Pancyprian TS Marine Mech. II cheat sheet

Ideal diesel cycle: isentropic compression, constant-pressure heat addition, isentropic expansion, constant-volume heat rejection; thermal efficiency = 1 - (1/r^(k-1)) x [(rho^k - 1)/(k(rho - 1))], where r = compression ratio, rho = cut-off ratio, k = 1.4 for air.

Two-stroke cycle completes one power stroke per revolution; scavenging air must first displace residual gas through exhaust ports or valves. Loop, cross and uniflow scavenging differ in gas flow path; uniflow (exhaust valve) gives the best scavenging efficiency in modern slow-speed engines.

Mean indicated pressure pmi = (indicated work per cycle)/(stroke volume); indicated power = pmi x L x A x n x i, where n = cycles per second and i = number of cylinders. Brake power = indicated power x mechanical efficiency.

Specific fuel consumption (sfc) = fuel mass flow / brake power; typical large two-stroke diesels: 160-175 g/kWh. Raising scavenge air pressure and maximising maximum cylinder pressure (Pmax) improves efficiency.

Compression ratio in slow-speed two-strokes is 12-20:1; firing pressure typically 130-180 bar. Compression pressure must exceed the self-ignition temperature of the fuel (diesel auto-ignition ~250 C at 30-40 bar).

Construction: bedplate, A-frame/columns, cylinder block, cylinder liner, cylinder cover, piston with crown and skirt, crosshead (two-stroke), connecting rod, crankshaft, running gear. Tie rods preload the column/entablature assembly.

Piston rings: top rings carry gas sealing and run hot; oil control ring returns excess lube oil. Ring gap and groove clearance must be within maker's limits; broken rings cause blow-by, high crankcase pressure and scavenge space fires.

Performance monitoring: indicator diagrams (p-V and p-theta) reveal injection timing, Pmax, compression pressure and exhaust valve timing faults; exhaust gas temperature per cylinder and turbocharger speed trends are the primary diagnostic indicators.

Fuel quality per ISO 8217: viscosity (cSt at 50 C), density, sulphur, CCAI, water and sediment. Heavy fuel oil must be heated to the viscosity specified for injection (typically 10-20 cSt at the injector).

Jerk-type fuel pump: plunger driven by cam, helix controls spill point and thus quantity; delivery valve with unloading volume prevents secondary injection and dribble. Timing is set by pump lead or by adjusting the cam/shim.

Common rail and electronic injection allow independent control of injection pressure, timing and duration; pilot and post injection reduce NOx and combustion noise. Injection pressure can exceed 1000 bar in modern medium-speed engines.

Fuel system: settling tank, service tank, transfer pump, purifier/clarifier, heater, viscosity controller, fine filter, high-pressure pump, injector, leak-off. Changeover from HFO to MDO before manoeuvring and before shutdown; follow the maker's temperature ramp.

Lubrication: main lube oil pump, pre-lubrication pump, cooler, filters (auto back-flush), crankcase, sump. System oil for two-strokes is separate from cylinder oil; cylinder oil feed rate is set by sulphur content (BN matching).

Cylinder oil BN selection: BN 40 for low-sulphur fuel (<0.5% S), BN 70 for high-sulphur residual fuel; overbased oil neutralises sulphuric acid from combustion. Too high BN with low-sulphur fuel causes deposits.

Cooling: fresh water (jacket, cylinder heads, air coolers) in a closed circuit with expansion tank, venting, and a sea water circuit via central cooler. Maintain treatment (nitrite/borate) to prevent corrosion and scale; alarm on high temperature and low pressure.

Starting: compressed air at 25-30 bar admitted to air-start valves in firing order; starting air capacity must allow at least 12 consecutive starts for reversible engines (SOLAS II-1). Interlock prevents starting with turning gear engaged.

Reversing: two-stroke engines reverse by shifting the camshaft (fuel and exhaust cams) or by reversing the distributor; four-strokes use a reversible gearbox or controllable-pitch propeller. Interlock prevents fuel injection until reversing is complete.

Governor and safety: overspeed trip, low lube oil pressure trip, high cooling water temperature trip, crankcase oil mist detector, scavenge space fire detection. Remote control from bridge with engine-room override; dead-man alarm if the bridge control is unattended.

Centrifugal pump: head H = (p2 - p1)/(rho g); affinity laws: Q proportional to N, H proportional to N^2, P proportional to N^3. Cavitation occurs when NPSH available < NPSH required; symptoms are noise, vibration and reduced head.

Positive displacement pumps (gear, screw, reciprocating) deliver nearly constant flow against varying pressure; a relief valve is mandatory on the discharge. Never run a centrifugal pump against a closed discharge for long.

Air compressor: two-stage with intercooler; safety valve on each stage, unloading valve, drain traps. Compression is isothermal in theory, adiabatic in practice; intercooling reduces work and moisture. Air receiver must have a relief valve, pressure gauge and drain.

