Glossary — engineering

Main and auxiliary machinery, fuel systems, electrical, automation, watchkeeping in the engine control room.

114 terms in this category.

• 15 ppm Bilge Alarm
  An automatic alarm fitted to an oily water separator that stops overboard discharge when oil content exceeds 15 parts per million.
• Abrasive Blast Cleaning
  Surface preparation by abrasive grit; standards Sa 1, Sa 2, Sa 2.5, Sa 3 per ISO 8501.
• Ammonia as Marine Fuel
  Carbon-free fuel under development for two-stroke engines; key challenges are toxicity, NOx, and ammonia slip.
• Angle of Vanishing Stability
  Heel angle at which the GZ righting arm becomes zero — beyond which the ship will capsize.
• Antifouling Coating
  Hull coating slowing or preventing biofouling; modern systems are silicone-based (foul-release) or copper/zinc biocidal.
• Autonomous Underwater Vehicle (AUV)
  Untethered, programmable underwater vehicle for survey work — typically hydrographic, environmental, or military.
• Auxiliary Engine (AE)
  A diesel generator engine providing electrical power for shipboard systems independent of the main engine.
• Azimuth Thruster
  A propulsion unit that can rotate 360 degrees, providing both thrust and steering without a conventional rudder.
• Ballast Water Standard D-1
  Ballast water exchange standard requiring at least 95% volume exchange in deep ocean water.
• Ballast Water Standard D-2
  Performance standard limiting viable organisms in discharged ballast; met by an approved ballast water management system.
• Bilge
  The lowest interior space of a vessel where leakage, condensation, and drainage water collects; must be pumped out regularly.
• Biofouling Guidelines
  IMO guidelines for the control and management of ships' biofouling to minimise transfer of invasive aquatic species.
• Bollard Pull (BP)
  Static towing force a tug can exert measured against a fixed bollard; primary spec for tugs (typically 30–100 t for harbour, 150–300 t for AHTS).
• Bow Thruster
  A transverse propulsion unit fitted in a tunnel through the bow section to improve low-speed manoeuvrability in port.
• Bridge Alarm
  An alarm system on UMS vessels that channels all critical engine room and safety alarms to the navigating bridge when the engine room is unmanned.
• Bulkhead
  Vertical partition dividing a ship into watertight compartments.
• Bunker
  Fuel oil carried aboard and consumed by a ship's main and auxiliary engines; also refers to the act of taking on fuel.
• Bunker Delivery Note (BDN)
  Document recording details of fuel oil delivered, including density, viscosity, sulphur content, and supplier ID.
• Cargo Pump
  A large-capacity pump on a tanker used to discharge liquid cargo from cargo tanks to shore or to another vessel.
• Closed-Loop Scrubber (EGCS)
  Exhaust gas cleaning system that uses caustic soda (NaOH) in a closed water loop to remove SOx; sludge stored aboard for shore disposal.
• Collision Bulkhead
  Forward-most watertight bulkhead designed to limit flooding from bow damage.
• Common-Rail Injection
  Fuel-injection system where pressurised fuel is held in a high-pressure rail and injected per-cylinder via electronically controlled injectors.
• Continuous Survey Machinery (CMS)
  Class arrangement allowing machinery items to be surveyed in rotation by the chief engineer rather than in one yard period.
• Controllable Pitch Propeller (CPP)
  A propeller whose blade pitch can be varied in service, allowing speed and thrust control without changing engine rotation direction.
• Crankcase
  The lower enclosed section of an engine housing the crankshaft, connecting rods, and bearing lubrication system.
• Crude Oil Washing (COW)
  A tank cleaning method using crude oil cargo as the washing medium to dissolve and remove waxy residue from tank surfaces.
• Damage Stability
  Stability of a ship after one or more compartments are flooded; assessed deterministically (older rules) or probabilistically (SOLAS II-1 Reg. 6).
• Damaged Waterline
  Equilibrium waterline after damage flooding; must remain below margin line / bulkhead deck for SOLAS compliance.
• Double Bottom
  Twin layer of shell plating with the inner-bottom forming the cargo hold or tank floor; required on most cargo vessels for damage stability and ballast.
