Extended Operational and Trade Vocabulary

Marine Engine Maintenance, Overhaul, and Condition Monitoring glossary

Terminology of marine engine maintenance and condition monitoring: turbocharger families such as ABB TPL, TPS and A-series with their overhaul intervals, two-stage Power2 and Powerturbo waste-heat systems, shop acceptance tests verifying SFOC and NOx under ISO 3046, and the running-hour and cartridge-renewal schedules governing two-stroke and medium-speed engine overhaul.

312 defined terms.

Showing 250 on this page (page 1 of 2).

A

Aalborg AQ Composite Boiler: Combined exhaust gas and oil-fired boiler from Aalborg used on tankers and bulk carriers for steam generation at sea and in port.
Aalborg MissionSky: Steam atomization auxiliary boiler design from Alfa Laval Aalborg with reduced NOx emissions and high turn-down ratio.
Aalborg OL Boiler: Vertical fire-tube auxiliary boiler in the Mission OL series, requiring periodic descaling and refractory inspection at 8,000-hour intervals.
Aalborg OS Boiler: Oil-fired auxiliary steam boiler from Alfa Laval Aalborg in the Mission OS series, with annual fireside inspection and triennial waterside survey.
ABB A-Series Turbocharger: ABB A100, A200, and A300 axial turbochargers used on MAN ME-C and Wartsila RT-flex engines, with cartridge replacement around 24,000 hours.
ABB Power2 800: Two-stage high-pressure turbocharging system from ABB enabling Miller cycle operation and Tier III NOx compliance on medium-speed engines.
ABB Powerturbo: ABB exhaust gas power turbine system that recovers waste heat energy from the exhaust stream to drive a generator or feed the propeller shaft.
ABB TPL Turbocharger: Single-stage axial-flow turbocharger family from ABB Turbocharging for large two-stroke and medium-speed engines, with overhaul intervals typically aligned with 16,000 to 24,000 running hours.
ABB TPS Turbocharger: Radial-flow turbocharger family from ABB for medium and high-speed four-stroke engines, with bearing renewal commonly recommended at 12,000 to 16,000 hours.
Acceptance test: Factory or shop trial to verify contractual performance.
AFC Fully Automatic Combustion: Aalborg burner control concept enabling unattended boiler operation with continuous flame monitoring and fuel-air ratio trim.
Alkaline Cylinder Oil: Cylinder lubricant formulated with overbased calcium sulfonate or phenate detergents to neutralize sulfuric acid formed from high-sulfur fuel combustion.
Alpha Lubricator: MAN ES electronically controlled cylinder lubrication system relevant to the prime mover driving the shaft line.
Aluminium Wear: Element measured at parts per million in lube oil analysis by ICP spectrometry, indicating piston skirt or bearing cage wear.
Anac Marine: TotalEnergies lube oil condition monitoring laboratory service providing trend analysis for system oil and cylinder drain oil samples.
ANSI/AGMA 9000: American Gear Manufacturers Association standard for gear inspection used in reduction gearbox alignment and tooth wear assessment.
API CF Specification: American Petroleum Institute classification covering severe-duty diesel engine oils suitable for older indirect-injection medium-speed engines.
API CI-4 Specification: American Petroleum Institute classification for heavy-duty diesel engine oils compatible with EGR-equipped four-stroke engines.
Articulated Connecting Rod: Vee engine arrangement where the slave rod attaches to the master rod, common in MaK and certain Pielstick PC designs, requiring matched-pair inspection.
Ash content: Inorganic residue after combustion of a fuel sample, measured per ISO 6245, capped at 0.100% m/m for most residual grades.
ASTM D2896: Standard test method for Base Number of petroleum products by potentiometric perchloric acid titration, the reference method for fresh cylinder oils.
ASTM D445: Standard test method for kinematic viscosity of transparent and opaque liquids.
ASTM D4739: Base number determination by potentiometric titration.
ASTM D5185: Standard test method for multielement determination of used and unused lubricating oils by ICP-OES, the primary wear metals method.
ASTM D664: Standard test method for acid number of petroleum products by potentiometric titration.
Auxpac: Wartsila packaged auxiliary generator set offered with 20, 26, and 32 series engines for shipboard electrical power, with major overhauls at 24,000 hours.
Axial Clearance: Crosshead and crankshaft thrust clearance measurement taken during dry-dock condition surveys to verify thrust bearing wear within OEM limits.
Axial Vibration: Longitudinal oscillation of the crankshaft along its axis monitored by ICVA sensors, with elevated levels indicating thrust bearing damage or torsional resonance.

