Extended Operational and Trade Vocabulary

EGCS Scrubbers, SCR and Marine Air Emissions glossary

The exhaust-treatment vocabulary: scrubber absorber towers and washwater, acid wash and demister cleaning, activated-carbon polishing for PAHs, continuous emission monitoring, and the open- and closed-loop EGCS and SCR terms. Grounds each term in the scrubber or SCR system and the MARPOL Annex VI compliance it serves.

304 defined terms.

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

A

ABB UCEM-2000: Continuous emission monitoring system supplied by ABB for shipboard SO2 and CO2 measurement on EGCS-equipped vessels.
ABS Advisory on EGCS: American Bureau of Shipping guidance document covering scrubber installation, survey and compliance considerations.
Absorber Tower: Vertical column in a wet scrubber where exhaust gas contacts alkaline washwater for SO2 removal.
Acid Wash: Cleaning procedure that removes scale and sulfate deposits from scrubber packing, nozzles and demister surfaces.
Activated Carbon Polishing: Optional post-treatment stage in closed-loop washwater plants for removing residual polycyclic aromatic hydrocarbons.
AdBlue: Trademarked 32.5% urea solution functionally equivalent to AUS32, occasionally referenced for high-speed marine SCR applications.
Aft Funnel Installation: Retrofit scrubber arrangement placed in the existing uptake casing aft of the engine room.
Air Cooler Fouling: Soot and sulfate deposition on charge air coolers that can be aggravated by high-sulfur fuel operation.
Air Pollution Prevention Certificate: Common reference to the IAPP issued under MARPOL Annex VI for each ship of 400 GT and above.
Alfa Laval PureNOx: Water cleaning unit used with EGR systems to remove sulfates and soot before water reuse.
Alfa Laval PureNOx Prime: Enhanced washwater treatment variant offering reduced footprint and higher throughput.
Alfa Laval PureSOx: Hybrid exhaust gas cleaning system supplied by Alfa Laval for open-loop, closed-loop and combined operation.
Alfa Laval PureSOx Connect: Remote monitoring and analytics service for PureSOx scrubber fleets.
Alkaline reserve: Quantity of base additive remaining in a used cylinder oil that can still neutralize combustion acids, measured by Base Number.
Alkalinity Sensor: Inline instrument measuring washwater alkalinity used in closed-loop scrubber control loops.
Ammonia slip: Unburned NH3 emitted from engines and SCR systems, regulated for toxicity and N2O formation.
Ammonium Bisulfate: Sticky deposit formed when SCR ammonia reacts with residual SO3, fouling downstream heat exchangers.
Ammonium Sulfate Aerosol: Secondary particulate formed from SCR ammonia slip combining with sulfur oxides in the exhaust.
Anchorage Restriction: Local prohibition on open-loop scrubber discharge at certain port anchorages such as Fujairah outer roads.
Andritz Marine Scrubber: Wet scrubber product line from Andritz AG for marine SOx abatement and washwater treatment.
Annex VI: Regulations for the Prevention of Air Pollution from Ships.
Approval in Principle: Preliminary class confirmation that a novel concept design satisfies applicable rules in principle, issued by IACS societies.
AUS32: Aqueous urea solution at 32.5% concentration used as reductant in marine SCR systems.
AUS40: Aqueous urea solution at 40% concentration used in some marine SCR systems for compact dosing.
Automated Measuring System (AMS): Continuous instrumentation chain qualified for regulatory emission reporting on board ship.
Auxiliary Boiler Bypass: Stack arrangement allowing oil-fired boiler exhaust to bypass the scrubber when not required.
Auxiliary Engine Scrubber: Dedicated EGCS branch treating exhaust from generator sets in addition to or separately from the main engine.

B

Backflushing: Periodic reverse flow through demister candles or hydrocyclones to dislodge accumulated solids.
Baltic NECA: Nitrogen Oxide Emission Control Area covering the Baltic Sea, in force for Tier III compliance from 1 January 2021 for keels laid on or after that date.
Baseline Test: Reference emission measurement performed under defined conditions to characterize scrubber or SCR performance.
Belco EGC: Marine exhaust gas cleaning product line developed by Belco Technologies for shipboard SOx removal.
Black carbon (BC): Sooty particulate emission from marine diesel; deposition on ice accelerates melt.
Black Carbon Reduction: Subject of ongoing IMO MEPC discussions concerning Arctic shipping and fuel selection.
Bleed-off Stream: Continuous purge from closed-loop washwater that is processed and either discharged or stored.
Blended Fuel: Very low sulfur fuel oil produced by combining residual and distillate streams to meet the 0.50% sulfur cap.
Blow Down: Controlled depressurization of cargo or fuel gas piping to the vent mast or GCU.
Booster Fan: Induced-draft fan installed to overcome scrubber back-pressure losses.
Brine Treatment: Removal of accumulated salts and dissolved metals from closed-loop scrubber bleed-off.
British Standards EGCS Reference: National-level standards occasionally cited in EGCS test reports alongside IMO guidelines.
Bunker delivery note: BDN, document required under MARPOL Annex VI Regulation 18 listing fuel quantity and sulphur content.
Bypass Damper: Mechanical damper used to divert exhaust around the scrubber during start-up, faults or maintenance.
Bypass Stack: Parallel uptake routing exhaust to atmosphere without scrubber treatment when permitted.