• Drydocking Frequency
  Standard 5-yearly cycle with one intermediate drydocking allowed up to 7.5 years for certain ship types under in-water survey schemes.
• Dynamic Positioning (DP)
  A computer-controlled system that automatically maintains a vessel's position and heading using thrusters, without anchoring.
• Emergency Fire Pump
  A self-contained fire pump located outside the machinery space, capable of supplying fire mains if the main pumps are disabled.
• Emergency Generator
  A self-contained standby generator automatically supplying essential electrical power to safety systems if the main supply fails.
• Energy Efficiency Design Index (EEDI)
  Design-phase efficiency index (g CO2 per t·nm) required for newbuilds since 2013; tightens in successive phases.
• Energy Efficiency Existing Ship Index (EEXI)
  One-off retroactive efficiency index applied to ships built before EEDI; effective 2023.
• Exhaust Gas Cleaning System (EGCS)
  A device fitted in the exhaust line that removes sulfur oxides from engine gases, allowing use of high-sulfur HFO under IMO 2020.
• Exhaust Gas Cleaning System (EGCS)
  Scrubber system reducing SOx from exhaust gas to comply with MARPOL Annex VI without using low-sulphur fuel.
• Exhaust Gas Economiser (EGE)
  Heat exchanger in the funnel that recovers waste heat from main-engine exhaust to generate steam.
• Exhaust Gas Recirculation (EGR)
  NOx-reduction technique that recirculates a portion of exhaust gas back into the engine intake, lowering combustion peak temperature.
• FAME / Biofuel
  Fatty Acid Methyl Ester biofuel blended into marine fuels; ISO 8217:2017 permits up to 7% (B7).
• Finnish-Swedish Ice Class
  Ice class IA Super, IA, IB, IC, II, III used in the Baltic; controls fairway dues and icebreaker assistance order.
• Fixed Pitch Propeller (FPP)
  A propeller with blades cast at a fixed angle to the hub; speed and direction are changed by varying engine rpm and rotation.
• Four-Stroke Engine
  An internal combustion engine requiring four piston strokes per cycle, widely used as medium-speed auxiliary and propulsion engines.
• Free Surface Correction (FSC)
  Reduction in effective GM caused by liquid moving in a slack tank; subtracted from solid GM to give fluid GM.
• Fresh Water Generator (FWG)
  A distillation unit using main engine jacket water waste heat to evaporate and condense seawater into fresh water at sea.
• Generator Set (genset)
  A diesel-electric power unit installed in a ship's hold or on deck to supply electrical power to reefer containers.
• Graving Dock
  Permanent excavated dock with a gate; fills with water to receive the ship, then is pumped dry for hull work.
• Hawse Pipe
  Tube through which the anchor chain runs from windlass to the side of the bow.
• Heavy Fuel Oil (HFO)
  Residual fuel oil with high viscosity and sulfur content, historically the primary bunker fuel for ocean-going vessels.
• Hogging
  Longitudinal hull bending where the middle is supported by a wave crest while the ends sag.
• Hopper Tank
  Sloped wing tank along the hold bottom corners on a bulker; aids cargo flow during discharge.
• Hull Stress Monitoring System (HSMS)
  Strain gauges + accelerometers + decision-support software to warn when hull-girder loads approach class limits.
• Hybrid Scrubber (EGCS)
  Scrubber that can switch between open- and closed-loop modes depending on local discharge regulations.
• IACS Polar Class
  Seven-tier ice class (PC1–PC7) under IACS UR I assigning ice-going capability from year-round in all polar waters (PC1) to summer-only thin first-year ice (PC7).
• Impressed Current Cathodic Protection (ICCP)
  Active corrosion protection injecting low-voltage DC into the hull via inert anodes; used on most large vessels.
• Inert Gas System (IGS)
  A system supplying inert gas (flue gas or nitrogen) to tanker cargo tanks to maintain an oxygen-deficient atmosphere and prevent explosion.
• Intact Stability Code (IS Code)
  IMO mandatory code for intact stability of all ships >24 m, including weather criterion and severe wind & rolling.