B

Babbitt White Metal: Tin-based bearing lining alloy used in main bearings, crosshead bearings, and crankpin bearings, examined under magnification during crankcase inspections.
Balance Grade G2.5: ISO 1940 quality grade for turbines, turbocompressors, and high-speed rotors including turbocharger rotors after blade replacement.
Balance Grade G6.3: ISO 1940 quality grade for rotating machinery applicable to standard marine pumps and fans, expressed as permissible residual unbalance.
Base Number BN 100: High-alkalinity cylinder lubricant historically used for HFO with sulfur content of 2 to 3.5 percent, now niche for non-compliant operations.
Base Number BN 140: Extreme high-alkalinity cylinder oil developed for very high-sulfur residual fuels, largely obsolete post IMO 2020 except for scrubber-equipped ships.
Base Number BN 40: Cylinder lubricant alkalinity reserve suitable for low-sulfur distillate fuels and LSFO compliant with IMO 2020 sulfur cap.
Base Number BN 70: Cylinder oil alkalinity grade traditionally used for medium-sulfur intermediate fuel oils up to about 1.5 percent sulfur.
Bearing Oil Film Thickness: Calculated minimum oil film in hydrodynamic journal bearings, monitored indirectly through inlet temperature, pressure, and ovality measurement.
Bedplate: Steel base on a tank container frame supporting the pressure vessel.
Bently Nevada 3500: Rack-based vibration and condition monitoring system from Baker Hughes widely deployed on shipboard turbomachinery and main engine shaft lines.
BHP Brake Horsepower: Power measured at the engine output flange by absorption dynamometer, expressed in metric horsepower or kilowatts.
BHRP Burner Head Replacement: Periodic boiler maintenance task involving renewal of atomizer tip, swirler, and diffuser cone to maintain combustion efficiency.
Big-End Bearing: Crankpin bearing on the four-stroke connecting rod inspected during major overhauls for white-metal wipe, fatigue cracks, and clearance.
Blowdown Bottom: Boiler discharge procedure removing sludge from the lowest mud drum or shell, typically performed at the start of each watch.
Blowdown Surface: Continuous or intermittent skimming of boiler water at the working level to control total dissolved solids and chloride concentration.
Blower Side Cleaning: Turbocharger compressor wheel water washing carried out during operation by injecting fresh water at the air intake to remove fouling deposits.
Bore Cooling: Cylinder liner upper-belt cooling channels drilled axially through the collar to maintain controlled liner wall temperature and avoid cold corrosion.
BP MES: BP Marine engine oil condition monitoring service providing scheduled lube oil analysis with online trending and depletion alerts.
Brake Power Pb: Net useful power delivered at the engine coupling after deducting mechanical losses, reported per ISO 3046-1.
Bridge Gauge: Crankshaft web deflection measuring tool spanning two adjacent webs with a dial indicator at the centre, used at TDC and BDC of each unit.