C

California Ports Discharge Ban: State-level prohibition on EGCS washwater discharge in regulated California port waters.
Carbon Intensity Indicator (CII): Operational indicator under MARPOL Annex VI Chapter 4.
Caterpillar SCR: Selective catalytic reduction systems offered by Caterpillar Marine for high-speed engines.
Caustic Consumption: Quantity of sodium hydroxide required per unit fuel burned in closed-loop scrubber operation.
Caustic Soda: Sodium hydroxide solution, typically 50% strength, dosed into closed-loop scrubber washwater.
Caustic Storage Tank: Dedicated tank carrying NaOH for closed-loop scrubber dosing.
CEMS: Continuous Emission Monitoring System used to verify regulated pollutant concentrations in the exhaust.
Certified Value: Manufacturer-declared emission level for an engine recorded on its EIAPP certificate.
China Coastal DECA: Domestic Emission Control Area covering Chinese coastal waters with fuel sulfur restrictions.
China Inland Waters Ban: Prohibition on open-loop EGCS discharge in China inland and certain territorial waters.
Chloride Stress Corrosion: Degradation mechanism affecting stainless steel scrubber components exposed to seawater chloride.
Closed-loop scrubber: Exhaust gas cleaning system using a recirculated alkaline wash with onboard residue handling.
CO2/SO2 Ratio: Emission ratio used under MEPC.340(77) as an equivalent indicator of fuel sulfur compliance.
CO2/SO2 Ratio 13:1: Ratio limit equivalent to 1.50% fuel sulfur content.
CO2/SO2 Ratio 21.7:1: Ratio limit equivalent to 1.00% fuel sulfur content.
CO2/SO2 Ratio 4.3:1: Ratio limit equivalent to 3.00% and 3.50% fuel sulfur content.
CO2/SO2 Ratio 40:1: Ratio limit equivalent to 0.50% fuel sulfur content under the global cap.
Combined Cycle Constraint: Limitation arising when SCR back-pressure interacts with turbocharger matching.
Combustion Air Temperature: Engine parameter influencing NOx formation, monitored under Scheme A daily checks.
Common Rail Tier III: Modern fuel injection arrangement that supports low-NOx combustion alongside aftertreatment.
Compliance Fuel: Marine fuel that meets the prevailing MARPOL Annex VI sulfur limit without further treatment.
Compliance Plan: Document describing how a ship will meet sulfur and NOx limits across its trading pattern.
Continuous Monitoring: Ongoing observation of shipboard and shore systems to detect security events.
Couple Systems DryEGCS: Dry scrubber product using hydrated lime granulate developed by Couple Systems.
CR Ocean Engineering: Marine scrubber supplier known by the acronym CROE.
CROE: Common shorthand for CR Ocean Engineering scrubber systems.

D

Daily Parameter Check: Verification of fuel index, load, engine speed and other parameters required under Scheme A.
Damper Position Feedback: Sensor signal confirming bypass or divert valve position for safety interlocks.
DEC Marine ECS: Marine exhaust cleaning system product line associated with EcoSpray Technologies.
DECA: Domestic Emission Control Area, primarily used to refer to Chinese coastal sulfur control zones.
Deck Discharge Connection: Standardized international shore connection for offloading sludge or spent washwater.
Deck Tank Sounding: Routine measurement of caustic, urea or sludge tank levels associated with EGCS operations.
Deep U-type Scrubber: Inverted U arrangement with extended absorber leg for increased gas-liquid contact.
DEF: Diesel Exhaust Fluid, a US designation for urea-water solution used in SCR systems.
Delft Exhaust Cleaning: Reference to early Dutch development of marine EGCS technology in the Netherlands.
Demineralized Water: Treated water used as makeup in closed-loop scrubbers to limit scale formation.
Demister: Internal device that removes entrained droplets from the scrubber exit gas.
Direct Measurement Method: Sulfur compliance verification through onboard SO2/CO2 measurement.
Divert Valve: High-temperature valve directing exhaust to scrubber or bypass paths.
Dosing Pump: Metering pump delivering caustic or urea at a controlled rate.
Double Bottom Caustic Tank: Structural tank arrangement carrying NaOH below the lower deck.
Dry EGCS: Exhaust gas cleaning technology using solid hydrated lime granulate instead of washwater.
Dry Scrubber: Synonym for dry EGCS, removing SOx through reaction with calcium hydroxide.
Duct Burner: Auxiliary burner used in some SCR arrangements to maintain catalyst inlet temperature.

