BD Marine Engineer Class 4 (Coastal CE) cheat sheet

Indicated power (kW) = (p_m × L × A × n × k) / 60, where p_m is mean indicated pressure (kN/m²), L stroke (m), A piston area (m²), n revolutions per second, k number of cylinders per cycle factor (1 for two-stroke, 0.5 for four-stroke).

Brake power = indicated power − friction power; mechanical efficiency = brake power / indicated power, typically 0.80–0.92 for medium-speed four-stroke diesels.

Specific fuel consumption (g/kWh) = fuel mass flow (g/h) ÷ brake power (kW); SFOC rises sharply below about 50% load in constant-speed engines.

Two-stroke crosshead engines use piston rods and a stuffing box to keep crankcase oil separate from cylinder oil; four-stroke trunk engines share one sump oil.

Scavenge air pressure and exhaust gas temperature are the primary indicators of combustion quality; a rising exhaust temperature at constant load signals fouling, injection fault or air starvation.

Turbocharger surge is prevented by a minimum flow through the compressor; a fouled air cooler or dirty turbine raises both scavenge temperature and exhaust temperature.

Critical speed is a shaft rotational speed coinciding with a natural torsional frequency; continuous operation within the barred speed range is prohibited.

Propeller law: power varies approximately with speed cubed (P ∝ N³) and thrust with speed squared for a fixed-pitch propeller in calm water.

Fuel oil viscosity at the injector must be held at the maker's figure (commonly 10–15 cSt); viscosity above this causes poor atomisation, below it causes wear from low lubricity.

Purifier bowl throughput is reduced and gravity disc selected so the oil/water interface sits inside the disc stack; incorrect gravity disc causes oil in the water outlet or water carry-over.

A fresh water generator flash evaporator uses jacket water at about 60–80 °C; scale forms above roughly 75 °C, reducing output.

Bilge and ballast pumping arrangements must prevent oil/water backflow into ballast tanks; segregated ballast systems require independent lines.

Air compressor intercooling reduces the work of compression; condensate must be drained from intercoolers and receivers to prevent carry-over into air systems.

Steering gear must be capable of putting the rudder over from 35° one side to 35° the other in not more than 28 seconds with the ship at maximum service speed.

Boiler water is treated to control alkalinity (pH about 10.5–11) and to prevent scale and corrosion; dissolved oxygen is removed by a deaerator and oxygen scavenger.

Overboard discharges from machinery spaces are controlled by the oily water separator 15 ppm alarm and automatic stopping device.

Three-phase power: total active power P = √3 × V_L × I_L × cos φ; apparent power S = √3 × V_L × I_L.

Generator frequency f = (p × N) / 120, where p is the number of poles and N the speed in rpm.

Synchronising requires equal voltage, frequency, phase sequence and phase angle; the incoming machine is brought slightly fast and closed on the 'dark' or 'bright' lamp method.

Load sharing between parallel generators is controlled by the governor (kW) and the excitation system (kVAr); a machine with rising excitation takes more reactive load.

Insulation resistance is measured with a 500 V insulation tester; a minimum of 1 MΩ is commonly required for a 440 V system before energising.

The preferential trip or load shedding system disconnects non-essential loads when a generator overloads, protecting the remaining machines from cascade trip.

PID control: proportional action responds to present error, integral action removes steady-state offset, derivative action responds to rate of change and amplifies noise.

Fail-safe design: alarms are arranged so that loss of power or sensor failure produces an alarm, not a silent failure; watchdog timers detect frozen processors.

The engineer of the watch must not leave the machinery space unattended until relieved by a competent engineer, and must inform the bridge before any manoeuvre affecting propulsion.

Bridge control is transferred only by positive two-way agreement; the telegraph reply confirms the order has been received and is being executed.

Unattended machinery space (UMS) operation requires the dead-man alarm to be reset at intervals not exceeding 30 minutes when the vessel is in UMS mode.

A standing or running watch log records parameters at intervals; trends rather than single readings identify developing faults.

Before any maintenance on a system, isolate it, drain and depressurise it, lock off or tag the isolation, and verify zero energy before work begins.

Planned maintenance is based on running hours or calendar intervals from the maker's manual; condition monitoring (vibration, oil analysis, thermography) sets the interval in condition-based schemes.

Crankcase oil mist detection and bearing temperature monitoring are the principal safeguards against crankcase explosion in diesel engines.

A permit-to-work system is required for enclosed space entry, hot work and work on electrical or pressure systems.

Waterplane area coefficient C_w = A_w / (L × B); block coefficient C_b = volume of displacement / (L × B × d).

Reserve buoyancy is the watertight volume above the waterline; it is what allows a damaged ship to remain afloat.

Free surface effect reduces metacentric height: loss of GM ≈ (i × ρ_liquid) / (ρ_water × Δ), where i is the second moment of area of the free surface.

The inclining experiment determines the lightship KG and displacement; it must be repeated after major structural alterations.