C

Camshaft Inspection: Periodic check of cam profile wear, follower roller condition, and bearing clearance, typically every 16,000 hours on cam-driven two-stroke engines.
Carbon Trumpet: Hard carbon deposit growing inward from the upper cylinder liner above the piston top ring, capable of scoring rings and causing micro-seizure.
Castrol Cyltest: Castrol shipboard test kit for monitoring cylinder drain oil residual BN and iron content as a feed-rate optimization tool.
Caterpillar 3500: Caterpillar medium-speed four-stroke engine series widely used as marine auxiliary and propulsion, with major overhaul intervals around 24,000 hours.
Caterpillar 3600: Caterpillar in-line and vee medium-speed engine series for marine main propulsion, with top-end overhaul at 12,000 hours and major at 36,000 hours.
Caterpillar C175: Caterpillar vee high-speed engine series for marine propulsion and gensets, with major overhauls scheduled near 30,000 hours.
Caterpillar C32: High speed marine diesel generator engine common on offshore vessels.
Cathodic protection survey: Inspection of sacrificial anodes and impressed current systems.
CBM Condition-Based Maintenance: Maintenance strategy where intervention is triggered by measured machine condition rather than calendar or hours alone.
Cetane index: Calculated ignition quality indicator for distillate fuels, per ASTM D976 or D4737.
Chevron LubeWatch: Chevron lube oil condition monitoring laboratory service for marine system oils, cylinder drain oils, and hydraulic oils.
Chromium Wear: Element tracked in lube oil analysis at parts per million by ICP indicating piston ring face wear or chrome-plated liner wear.
Clearance Volume: Combustion space above piston at TDC determining compression ratio, verified after liner replacement by lead-wire crush measurement.
Cold Corrosion: Sulfuric acid attack on cylinder liner surfaces when wall temperature drops below the acid dewpoint, common at part-load slow steaming.
Compression Pressure Pcomp: Cylinder pressure at TDC measured without combustion, used to diagnose ring blowby, valve leakage, and worn liner.
Conductivity: Electrical conductivity of seawater, used in the CTD to derive salinity.
Connecting rod: Rod between piston and crankshaft.
Copper Wear: Element measured in lube oil at parts per million indicating bearing shell or oil cooler tube degradation.
Crankcase explosion: Ignition of oil mist in the crankcase, mitigated by oil mist detection and explosion relief doors.
Crankcase Inspection: 750-hour and 1,500-hour walk-in survey of main bearings, crosshead pins, crankpins, guides, and tie-rod nuts on two-stroke engines.
Crankshaft deflection: Web-deflection measurement indicating alignment.
Crankshaft Polishing: In-situ journal restoration using emery cloth and dedicated polishing kits to remove minor scoring without machining.
Crankshaft Run-Out: Dial indicator measurement of journal eccentricity along the shaft length, performed during major dry-dock surveys.
Crosshead Bearing: Lubricated sliding bearing on the two-stroke piston rod's lower end, supplied by a high-pressure oil pump and inspected at 8,000-hour intervals.
CSR Continuous Service Rating: Engine output corresponding to normal sea-going operation, usually 85 to 90 percent of MCR for slow-speed propulsion plants.
Cummins QSK: Cummins high-speed four-stroke engine family used as marine auxiliary, with top-end overhaul at 12,000 hours.
Cycle Beta Test: Mean cylinder pressure indicator card analysis using electronic indicators such as the Doctor system from Icon Research or the CYLDET from Cyldet.
CYLDET: Cyldet electronic cylinder pressure indicator system used to record peak pressure, compression pressure, and indicated power on slow-speed engines.
Cylinder Condition Monitoring: Combined assessment of scrape-down oil iron content, scavenge port inspection, and indicator diagrams to determine liner and ring condition.
Cylinder Drain Oil: Spent cylinder lubricant collected from the scavenge box drain, sampled for iron content and residual BN at weekly intervals.
Cylinder Head: Combustion chamber upper closure containing exhaust valves and fuel injectors, removed every 16,000 to 24,000 hours for water-space cleaning and valve renewal.
Cylinder liner: Replaceable cast-iron liner forming combustion chamber wall.

D

Daihatsu DC series: Daihatsu legacy medium-speed marine diesel family preceding the DK generation.
Daihatsu DK Series: Four-stroke medium-speed marine engines from Daihatsu Diesel widely used as auxiliary gensets.
Deflection Gauge: Dial micrometer instrument fitted between crankshaft webs to measure axial gap variation around one full revolution.
Deposits: Combustion residue and ash accumulation on piston crown, ring grooves, and exhaust valve seats indicating fuel quality and lubrication issues.
Derating: Continuous operation at reduced MCR to lower SFOC and CO2 emissions, often supported by tuning kits and turbocharger cut-out.
Detergency: Lube oil additive function dispersing combustion soot and varnish precursors, evaluated by spot test ASTM D7899.
Dewpoint Corrosion: Acid attack on cooler economiser tubes and liner walls where exhaust gas or wall temperature falls below the sulfuric acid dewpoint.
Dial Micrometer: High-resolution measuring instrument used for web deflections, bearing clearances, and crankshaft run-out.
Diesel Knock: Audible combustion roughness arising from delayed ignition, monitored by indicator cards and accelerometer signatures.
Dry Cleaning Turbocharger: Crushed nutshell or specialised granular media injected into the turbine inlet to remove deposits without water injection.