• Intermediate Fuel Oil (IFO)
  A blend of heavy residual and distillate fuel oil with viscosity typically 180 or 380 cSt, used as main engine bunker.
• ISO 8217
  International standard specifying marine fuel grades — distillates (DMA, DMB, DMZ) and residuals (RMA, RMB, RMD, RME, RMG, RMK).
• Jacking Gear
  A reduction-gear device coupled to the engine flywheel used to slowly turn the engine by hand or motor for inspection.
• Kort Nozzle
  Cylindrical duct around a propeller that increases bollard pull at low speed; common on tugs, fishing vessels, and OSVs.
• List vs Loll
  List = heel from asymmetric weight distribution (positive GM). Loll = heel from negative GM with the ship oscillating about an angle either side of upright.
• LNG Bunkering
  Transfer of LNG fuel ship-to-ship, truck-to-ship, or terminal-to-ship; covered by IGF Code and ISO/TS 18683.
• Longitudinal Stiffener
  Long, thin reinforcing member running fore-and-aft along plating to resist bending and buckling.
• Main Engine (ME)
  The primary propulsion engine driving the ship's propeller shaft, typically a large slow-speed two-stroke diesel on cargo ships.
• Marine Diesel Oil (MDO)
  A distillate fuel oil with low sulfur content, used in auxiliary engines and during port operations where ECA rules apply.
• MARPOL Bunker Sample
  Representative sample drawn at the bunker manifold during delivery, sealed and retained for 12 months.
• Mast Riser
  A large-diameter high-velocity vent pipe fitted to a tanker's mast to discharge cargo vapours safely above ignition sources.
• Methanol as Marine Fuel
  Liquid alcohol fuel adopted by some newbuild container and tanker fleets; bunkered at ambient temperature, simpler infrastructure than LNG.
• Moonpool
  Vertical opening through the hull of an offshore vessel allowing equipment to be lowered from a sheltered indoor location.
• NOx Tier III
  Strictest IMO NOx limit (~3.4 g/kWh at 130 rpm); applies to engines >130 kW installed on ships built ≥2016 trading in NOx ECAs.
• Oil Discharge Monitoring and Control System (ODMCS)
  Equipment on oil tankers that continuously monitors the oil content and flow rate of overboard discharges to ensure MARPOL compliance.
• Oil Mist Detector (OMD)
  A crankcase monitoring device that samples air from each crankcase compartment and alarms if oil mist concentration reaches explosive levels.
• Oily Water Separator (OWS)
  Equipment that separates oil from bilge water to reduce oil content to 15 ppm before overboard discharge under MARPOL.
• Open-Loop Scrubber (EGCS)
  Exhaust gas cleaning system that uses seawater as the alkali source to remove SOx, then discharges treated wash water overboard.
• Performance Standard for Protective Coatings (PSPC)
  IMO standard for coatings in ballast tanks and double-side skin spaces — surface prep Sa 2.5, target life 15 yr.
• Pressure/Vacuum Valve (P/V valve)
  A safety valve on a cargo tank vent that opens at set over- or under-pressure limits to protect the tank structure.
• Propeller Cavitation
  Formation and collapse of vapour bubbles on propeller blades due to local pressure dropping below water vapour pressure.
• Purifier
  A centrifugal separator that removes water and solid contaminants from fuel or lubricating oil before engine use.
• Reefer Container
  A refrigerated ISO container with an integral refrigeration unit maintaining controlled temperatures for perishable cargo.
• Remotely Operated Vehicle (ROV)
  Tethered underwater robot used for inspection, repair, and intervention work, typically operated from an MPSV or DSV.
• Sacrificial Anode
  Block of zinc or aluminium attached to the hull that corrodes preferentially, protecting steel; used in addition to or instead of ICCP.
• Sagging
  Longitudinal hull bending where the middle is unsupported between two wave crests, putting the deck in compression and the bottom in tension.
• Scantlings
  Dimensions (thickness, depth, spacing) of structural members — plating, frames, stiffeners, girders — set by class rules.