Separator (purifier): bowl speed generates centrifugal force; gravity disc/ring dam selects the interface position. Purifier removes water and solids; clarifier removes solids only. Efficiency depends on temperature (fuel ~98 C, lube oil ~90 C) and flow rate.

Heat exchanger: LMTD method; Q = U A LMTD. Counterflow gives the highest effectiveness. Fouling reduces U; test by temperature difference across the exchanger and by comparing inlet/outlet on both sides.

Steering gear: SOLAS requires two independent power units; main and auxiliary steering gear must be capable of putting the rudder from 35 deg on one side to 35 deg on the other in not more than 28 s with the ship at maximum service speed. Emergency power supply from emergency generator or accumulator.

Steering gear types: electro-hydraulic ram (two rams), rotary vane, and ram-type with variable delivery pumps. Hunting gear provides rudder feedback; follow-up and non-follow-up control modes.

Deck machinery: windlass, mooring winches, capstans, cranes. Brake holding capacity and holding load per IACS; test brakes annually and record. Winch control must have emergency stop and overload protection.

Pump and compressor maintenance: check gland packing/mechanical seal, bearing temperature and vibration, alignment, valve condition, and oil level. Record running hours and plan overhauls by maker's interval.

Three-phase AC: line voltage = sqrt(3) x phase voltage in star; line current = sqrt(3) x phase current in delta. Power P = sqrt(3) x V_L x I_L x cos phi. Insulation resistance measured with a megohmmeter at 500 V DC; minimum acceptable values per maker and class.

Ship distribution: main switchboard, emergency switchboard, section boards, distribution boards. Essential services (steering gear, emergency lighting, fire pump, radio) fed from emergency switchboard with automatic changeover within 45 s per SOLAS.

Generator protection: overcurrent, reverse power, preferential trip, earth fault, over/under voltage and frequency. Parallel operation requires synchronising (voltage, frequency, phase) before closing the breaker; load sharing by governor droop or isochronous control.

Earthing: insulated neutral system common on ships; earth fault detection by insulation monitoring. Single earth fault must not trip essential circuits; locate and clear promptly.

Automation: UMS (unattended machinery space) requires alarms, safety trips, fire detection and bilge level alarms extended to the bridge and duty engineer's cabin. Periodical unattended operation per class rules.

Sensors and instrumentation: PT100/thermocouple for temperature, pressure transmitters (4-20 mA), flow meters, level sensors (float, capacitance, radar). Calibration and loop checks; 4-20 mA signal corresponds to calibrated range.

Alarm system: group alarm, first-up alarm indication, alarm limits, repeat and accept functions. Test alarms periodically; record in the alarm log. Safety systems must fail safe.

Variable frequency drives and soft starters reduce starting current; harmonic distortion and EMC must be considered. Electric propulsion uses cycloconverters or PWM drives with podded propulsors.

Planned maintenance system (PMS): running-hour and calendar-based jobs, condition monitoring, spare parts inventory, defect reporting. Class surveys and maker's intervals set the overhaul schedule.

Condition monitoring: vibration analysis (bearing defects, misalignment, unbalance), oil analysis (wear metals, water, viscosity, TBN), thermography, performance trend analysis and indicator diagrams.

Fault diagnosis logic: define symptom, gather data, compare with baseline, isolate by test, confirm by repair. Common faults: high exhaust temperature (injection, scavenge, turbocharger), high lube oil consumption (rings, liners), low compression (valves, rings).

Crankshaft deflection measurement detects bedplate distortion and bearing wear; readings compared with maker's limits and previous readings. Take with engine cold and at defined positions.

Workshop technology: measurement with micrometer, vernier caliper, dial gauge, feeler gauge; tolerances and fits (clearance, interference, transition); surface finish; torque and stretch measurement for critical bolts (torque wrench, hydraulic tensioner).

Machining and repair: turning, milling, drilling, grinding, welding (SMAW, TIG, MIG), brazing. Repair of worn shafts by metal spraying, sleeving or welding; crack repair by stitching or welding with preheat and post-weld heat treatment.

Non-destructive testing: dye penetrant, magnetic particle, ultrasonic, radiography, eddy current. Use for crack detection in crankshafts, pistons, connecting rods, and welds.

Safety in workshop: machine guards, PPE, lock-out/tag-out before maintenance, permit-to-work for hot work and enclosed spaces, gas freeing and atmosphere testing before entry.

Spare parts and stores: critical spares list per SOLAS/class, minimum stock, identification and preservation; record consumption and reorder levels.

Ship structure: keel, keelson, frames, floors, stringers, longitudinal and transverse framing, bulkheads, decks, double bottom, side shell, collision bulkhead (forward of the engine room). Engine room is bounded by watertight bulkheads and the engine room casing.