E

EGB Exhaust Gas Boiler: Auxiliary boiler recovering heat from main engine exhaust for steam generation at sea, with annual gas-side and waterside surveys.
EGR (Exhaust Gas Recirculation): NOx control method per MARPOL Annex VI Tier III.
Electronic Indicator: Pressure transducer-based recording system replacing mechanical indicator cards, models include Icon Doctor, Lemag PREMET, and Kistler 6613.
Engine Load Diagram: Torque-speed envelope defined by MAN, Wartsila, and other OEMs setting permissible continuous and overload operating areas.
Engine Margin: Power reserve typically 10 percent between contracted CSR and MCR allowing for engine deterioration.
Engine Performance Test: Periodic measurement of pressure, temperature, fuel rack, and turbocharger speed across the load range to detect degradation.
Exhaust valve cage: Removable cylinder-head housing for exhaust valve.
Exhaust Valve Spindle: Nimonic-alloy exhaust valve with stellite-coated seat, rotated by a vane wheel to equalise wear.
ExxonMobil Signum: ExxonMobil's used oil analysis service for marine lubricants providing online portal access to trended results and recommendations.

F

FAS Fuel Aerosol & Sludge: Combustion-derived liquid and solid contaminants found in scavenge spaces during inspections indicating injection or atomisation issues.
Fe Iron Content: Cylinder drain oil iron concentration in parts per million tracked to detect abnormal wear, target typically below 200 ppm.
Feed Rate: Cylinder oil dosing in grams per kilowatt hour, typically 0.6 to 1.5 g/kWh on modern ME-C and RT-flex engines using Alpha or Pulse Lubrication.
FIA Fuel Ignition Analyser: Laboratory instrument from FIA-Tech or similar used to assess fuel ignition quality for heavy fuel oils per IP 541.
Filter Backflush: Automated cleaning of self-cleaning lube oil filters such as Boll & Kirch or Alfa Laval Moatti.
Fluke Pruftechnik: Pruftechnik vibration analysers and alignment systems now under the Fluke brand, used for shaft alignment and route-based vibration monitoring.
Follow-Up Steering: Steering gear control mode where rudder angle follows wheel input continuously, contrasted with non-follow-up jog control.
Four-Stroke Major Overhaul: Complete top and bottom-end renewal at approximately 24,000 to 30,000 hours on medium-speed engines, including head, piston, big-end, and main bearings.
Four-Stroke Minor Overhaul: Cylinder head, piston ring, and injector renewal carried out at about 8,000 to 12,000 hours.
Fuel Index: Fuel pump rack position indicator giving an indirect measure of cylinder fuel quantity, monitored during performance tests.
Fuel Valve: High-pressure fuel injector with multi-hole nozzle tip overhauled at 2,000 to 4,000 hours on slow-speed engines.

G

Gas Side Cleaning: Removal of carbon and ash deposits from turbocharger turbine blades by water washing or grit blasting.
GBM Gas-Based Mode: Operation mode of MAN ME-GI dual-fuel engines using natural gas as primary fuel and pilot diesel for ignition.
Graviner Mk7: Kidde Graviner oil mist detector system fitted to crankcases of two-stroke and large four-stroke engines for explosion prevention.
Guide Shoe: Crosshead component sliding on guide rails, inspected during crankcase surveys for wear of bronze running surface.