Load line marks: the summer load line is at the assigned freeboard; the tropical mark allows greater draught, the winter mark less.

Damage control: close watertight doors and hatches, isolate the affected compartment, sound the alarm, and report to the bridge before counter-flooding.

Shear force and bending moment diagrams are derived from the load curve; still-water bending plus wave bending must stay within class allowable limits.

A collision bulkhead must be located not less than 5% of ship length and not more than 3 m plus 5% of length from the forward perpendicular.

Fire triangle: fuel, oxygen and heat; removing any one side extinguishes the fire. The tetrahedron adds the uninhibited chemical chain reaction.

Class A fires (solids) use water; class B (flammable liquids) use foam, dry powder or CO₂; class C (gases) use dry powder; class E (electrical) use CO₂ or dry powder, never water.

CO₂ displaces oxygen to below the level supporting combustion; the space must be sealed and evacuation completed before release, and re-entry requires ventilation and atmosphere testing.

Fixed foam systems for machinery spaces are typically applied at a rate calculated to cover the protected area; foam blankets the fuel surface and cools it.

Lifeboat drills: each crew member must participate in at least one abandon-ship drill and one fire drill per month; drills are recorded in the official logbook.

Immersion suit and lifejacket checks include automatic inflation device, retro-reflective tape, whistle and light; lifejackets are stowed at the muster station or cabin.

A fire patrol or detection system must give alarm at the continuously manned control station; the alarm must be audible throughout accommodation and machinery spaces.

Emergency escape breathing devices (EEBD) give about 10–15 minutes of air and are for escape only, not for firefighting.

MARPOL Annex I limits oily water discharge to 15 ppm; the oily water separator must have a 15 ppm alarm and automatic stopping device.

Annex I prohibits any discharge of oil within special areas and within 50 nautical miles of land outside special areas; the Oil Record Book Part I is completed for each operation.

Annex II controls noxious liquid substances by category; Annex III covers packaged harmful substances; Annex IV sewage; Annex V garbage; Annex VI air pollution.

Annex VI sulphur limit is 0.50% m/m globally and 0.10% m/m in Emission Control Areas; compliance may be by low-sulphur fuel or an approved scrubber.

Annex VI NOx Tier limits apply to engines over 130 kW installed after the applicable date; Tier III applies in NOx Emission Control Areas.

Garbage discharge: no plastics anywhere; food waste may be discharged outside 12 nm (comminuted outside 3 nm); Annex V requires a Garbage Record Book and placards.

Ballast water management requires an approved treatment system and a Ballast Water Record Book; the exchange standard is D-1 and the treatment standard D-2.

Oil spill response: stop the source, contain with booms, recover with skimmers or absorbents, notify the coastal state and the flag administration, and record all actions.

SOLAS Chapter I requires a Cargo Ship Safety Construction Certificate, Safety Equipment Certificate and Safety Radio Certificate, each with a specified maximum validity, usually 5 years.

The ISM Code requires a Safety Management System, a Designated Person Ashore, documented procedures and internal audits; the DOC and SMC certificates evidence compliance.

The STCW Convention sets minimum standards of competence and watchkeeping hours; rest hours must be at least 10 hours in any 24 and 77 hours in any 7 days.

MARPOL, Load Line, Tonnage and COLREG certificates are issued by the flag administration or a recognised organisation on its behalf.

Port State Control inspects foreign ships against conventions; a ship may be detained for deficiencies that make it unseaworthy or hazardous.

The annual survey, intermediate survey and special survey cycle is set by the classification society and the flag state; the special survey renews class.

Under COLREG, the stand-on vessel must maintain course and speed until collision risk makes action necessary; the give-way vessel takes early and substantial action.

A near-miss or accident must be reported to the flag administration; serious casualties are investigated under the IMO Casualty Investigation Code.

Thermal efficiency of an ideal Otto cycle η = 1 − 1/r^(γ−1), where r is compression ratio and γ = c_p/c_v.

Diesel cycle efficiency depends on compression ratio, cut-off ratio and γ; higher compression ratio raises efficiency, higher cut-off ratio lowers it.

First law for a steady-flow control volume: Q − W = ṁ[(h₂ − h₁) + ½(v₂² − v₁²) + g(z₂ − z₁)].

Sensible heat Q = m c ΔT; latent heat Q = m L; for water, c ≈ 4.18 kJ/kg·K and latent heat of vaporisation ≈ 2257 kJ/kg at 100 °C.

Ideal gas law pV = mRT; R for air = 0.287 kJ/kg·K; absolute pressure = gauge pressure + atmospheric pressure.

Stress σ = F/A; strain ε = ΔL/L; Young's modulus E = σ/ε; torque transmitted by a shaft T = (π/16) × τ × d³ for a solid circular shaft.

Bending stress σ = M y / I; for a rectangular section I = b h³ / 12 and section modulus Z = b h² / 6.

Heat transfer: conduction Q = k A ΔT / L; convection Q = h A ΔT; the overall heat exchanger duty Q = U A ΔT_lm.