Watertight subdivision: SOLAS damage stability requires the ship to survive flooding of specified compartments. Watertight doors in bulkheads must be operable from both sides and from the bridge; drills and records required.

Stability basics: GM = KM - KG; positive GM gives initial stability. GZ curve, righting lever, angle of vanishing stability, free surface effect (reduces GM), and the effect of adding/removing weights.

Free surface effect: FSC = (i x rho_liquid)/(displacement x rho_ship); longitudinal subdivision reduces it. Tank filling levels and slack tanks must be controlled; avoid large free surfaces.

Damage control: damage control plan and booklet posted; compartment boundaries, watertight closures, pumps, bilge system, collision mat, shoring. Engine room bilge system with independent bilge pump and emergency bilge suction.

Flooding response: sound general alarm, muster, locate and isolate, close watertight doors, start emergency bilge pump, shore and plug, monitor list and trim. Report to bridge and company.

Engine room layout: main engine, auxiliary engines, boilers, pumps, purifiers, switchboard, workshop, stores, steering gear compartment (often aft). Escape routes: two independent means of escape from machinery space per SOLAS.

Load line and hull stresses: hogging and sagging, shear force and bending moment; avoid excessive ballast or cargo distribution. Dry docking and inspection of shell, sea chests and sea valves.

MARPOL Annex I (oil): Oil Record Book Part I for machinery space operations, Part II for cargo; 15 ppm bilge alarm and oily water separator; discharge of bilge water only through 15 ppm equipment with automatic stopping; special areas prohibit discharge.

MARPOL Annex IV (sewage): discharge of comminuted and disinfected sewage at >3 nm, untreated at >12 nm, and only when proceeding at not less than 4 knots; holding tank otherwise. Annex V (garbage): garbage record book and management plan.

MARPOL Annex VI (air): sulphur limit 0.50% m/m global, 0.10% in ECAs; NOx Tier limits for new engines; ODS and VOC controls; fuel oil changeover procedure recorded; bunker delivery note retained 3 years.

Ballast water management (BWM Convention): ballast water management plan, record book, treatment system or exchange; exchange efficiency 95% volumetric or 200% flow-through.

Fire safety: fire triangle, classes of fire (A, B, C, D, electrical), fixed systems (CO2, foam, water mist), portable extinguishers, fire main and hydrants, fire control plan, fire and abandon ship drills monthly per SOLAS.

Occupational health: noise (limit 85 dB(A) 8 h; hearing protection above), heat stress, vibration, hazardous substances (COSHH-style assessment), confined space entry with atmosphere testing (O2 20.9%, LEL <1%, H2S/CO limits).

Engine room hazards: rotating machinery, hot surfaces, high pressure fuel (never search with hands; use paper/card), electrical shock, falls, slipping, lifting operations. Permit-to-work for hot work, enclosed spaces, working aloft and electrical isolation.

Personal protective equipment: helmet, safety shoes, gloves, goggles, ear protection, coveralls; rescue equipment and first aid; muster list and emergency duties.

Safety management: ISM Code, safety management system, risk assessment, near-miss reporting, toolbox talks, safety committee, accident investigation and reporting to flag state.

STCW Convention: certification requirements, watchkeeping principles, rest hours (minimum 10 h in 24 h and 77 h in 7 days; may be reduced to 6 h in 24 h if compensated), records of rest, familiarisation and training.

Engine room watch: keep the watch, monitor machinery parameters, respond to alarms, record in the logbook, hand over with a clear briefing; never leave the watch unattended. UMS watch requires periodic rounds and alarm response.

Certificates and documents: International Oil Pollution Prevention (IOPP) certificate, Safety Management Certificate, Safety Construction, Load Line, Tonnage, Minimum Safe Manning Document, Continuous Synopsis Record.

SOLAS chapters relevant to engine room: II-1 (construction, machinery), II-2 (fire), V (safety of navigation), IX (ISM). Class surveys: annual, intermediate, special (5 years), dry docking twice in 5 years.

MARPOL and ISM records: Oil Record Book entries, garbage record book, ballast water record book, bunker delivery notes, engine room logbook, alarm and maintenance records; retained for inspection by port state control.

Port state control: inspection of certificates, ORB, ISM, fire and safety equipment, pollution prevention equipment; deficiencies may lead to detention. Paris and Tokyo MOU regimes.

Engine room administration: logbook entries, maintenance records, spare parts inventory, fuel and lube oil consumption records, stores requisitions, handover notes, defect list and planned maintenance system updates.

Emergency procedures: abandon ship, fire, flooding, blackout, steering failure; muster list, emergency generator start, emergency fire pump, emergency steering drills. Records of drills required.

Fatigue and fitness for duty: alcohol limit, medical fitness certificate, rest management; report unfit for duty and follow company policy.