H

Hans Jensen SIP: Swirl Injection Principle developed by Hans Jensen Lubricators, distributing cylinder oil through angled nozzles to coat the liner via scavenge air swirl.
HCU Hydraulic Cylinder Unit: ME-C and ME-B fuel injection actuator block containing fuel and exhaust valve servo cylinders, with fine filter renewal at 1,500-hour intervals.
Heel Spring: Exhaust valve spring fitted to MAN B&W exhaust valves, renewed at major valve overhauls.
HEMOS: MAN PrimeServ historical engine monitoring and operating system collecting performance data for trend analysis.
High-Pressure Pipe: Common-rail or jerk-pump fuel pipe rated for above 600 bar, inspected for cracks and double-wall integrity each overhaul.
HiMSEN H21: HSD Engine (formerly Hyundai HiMSEN) 210 mm bore medium-speed engine widely used as marine genset.
HiMSEN H32: HSD Engine 320 mm bore medium-speed engine used in marine auxiliary and small propulsion applications.
HiMSEN H35: HSD Engine 350 mm bore engine for medium-power marine main propulsion and large auxiliary duty.
Hot Corrosion: Sulphidation attack on exhaust valve seats and turbocharger nozzle rings caused by sodium and vanadium compounds at elevated temperature.
Hydram Steering Gear: Hydraulic ram-type steering actuator using a Rapson slide mechanism, common on tankers and bulk carriers.
Hydraulic Tightening: Use of calibrated stud tensioners to apply controlled bolt preload on main bearings, cylinder heads, and tie rods.
Hydrazine: Boiler water oxygen scavenger dosed alongside ammonia for pH control, increasingly replaced by carbohydrazide.

I

IACS UR M28: International Association of Classification Societies Unified Requirement on crankshaft alignment and web deflection limits.
IACS UR S5: IACS Unified Requirement for steering gear specifying performance, redundancy, and survey criteria.
ICP Spectrometry: Inductively coupled plasma atomic emission spectroscopy used for wear metal and additive element analysis per ASTM D5185.
ICVA Imbalance and Vibration Analysis: Inspection regime combining torsional, axial, and lateral vibration measurement to diagnose rotor and shaft line condition.
Imo Pump: Three-screw positive displacement pump from Colfax Imo used as lube oil main and stand-by pump.
In-Situ Honing: Cylinder liner restoration technique using portable hones to recondition the running surface without liner removal.
In-water cleaning (IWC): Cleaning of ships' underwater surfaces while afloat.
Indicated Power Pi: Power developed inside the cylinder calculated from indicator diagram mean effective pressure and engine speed.
Indicator diagram: Pressure crank angle trace from peak pressure indicator used to assess cylinder condition.
Injection timing: Crank-angle reference for start of injection.
Iron content: Concentration of iron in scrape-down or system oil samples, used as a primary wear indicator.
ISO 10816: International standard on mechanical vibration evaluation by measurement on non-rotating parts, the bearing housing seismic standard.
ISO 15550: International standard specifying methods for determination of engine power and reference conditions.
ISO 1940: International standard on balance quality requirements for rotors in a constant rigid state, defining grades from G0.4 to G4000.
ISO 20816: Updated international standard series superseding ISO 10816 and ISO 7919 for vibration measurement and evaluation of machine sets.
ISO 3046: International standard for reciprocating internal combustion engines covering performance, declarations, ratings, and shop tests.
ISO 4406: International standard for fluid contamination cleanliness coding by particle count at 4, 6, and 14 micrometre thresholds.
ISO 7919: Mechanical vibration of non-reciprocating machinery shafts.
ISO 8217: International standard for marine fuel oil specifications.

J

Jacket cooling water: HT cooling loop around cylinder block.
Jerk-Pump Injection: Mechanical cam-driven fuel injection used on MC-C, RTA, and older medium-speed engines, with timing fixed by cam profile.
Journal Examination: Visual and microscopic inspection of crankpin and main bearing journals for scoring, ovality, and fretting during crankcase surveys.

K

Karl Fischer titration: Coulometric or volumetric water determination per ISO 12937 or ASTM D6304.
Kawasaki KBB: Kawasaki Heavy Industries turbocharger product line including the KBB Kompressorenbau Bannewitz brand for medium-speed engines.
Kawasaki Steering Gear: Hydraulic rotary vane and ram steering gear actuators from Kawasaki Heavy Industries for large tankers and bulk carriers.
Kistler 6613: Kistler piezoresistive cylinder pressure transducer used for electronic indicator measurements on slow-speed diesels.

