line of buoyancy force when a vessel is heeled. Multiplying it by displacement gives the righting moment at that angle.

The ratio of the underwater volume of a hull to the volume of a rectangular block of the same length, breadth, and draught. It indicates how full or fine the hull form is.

The mass of water displaced by a floating vessel, equal to the mass of the ship and everything aboard. It is expressed in tonnes and changes with draught and water density.

The total mass a ship can carry at a given draught, comprising cargo, fuel, fresh water, ballast, stores, and crew. It is the difference between loaded and light displacement.

A technique that prevents corrosion of steel by making it the cathode of an electrochemical cell, using sacrificial anodes or an impressed current. It is widely applied to hulls, tanks, and seawater systems.

A block of a more reactive metal, such as zinc or aluminium alloy, bolted to a structure so that it corrodes preferentially and protects the steel. Anodes are inspected and renewed periodically.

Accelerated corrosion that occurs when two dissimilar metals are in electrical contact in an electrolyte, forming a cell. The less noble metal becomes anodic and deteriorates faster than it would alone.

The part of the international convention dealing with prevention of pollution by oil, covering discharge limits, oil record books, and oily water separator requirements. Compliance is verified through surveys and port state control inspections.

Equipment that reduces the oil content of machinery space bilge water to the permitted limit before discharge overboard. It typically combines gravity separation with a coalescing or filtration stage and an oil content monitor.

A mandatory register in which all oil transfers, discharges, and disposal operations are recorded with date, position, and quantity. Entries must be signed and are subject to inspection by authorities.

Measures taken to prevent the transfer of harmful aquatic organisms between ports through ballast water, including exchange, treatment, and record keeping. An approved management plan and a ballast water record book are required.

Entry into a compartment such as a tank or hold where the atmosphere may be deficient in oxygen or contain toxic or flammable gas. It requires a permit, atmosphere testing, ventilation, and a standby person.

The process of ventilating a tank or compartment until flammable, toxic, or inert gas concentrations and oxygen levels are within safe limits. Results are verified by calibrated instruments before entry is permitted.

A formal written authorisation that defines the task, hazards, precautions, and validity period before high-risk work starts. It ensures that isolation, testing, and supervision are completed and recorded.

The procedure of physically disconnecting and securing energy sources, then applying locks and tags, so that equipment cannot be started during maintenance. It protects personnel from unexpected energisation or release of stored energy.

A measurement of the resistance between an insulated conductor and earth using a high-voltage tester, expressed in megohms. Low values indicate moisture, contamination, or damaged insulation and warn of impending failure.

A portable instrument that applies a high direct voltage to measure insulation resistance of cables, motors, and switchgear. Readings are compared with previous results and manufacturer limits to judge condition.

Deliberate connection of exposed metalwork and neutral points to the ship's hull or an earth electrode. It provides a low-impedance path for fault current and limits touch voltage for personnel.