MARINA Second Engineer / Chief Engineer Theoretical Exam cheat sheet

Thermal efficiency of an ideal Diesel cycle = 1 − (1/r^(γ−1)) · (ρ^γ − 1)/(γ(ρ − 1)), where r = compression ratio, ρ = cut-off ratio, γ = cp/cv.

Indicated power (single-acting four-stroke, one cylinder) = pmi · L · A · N / (2 · 60) in kW, with pmi in kPa, L and bore in m, N in rpm.

Brake specific fuel consumption (bsfc) = fuel mass flow (kg/h) ÷ brake power (kW); typical large two-stroke values are 160–175 g/kWh.

Volumetric efficiency = actual air mass delivered per cycle ÷ theoretical swept-volume air mass at intake conditions; scavenge air excess ratio λ is typically 2.0–2.5 for two-strokes.

Heat balance rule: fuel energy = brake work + jacket cooling + exhaust + radiation/lubricating-oil losses; exhaust and cooling together commonly account for 40–50%.

Compression ratio r relates to swept volume Vs and clearance volume Vc by r = (Vs + Vc)/Vc; raising r raises thermal efficiency but raises peak firing pressure.

Mean effective pressure pme = 2π · nR · T / Vs for a four-stroke (per cycle work divided by swept volume); pme is the load indicator independent of engine size.

For torsional vibration, resonance occurs when a harmonic excitation order equals the shaft natural frequency; barred-speed ranges must be avoided in the operating band.

Propeller law: absorbed power P ∝ N³ and thrust/drag ∝ N² for a fixed-pitch propeller, so a 10% rpm increase raises power demand by about 33%.

Diesel engine governor droop (speed droop) = (N_no-load − N_full-load)/N_rated × 100%; 3–5% is typical for propulsion engines, zero droop for alternators in isochronous mode.

Two-stroke crosshead engines use a separate cylinder oil feed (often 0.6–1.2 g/kWh, adjusted by sulphur content) and a system oil for bearings; four-strokes use a common sump oil.

Starting air: minimum 12 starts for reversible engines and 6 for non-reversible, per SOLAS II-1; air bottles normally at 30 bar (25–30 bar working range).

Turbocharger surging is indicated by repeated pressure pulsations and is countered by reducing load, cleaning the air side, or checking nozzle ring and charge-air cooler fouling.

Cylinder liner wear rate target is generally below 0.05 mm per 1,000 hours; excessive wear points to incorrect cylinder oil feed, fuel sulphur, or poor combustion.

Slow-steaming reduces fuel consumption roughly with N³ but increases fouling, low-load turbocharger efficiency loss, and risk of poor combustion; minimum stable load must be respected.

Crankcase explosion prevention: oil mist detector alarm at 2.5% LEL (0.05 mg/l range) triggers immediate load reduction and investigation; never open crankcase doors before cooling.

Pump affinity laws: Q ∝ N, H ∝ N², P ∝ N³ for a centrifugal pump at constant impeller diameter; throttling moves the operating point along the system curve.

Centrifugal pumps must be primed and started with the discharge valve closed (or partly open); never run dry - cavitation occurs when NPSH available falls below NPSH required.

NPSH_a = (p_atm − p_vapour)/(ρg) + static head − friction losses; a rising suction temperature lowers NPSH_a because vapour pressure rises.

Purifier bowl separation depends on the Stokes-law settling velocity; throughput must be reduced when viscosity rises or density difference between oil and water falls.

Boiler safety valves: at least two, set to lift not later than design pressure; the boiler must not be fired with low water level - low-water interlock cuts fuel.

Air compressor intercooler and aftercooler reduce compression work and condensate; drain traps must be checked to prevent water carry-over into air receivers.

Freshwater generator uses jacket-water heat; output falls as vacuum is lost or scale builds on the evaporator tubes; scale is removed by acid cleaning per maker's procedure.

Steering gear: SOLAS requires two independent power actuating systems or one system with two independent pump units; main and auxiliary steering gear drills are held every 3 months.