L

Lateral vibration: Whirling vibration of the shaft line, calculated to ensure adequate margin from running speed.
Light-running margin: Margin between MCR shaft speed and the propeller-curve intersection in the calm-water condition.
Liner inspection: Drift cover removal and visual check of cylinder liner condition.
Lloyd's Register PMS: Planned maintenance system approved by Lloyd's Register substituting continuous machinery survey items based on hours-run records.
LSFO (Low Sulfur Fuel Oil): 0.50% sulfur compliant residual fuel; similar GHG intensity to HFO.
Lube Oil Centrifuge: Alfa Laval or Mitsubishi separator removing water, sludge, and particulates from main engine system oil and fuel oil.

M

Mainbearing Survey: Inspection of two-stroke main bearings every 16,000 to 24,000 hours including white-metal examination and clearance measurement.
MaK 6M32: Caterpillar MaK 320 mm bore six-cylinder in-line medium-speed engine for marine main propulsion and large auxiliary duty.
MaK 9M32C: MaK medium-speed marine main engine with nine inline cylinders and 320 millimeter bore.
MAN 32/40 DF: Dual-fuel variant of the MAN 32/40 four-stroke engine capable of natural gas and diesel operation.
MAN 32/44CR: Four-stroke common-rail diesel engine.
MAN 45/60 CR: MAN Energy Solutions 450 mm bore common-rail medium-speed engine for cruise ship and large auxiliary applications.
MAN 48/60: 480 mm bore four-stroke marine engine from MAN Energy Solutions for large main and auxiliary duty.
MAN 51/60 DF: MAN Energy Solutions 510 mm bore dual-fuel medium-speed engine for LNG and oil operation.
MAN Alpha Adaptive Cylinder Oil Control: ACC system on MAN ME-C engines that adjusts cylinder oil feed rate proportionally to fuel sulfur and engine load.
MAN B&W G80ME-C: Ultra long stroke electronically controlled two stroke engine.
MAN B&W K98ME-C: 980 mm bore short-stroke high-power ME-C engine for large container ships.
MAN B&W S60ME-C: Two-stroke 60 cm bore electronically controlled engine.
MAN B&W S65ME-C: 650 mm bore long-stroke ME-C engine for VLCC main propulsion and Capesize bulkers.
MAN B&W S70ME-C: Electronically controlled super long stroke two stroke engine.
MAN B&W S90ME-C: 900 mm bore Super Long Stroke ME-C engine for VLCC and Capesize bulker propulsion.
MAN Holeby L16/24: MAN Energy Solutions 160 mm bore high-speed auxiliary genset engine for ships of moderate auxiliary load.
MAN Holeby L23/30H: MAN Energy Solutions 225 mm bore four-stroke auxiliary engine widely used as marine genset prime mover.
MAN Holeby L27/38: MAN Energy Solutions 270 mm bore four-stroke marine auxiliary and small main propulsion engine.
MAN Holeby L32/40: MAN Energy Solutions 320 mm bore four-stroke marine engine for auxiliary and main propulsion duty.
MAN Holeby V28/32S: Vee configuration auxiliary engine in the Holeby range used for marine genset applications.
MAN MC/MC-C: MAN B&W mechanically controlled two-stroke engine generation preceding the ME series, with camshaft-driven fuel pumps and exhaust valves.
MAN ME-B: MAN Energy Solutions electronically controlled two-stroke engine variant using mechanical fuel pumps and an electronic exhaust valve, served by Alpha Lubricator.
MAN ME-C: Fully electronically controlled MAN Energy Solutions two-stroke engine equipped with Alpha Lubricator cylinder oil injection.
MAN ME-GI: Two-stroke high-pressure (around 300 bar) gas-injection diesel engine by MAN Energy Solutions, Diesel cycle.
MAN ME-LGI: MAN dual-fuel ME engine designed for liquid gas injection of methanol, LPG, or ammonia using high-pressure pump and pilot oil ignition.
MAN NA Turbocharger: MAN classic axial turbocharger series superseded by the TCA generation.
MAN PrimeServ: After-sales service organization.
MAN TCA Turbocharger: MAN Energy Solutions axial-flow turbocharger family for large two-stroke engines, with bearing renewal at 16,000 to 24,000 hours.
MAN TCR Turbocharger: MAN Energy Solutions radial-flow turbocharger family for medium-speed engines.
MCR Maximum Continuous Rating: Engine power at which it can be operated continuously without time limit, the reference output for design and survey purposes.
Mean Effective Pressure mep: Indicator-diagram-derived average cylinder pressure used to calculate indicated power per cylinder.
Mechanical Efficiency etaM: Ratio of brake power to indicated power, typically 0.88 to 0.93 for large two-stroke engines and 0.85 to 0.90 for medium-speed.
MEPC Tier II: IMO MEPC NOx emission standard applicable to engines installed on or after 1 January 2011.
MEPC Tier III: IMO MEPC NOx emission standard applicable in designated ECAs, met by SCR, EGR, or dual-fuel operation.
MET-MA Turbocharger: Mitsubishi Heavy Industries axial-flow turbocharger first-generation for large two-stroke engines.
MET-MB Turbocharger: Mitsubishi MET second-generation axial turbocharger with hybrid bearings and improved efficiency.
Micro-Seizure: Microscopic adhesive wear between piston ring and liner surfaces causing vertical scuff marks and accelerated wear.
MissionSky Boiler: Aalborg auxiliary steam boiler with steam atomization burner used on dual-fuel and LNG-ready ships.
Mitsubishi Steering Gear: Mitsubishi Heavy Industries hydraulic ram and rotary vane steering gear for large merchant ships.

