BD Marine Engineer Class 4 (Coastal CE) key terms

The average pressure that would act on the piston through one complete cycle to produce the measured shaft output, calculated from torque and engine geometry. It allows comparison of the work output of engines of different sizes.

The average pressure derived from the indicator diagram of the cylinder, representing the work done on the piston per cycle. It is always greater than brake mean effective pressure because friction losses are included.

The ratio of brake power delivered at the shaft to indicated power developed inside the cylinders, expressed as a percentage. It quantifies the share of cylinder work lost to friction in bearings, pistons and driven pumps.

A pressure-volume or pressure-crank angle plot recorded from a cylinder during operation. Engineers use it to assess combustion quality, valve timing, peak pressure and power balance between units.

The maximum cylinder pressure reached just after top dead centre during combustion. Excessive values stress components and indicate over-advanced injection or overload, while low values suggest poor atomisation or leakage.

The crank angle at which fuel delivery into the cylinder begins, usually expressed in degrees before top dead centre. Correct timing governs ignition delay, peak pressure and thermal efficiency.

The interval between the start of fuel injection and the onset of measurable combustion pressure rise. Long delays cause rapid pressure rise, knocking and high peak pressures in diesel engines.

An unstable condition in which compressor airflow reverses cyclically, producing loud pulsations and vibration. It arises from blocked air filters, fouled turbine nozzles, rapid load changes or mismatched turbocharger and engine matching.

Fresh charge air delivered by the turbocharger or blower to the cylinder to remove exhaust gases and supply oxygen for combustion. Its pressure and quantity directly influence combustion and thermal loading.

A heat exchanger that cools compressed charge air before it enters the cylinder, increasing air density and reducing thermal load. Cooling water flow and cleanliness determine its effectiveness.

A measure of the ignition quality of diesel fuel, indicating how readily it self-ignites under compression. Higher values shorten ignition delay and give smoother, quieter combustion.

A violent ignition of oil mist in the crankcase, typically following a local hot spot that vaporises lubricating oil. Prevention relies on oil mist detection, prompt slowdown and controlled crankcase relief doors.

A device that continuously samples crankcase atmosphere and alarms when suspended oil droplets exceed a set density. It provides early warning of overheating bearings or pistons before an explosive concentration forms.

A spring-loaded flap fitted to crankcase doors that opens at low pressure to vent gases outward and prevent structural rupture. It is arranged to discharge away from walkways and hot surfaces.

A rotating bowl separator that removes water and solid contaminants from fuel or lubricating oil by density difference. Correct gravity disc selection and throughput rate determine separation efficiency.

An interchangeable ring fitted in a centrifugal separator bowl that sets the position of the oil-water interface. Choosing the wrong disc causes either water carry-over into the oil or oil loss with the water.

A measure of a fuel's resistance to flow, which governs atomisation quality and pumping behaviour. Heavy fuels are heated to a specified viscosity at the injector, typically measured in centistokes.

Equipment that treats oily bilge water to reduce oil content below the permitted discharge limit before overboard release. It typically combines gravity separation, coalescing filters and an oil content monitor.

An instrument that continuously measures the oil concentration in treated bilge water and automatically stops discharge or alarms when the set limit is exceeded. It is essential for compliant machinery space operation.

A statutory register in which all oil transfers, sludge disposals, bilge discharges and bunkering operations are recorded. Entries must be signed by the responsible officer and are subject to inspection by authorities.

The international regulations governing prevention of pollution by oil, covering discharge limits, equipment requirements and record keeping. It applies to tankers and machinery spaces of all qualifying ships.

An independent generating set kept ready to supply essential services automatically on loss of the main supply. It is tested regularly to confirm starting, voltage and frequency performance.

A distribution board supplied by the emergency generator or battery, feeding safety-critical circuits such as steering gear, alarms and emergency lighting. It is located above the bulkhead deck for flooding protection.

An automatic load-shedding arrangement that disconnects non-essential consumers in stages when generator load becomes excessive. It protects the alternator from overload and preserves power to essential services.

The procedure for restoring a vessel from a completely blacked-out condition using the emergency source and then the main generators. It demonstrates that the electrical system can be recovered without external assistance.

An industrial computer that executes stored logic to control machinery sequences, interlocks and alarms. It replaces relay logic and allows monitoring and fault diagnosis through a connected terminal.

A classification notation permitting the engine room to operate without a permanent watch, relying on automated monitoring, alarms and safety shutdowns. Periodic inspection rounds and call-out systems remain mandatory.

A network of sensors and displays that warns of abnormal temperatures, pressures, levels and running conditions. Alarms are graded, logged and often interlocked to automatic slowdown or shutdown.

The maximum load that lifting gear or an attachment is certified to bear safely under stated conditions. It is marked on the equipment and must never be exceeded during maintenance operations.

A formal written authorisation procedure controlling high-risk tasks such as hot work, isolation and enclosed space entry. It records hazards, precautions, isolations and acceptance signatures before work starts.

Entry into a tank, cofferdam or void where atmosphere may be deficient in oxygen or contain toxic or flammable gas. It requires testing, ventilation, a permit, a standby person and rescue equipment.

Division of the hull into compartments by watertight bulkheads and decks to limit flooding after damage. It preserves buoyancy and stability and is defined by the ship's subdivision load lines.

The foremost watertight transverse bulkhead, positioned a defined minimum distance aft of the stem. It limits flooding in a bow collision and protects the rest of the hull.

The ability of a ship to remain afloat and upright after specified compartments are flooded. It is assessed against survival criteria covering residual freeboard, heel and range of stability.

The apparent rise in centre of gravity caused by liquid shifting in partially filled tanks as the ship heels. It reduces metacentric height and can seriously impair stability.

The vertical distance between the centre of gravity and the metacenter, indicating initial transverse stability. A small positive value gives a tender ship, while an excessive value gives stiff, rapid rolling.

A pressurised pipeline supplying seawater to hydrants, hoses and fixed firefighting systems throughout the ship. It is maintained by the fire pump and must remain available at all times.

A total-flooding extinguishing installation that releases carbon dioxide into a protected space to displace oxygen. Release requires evacuation, space sealing, headcount and strict precautions against asphyxiation.

A permanently displayed drawing showing fire boundaries, appliances, escape routes and control stations. It guides the crew and shore firefighters during an emergency response.