Three-phase power P = √3 · V_L · I_L · cos φ; a low power factor increases current for the same kW and raises generator and cable loading.

Synchronous generator parallel operation requires matching voltage, frequency, phase sequence, and phase angle; load sharing is set by governor speed droop.

Insulation resistance testing: minimum acceptable values per IEC 60092 are typically ≥1 MΩ at 500 V DC for low-voltage circuits; record and trend readings.

Short-circuit protection: discrimination requires the downstream breaker to trip before the upstream device; check time-current curves rather than ratings alone.

Earthing systems: an IT (isolated) distribution is standard on ships, so a single earth fault does not trip; an earth-fault alarm must be found and cleared promptly.

PID control: proportional band, integral time, and derivative time; integral action removes offset, derivative reduces overshoot but amplifies measurement noise.

Battery and UPS: lead-acid cells give 2.0 V nominal, vented; charging voltage is temperature-compensated; hydrogen must be ventilated from battery rooms.

Automatic voltage regulator maintains generator terminal voltage within ±2.5% steady state; excitation loss causes reactive power import and possible pole slipping.

STCW rest hours: minimum 10 hours rest in any 24-hour period and 77 hours in any 7-day period; rest may be split into no more than two periods, one at least 6 hours.

Watch handover must include: machinery status, ongoing work and permits, abnormal readings, fuel/water/lube levels, and standing orders; never hand over during a critical manoeuvre.

Unattended machinery space (UMS) requires alarms and safety systems tested before the ship enters UMS mode; the engineer on call must be within the alarm response time.

Manoeuvring: acknowledge bridge order, repeat it, execute, and report; standby time before manoeuvring is typically 1 hour, with steering gear tested and air bottles full.

Engine room log readings are taken at fixed intervals (normally hourly at sea) and compared with trends; deviations from baseline trigger investigation, not just recording.

Bunkering checklist: agreed transfer rate, tank soundings before/after, scuppers plugged, overflow tank monitored, communication with barge, and drip trays in place.

Blackout recovery: emergency generator auto-starts within 45 s per SOLAS; main engine restart requires starting air and fuel supply; the sequence is drilled regularly.

Permit-to-work systems cover hot work, enclosed-space entry, working aloft, and electrical isolation; the isolation certificate must be signed by the responsible engineer.

Planned maintenance system (PMS) schedules by running hours, calendar time, or condition; condition-based tasks use vibration, oil analysis, thermography, and performance trending.

Wear limits must come from the maker's manual; for example, cylinder liner wear and piston-ring groove clearance have stated maximum values, and exceeding them requires renewal.

Vibration monitoring: overall velocity (mm/s RMS) per ISO 10816 bands; a rising trend or step change indicates misalignment, unbalance, bearing wear, or looseness.

Oil analysis: check viscosity, water content, total base number (TBN), insolubles, and wear metals (Fe, Cu, Pb, Sn, Si); trend over time rather than one-off values.

Spare parts management: critical spares identified by failure consequence; minimum stock levels set from lead time and consumption rate, with certificates retained.

Overhaul records should capture measured clearances before and after, parts replaced, torque values, and running hours, so the next interval can be adjusted.

Class surveys: annual, intermediate, and special (5-year) surveys; continuous survey machinery (CSM) spreads items across the cycle and requires a planned schedule.

Defect reporting: machinery defects affecting class or safety are reported to class and flag state; temporary repairs need approval and are time-limited.

MARPOL Annex I: oily water separator discharge must be ≤15 ppm with an approved alarm and automatic stopping device; discharge is prohibited in special areas.

MARPOL Annex VI sulphur limits: 0.50% m/m global and 0.10% m/m in ECAs; compliance by low-sulphur fuel, scrubber, or alternative fuel, with records and changeover logs.

NOx Tier limits apply to engines over 130 kW; Tier III applies in NOx ECAs for new engines and requires SCR or equivalent; Tier I/II apply outside.