• Scavenge Air
  Pressurised air supplied to the cylinder of a two-stroke diesel engine to expel exhaust gases and supply fresh charge for combustion.
• Scavenge Fire
  Fire in the scavenge air space of a two-stroke crosshead engine, ignited by leaking fuel + carbon deposits + scavenge air.
• Selective Catalytic Reduction (SCR)
  Exhaust after-treatment that injects urea into hot exhaust gas, converting NOx to N2 and water on a vanadium-titanium catalyst.
• Sewage Treatment Plant (STP)
  A biological or chemical system treating shipboard sewage to standards permitting overboard discharge under MARPOL Annex IV.
• Shaft Alley
  The enclosed tunnel running through the stern of the ship enclosing the propeller shaft from the engine room to the stern tube.
• Shell Plating
  Outer steel skin of the hull from keel to deck edge.
• Slamming
  Impact of the bow re-entering the water after pitching out, causing localised pressure spikes on the forefoot and forward bottom.
• Slop Tank
  A dedicated tank on tankers used to collect cargo residues and tank washing water, allowing oil-water separation before discharge.
• Springing
  Steady-state hull-girder resonance excited by encounter waves at or near the natural frequency.
• Starting Air Receiver
  A pressure vessel storing compressed air at 30 bar used to crank and start the main engine and diesel generators.
• Stern Tube
  The watertight bearing assembly through which the propeller shaft passes through the hull from the engine room to the propeller.
• Syncrolift
  Mechanical ship-lift platform raising vessels onto land for transfer to repair berths; used by smaller yards.
• Tail Shaft
  Aftermost length of the propeller shaft, running through the stern tube to the propeller; subject to bearing wear and torsional fatigue.
• Tank Cleaning
  The process of removing cargo residues and gas from cargo tanks using water, chemicals, or crude oil washing prior to loading a new cargo.
• Topside Tank
  Triangular tank in upper corner of a bulk carrier hold; carries ballast and reduces free surface of grain cargo.
• Trim and Stability Booklet
  Approved booklet on board summarising loading conditions, hydrostatic data, and stability criteria compliance.
• Turbocharger (TC)
  A device driven by exhaust gas that compresses intake air to increase diesel engine power output and fuel efficiency.
• Turbocharger Surge
  An abnormal flow reversal in a turbocharger compressor, evidenced by a loud banging or barking noise, caused by sudden load changes.
• Turning Gear
  An electric motor-driven gear unit that slowly rotates the main engine crankshaft for maintenance, cooling-down, or warming-through.
• Two-Stroke Engine
  A type of internal combustion engine completing the power cycle in a single up-and-down piston stroke, common in large slow-speed marine main engines.
• Ultra Low Sulphur Fuel Oil (ULSFO)
  Residual marine fuel with ≤ 0.10% sulphur, used to meet Emission Control Area limits.
• Ultrasonic Thickness Measurement (UTM)
  Non-destructive ultrasonic gauging of plate thickness to monitor wastage; required at intermediate / renewal class surveys.
• Unattended Machinery Space (UMS)
  A classification notation permitting the engine room to operate without a watchkeeper at night, subject to enhanced alarms and automation.
• Unmanned Machinery Space (UMS)
  Engine room operated without engineer watch present, relying on automation, alarms, and a duty engineer on call.
• Very Low Sulfur Fuel Oil (VLSFO)
  Fuel oil with a sulfur content of 0.50% m/m or less, required globally under IMO 2020 sulfur cap regulations.
• Voith-Schneider Propeller (VSP)
  Cycloidal propeller producing thrust in any direction by varying blade pitch as the disc rotates; common on tractor tugs.
• Weather Criterion
  Stability criterion checking that a ship can withstand a steady beam wind plus a sudden gust while rolling — Part A 2.3 of the IS Code.
• Web Frame
  Heavy transverse frame, larger than ordinary frames, providing structural support typically every 3–5 frame spaces.
• Whipping
  Transient hull-girder vibration triggered by a slam, decaying over several oscillations.
• Wing Tank
  Tank running along the side of a vessel, often a ballast tank on bulk carriers or a side cargo tank on tankers.