N

NCR Normal Continuous Rating: Operating power level for sea-going service equivalent to CSR, typically 85 percent of MCR.
Niigata 6L26HX: Niigata Power Systems 260 mm bore medium-speed four-stroke marine engine used as auxiliary and small main propulsion.
Nimonic 80A: Nickel-chromium alloy commonly used for exhaust valve spindles in two-stroke marine engines due to high-temperature fatigue strength.
Nitrite Inhibitor: Sodium nitrite added to closed-loop jacket cooling water to prevent ferrous corrosion, dosed to 1,000 to 2,400 ppm.
Non-Follow-Up Steering: Steering gear jog control mode where the rudder moves only while the helm is held, used in emergencies and harbour piloting.
Nozzle ring: Stator vanes directing exhaust onto turbocharger turbine wheel.

O

OEM (Original Equipment Manufacturer): Supplier of OT systems whose role under IACS UR E27 includes secure development and maintenance.
Oil mist detector: OMD continuously monitoring crankcase atmosphere, types include Schaller Visatron VN 116/87 and Specronix.
Oilon Burner: Finnish steam atomising burner used on Aalborg and Mission boilers, with annual nozzle and atomiser inspection.
Ovality: Cylinder liner or journal out-of-roundness measured by micrometer in two perpendicular planes during inspections.
Overhaul Interval: OEM-specified running-hour period between scheduled inspections, varying with engine type, fuel quality, and load profile.

P

Particle Count: Lube oil cleanliness measurement per ISO 4406 reporting particles greater than 4, 6, and 14 micrometres per millilitre.
Pcomp Compression Pressure: Cylinder pressure at TDC without combustion, used to diagnose ring wear and exhaust valve seat leakage.
PCV Pulse Lubricator: Hans Jensen pulse lubrication system delivering cylinder oil during a defined swirl-charged crank angle for optimal liner coverage.
Petromin: Saudi lubricants manufacturer with marine product lines for regional shipping.
Pielstick PC Series: Pielstick (now MAN Holeby) medium-speed engine series including PC2.6 and PC4.2 used on naval and merchant vessels.
Piston Crown: Combustion-side piston component manufactured from forged steel or Nimonic, examined for burn-through and crack initiation at piston pulls.
Piston Pull: Removal of the complete piston, rod, and crosshead assembly through the cylinder head opening, performed every 16,000 hours on MAN B&W two-strokes.
Piston Ring Renewal: Replacement of all compression and oil control rings at piston overhaul, with groove clearance measurement and CPR ring orientation.
Plummer Block: Intermediate shaft bearing housing in the shaft line, inspected for white-metal condition and oil-ring lubrication.
Pmax Peak Cylinder Pressure: Maximum combustion pressure recorded from the indicator diagram, key parameter for performance balance and component loading.
PMS Planned Maintenance System: Class-approved electronic maintenance regime tracking running hours and overhauls per OEM intervals.
PoroCheck: MacGregor rudder bearing wear-down measurement system used during dry-dock inspections.
Pressure Indicator Card: Mechanical or electronic recording of cylinder pressure vs. piston position for combustion analysis.
Pruftechnik Vibxpert: Pruftechnik route-based vibration analyser used for medium-speed engine and pump trend monitoring.
Pscav Scavenge Air Pressure: Charge air pressure at the scavenge receiver, used with turbocharger speed to assess compressor performance.
Pulse Jet Cleaning: Boiler tube cleaning technique using compressed air or steam pulses to dislodge soot from fire-side surfaces.