Oil record book entries must be made without delay for each transfer, disposal, or OWS operation; falsification is a criminal offence in most jurisdictions.

Garbage management per MARPOL Annex V: food waste discharge limits depend on distance from land and comminution; plastics may never be discharged.

Ballast water management: D-1 exchange or D-2 treatment per the BWM Convention; records and a ballast water record book are mandatory.

SOPEP and emergency drills: oil spill response equipment must be inventoried and drills logged; reportable spills go to the coastal state without delay.

Energy efficiency: EEXI and CII apply to ships over 5,000 GT; SEEMP Part II and III are required, and CII rating (A–E) affects chartering.

SOLAS Chapter II-1 covers subdivision and machinery; Chapter II-2 fire safety; Chapter IX ISM; Chapter XI-1/2 surveys and port state control.

STCW certification: officer of the watch requires sea service, approved training, and competence assessment; certificates of competency are issued by the flag state.

MARPOL certificates (IOPP, ISPP, IAPP, IEEC) are issued after survey and must be on board and valid; expiry stops trading.

ISM Code requires a Safety Management System with a designated person ashore, master's authority, and documented procedures; non-conformities are recorded and closed out.

MLC 2006 covers crew accommodation, hours of rest, wages, repatriation, and complaint procedures; it is enforced by flag and port state.

Port state control: deficiencies can lead to detention; the ship must rectify before departure, and detentions are published in regional databases.

UNCLOS and collision regulations: COLREGS Rule 2 (good seamanship) and Rule 5 (lookout) apply to all vessels; engineers must understand manoeuvring signals.

Flag state vs port state: flag state exercises jurisdiction over the ship; port state verifies compliance when in port under its jurisdiction.

Archimedes: displacement (tonnes) = underwater volume (m³) × density (t/m³); for seawater use 1.025 t/m³.

GM = KM − KG; positive GM gives initial stability; GZ curve area gives dynamical stability; IMO intact stability criteria include area under GZ to 30° ≥ 0.055 m·rad.

Free surface effect reduces effective GM by FSC = i·ρ / (Δ) summed over tanks; longitudinal subdivision reduces free surface moment.

Damage control: flooding a compartment raises KG and may create free surface; counter-flooding must consider list and longitudinal strength.

Watertight subdivision: collision bulkhead position per SOLAS, double bottom height, and watertight doors must be operable and tested; indicator lights on the bridge.

Hull stress: still-water bending moment plus wave-induced bending; engineers must avoid uneven ballast/fuel distribution that raises hogging or sagging stress.

Fire triangle and fire classes: A (solid), B (liquid), C (gas), D (metal), F (cooking oil); fixed systems include CO2, foam, water mist, and dry powder.

Enclosed space entry: test oxygen (20.9%), hydrocarbons, CO, and H2S before entry; continuous monitoring and a standby person at the entrance are required.

Archimedes: displacement (tonnes) = underwater volume (m³) × density (t/m³); for seawater use 1.025 t/m³.

GM = KM − KG; positive GM gives initial stability; GZ curve area gives dynamical stability; IMO intact stability criteria include area under GZ to 30° ≥ 0.055 m·rad.

Free surface effect reduces effective GM by FSC = i·ρ / Δ summed over tanks; longitudinal subdivision reduces free surface moment.

Damage control: flooding a compartment raises KG and may create free surface; counter-flooding must consider list and longitudinal strength.

Watertight subdivision: collision bulkhead position per SOLAS, double bottom height, and watertight doors must be operable and tested; indicator lights on the bridge.

Hull stress: still-water bending moment plus wave-induced bending; engineers must avoid uneven ballast/fuel distribution that raises hogging or sagging stress.

Fire triangle and fire classes: A (solid), B (liquid), C (gas), D (metal), F (cooking oil); fixed systems include CO2, foam, water mist, and dry powder.

Enclosed space entry: test oxygen (20.9%), hydrocarbons, CO, and H2S before entry; continuous monitoring and a standby person at the entrance are required.