Q

Quenching: Heat treatment step in steel manufacture; relevant because freshly quenched plate has different surface behavior under priming.

R

Rapson slide: Crosshead arrangement converting hydraulic ram travel into rudder rotation in ram type steering gear.
RCM Reliability-Centred Maintenance: Structured methodology developed by Nowlan and Heap for selecting appropriate maintenance tasks based on failure consequences.
Reference Conditions: ISO 3046 ambient temperature, pressure, and humidity at which engine performance is declared, typically 25 deg C and 1.0 bar.
Ring Groove Measurement: Verification of piston ring axial and radial clearances by feeler gauge and groove micrometre during overhauls.
Rotary vane steering gear: Compact steering gear with vanes inside a stator providing rudder torque.
Run-In Procedure: Controlled load increase regime after major overhaul allowing rings, liner, and bearings to bed in, typically defined by OEM hours-versus-load curves.

S

Saacke Burner: German oil and gas steam boiler burner widely fitted to marine auxiliary boilers, with annual head and atomiser service.
Scavenge Inspection: 750-hour visual inspection through cylinder liner scavenge ports for piston ring condition, oil film, and deposits.
Scavenge Receiver: Common manifold between turbocharger and cylinders supplying charge air, drained periodically for FAS examination.
SCR (Selective Catalytic Reduction): NOx abatement using ammonia or urea; integral to many ammonia and dual-fuel installations.
Scrape-Down Oil: Used cylinder oil collected from the piston rod stuffing box on two-stroke engines, sampled for iron and BN trending.
Sea Margin: A power or speed margin added to design predictions to allow for added resistance from typical service conditions such as fouling, wind, and waves.
SFOC (Specific Fuel Oil Consumption): Engine fuel consumption in g/kWh corrected to ISO conditions.
Shaft alignment: Engineering process aligning engine, gearbox, intermediate, and tail shaft bearings to acceptable loads and angles.
Shell Rapid Lubrication Analysis: Shell Marine LubeAnalyst service providing rapid turnaround used oil analysis with online portal reporting.
Silicon Si: Lube oil contamination element indicating ingress of airborne dust through intake filtration breaches.
SIP Swirl Injection Principle: Hans Jensen cylinder oil injection system distributing oil into scavenge air swirl for uniform liner coating.
Slow Steaming: Operating below design speed to save fuel and reduce emissions.
Sludge: Water, sediment, and cat fines discharged from purifiers, logged in Oil Record Book.
Sodium Na: Lube oil contamination element indicating seawater ingress, typically from cooler tube leaks or scavenge air water carry-over.
SOLAS II-1/29: Steering gear performance requirement of 35 to 30 deg in 28 seconds at maximum service draft.
Spanner Pop Boiler: Vertical cross-tube steam vessel boiler from Spanner Boilers Ltd used as small auxiliary on workboats and tugs.
Steering gear test: SOLAS V/26 requires test before departure including main, auxiliary, communications, indicators, emergency power, and rudder angle.
Sulphation: Lube oil additive depletion mechanism producing sulfate species that consume base reserve and increase TAN.
Sulzer RT-flex: Common-rail electronically controlled two-stroke engine.