E

EAL: Environmentally Acceptable Lubricant qualifying for use in oil-to-sea interfaces of vessels subject to the US Vessel General Permit and Vessel Incidental Discharge Act.
EcoSpray Technologies: Italian supplier of marine wet scrubbers and washwater treatment plants.
EEDI: Energy Efficiency Design Index, MARPOL Annex VI Chapter 4.
EEXI: Energy Efficiency Existing Ship Index, MARPOL Annex VI Chapter 4.
EGCS: Exhaust Gas Cleaning System, the IMO term for marine SOx scrubbers.
EGCS Discharge Criteria: Washwater limits for pH, PAH, turbidity and nitrate under MEPC.340(77).
EGCS Guidelines: IMO instruments setting out approval and operational requirements for marine scrubbers.
EGCS Record Book: Onboard log of scrubber operational data, sludge handling and washwater monitoring.
EGCS Scheme A: Unit certification route plus daily parameter checks for sulfur compliance.
EGCS Scheme B: Continuous SO2/CO2 emission monitoring route with parameter verification.
EGR: Exhaust Gas Recirculation, an in-engine NOx control technique alternative to SCR.
EGR Bleed-off: Treated liquid stream from MAN EGR water mist catcher requiring onboard processing.
EIAPP Certificate: Engine International Air Pollution Prevention certificate issued under NOx Technical Code.
Emission Abatement Method: Generic Annex VI term for equivalent technologies achieving sulfur or NOx compliance.
Emission Control Area (ECA): Sea area with stricter SOx, NOx, or PM controls.
End-of-Pipe: Treatment approach acting on the exhaust after combustion rather than in the engine.
ENVI-Marine: Pacific Green Marine Technologies brand for its seawater scrubber system.
Equivalent Means: Approval pathway allowing alternative technologies to meet Annex VI requirements.
ETS Maritime: Inclusion of shipping in the EU Emissions Trading System covering CO2 emissions.
EU ETS Phase-in: 40% of emissions surrendered for 2024, 70% for 2025, 100% from 2026 for in-scope ships.
EU MRV: EU Regulation 2015/757 on monitoring, reporting, and verification of CO2 emissions from shipping.
Exhaust Bypass: Permanent or temporary arrangement to route gas around the EGCS.
Exhaust Gas Bypass Valve: Stainless steel high-temperature valve isolating or admitting gas to the scrubber.
Exhaust Gas Recirculation Cooler: Heat exchanger that cools recirculated exhaust before mixing with charge air.
Exhaust Gas Sampling Probe: Heated probe in the stack feeding analyzers for SO2, CO2 and NOx.

F

Feed pump: Boiler feed pump delivering water from hotwell to the boiler drum.
Fishing-eye Nozzle: Spray nozzle profile used in some scrubber designs to achieve fine droplet distribution.
Flag State Approval: Authorization required by IMO MSC.1/Circ.1406 before PCASP may embark.
Flexible coupling: Resilient torsional or torsionally rigid coupling joining engine and gearbox or gearbox and shaft.
Flue Gas Desulfurization: Land-based parent technology from which marine EGCS designs derive.
Footprint: Geographic area covered by a satellite beam.
FRP Internals: Glass-fiber-reinforced plastic packing and trays used in some marine scrubbers.
Fuel Oil Change-over Procedure: Sequence followed when switching to compliant fuel ahead of ECA entry.
Fuel Oil Sample: MARPOL-delivered sample retained under Regulation 18.
Fuel Sulfur Content: Mass percentage of sulfur in marine fuel, regulated under MARPOL Annex VI.
FuelEU Maritime: European Union regulation imposing greenhouse gas intensity limits on shipping fuels, driving development of pooling mechanisms and compliance instruments.
Fujairah Anchorage Restriction: Local prohibition on open-loop discharge at the Fujairah outer port anchorage.

G

Gas Carrier SCR: SCR installation aboard LNG or LPG carriers, often integrated with dual-fuel propulsion.
GHG Intensity: Well-to-wake greenhouse gas emission intensity used in FuelEU Maritime accounting.
Global Sulfur Cap: 0.50% fuel sulfur limit in force outside ECAs from 1 January 2020.
Goeree Marine: Dutch supplier historically associated with marine exhaust gas cleaning equipment.
GRE Pipework: Glass-reinforced epoxy piping commonly specified for scrubber washwater service.
Great Lakes EGCS Restrictions: US Great Lakes prohibitions on certain scrubber discharges.

H

H+H Engineering: Supplier associated with SCR system engineering for medium-speed marine engines.
Halocarbons: Refrigerant gases regulated separately under MARPOL Annex VI Reg 12.
Hamworthy Krystallon: Predecessor brand acquired into Wartsila Exhaust Gas Cleaning portfolio.
Hawaii Port Discharge Restrictions: State-level restrictions on EGCS washwater discharge in Hawaiian waters.
Heat Exchanger Plate Cooler: Component cooling recirculated washwater in closed-loop scrubber loops.
High Sulfur Fuel Oil (HSFO): Residual fuel typically at 3.5% sulfur historically used with scrubbers.
Hitachi Zosen Inova SCR: Marine selective catalytic reduction system from Hitachi Zosen.
Holding tank: shoreside tank for sewage or ballast reception.
HSFO: High sulfur fuel oil with sulfur content above 0.5 percent, permitted on ships fitted with compliant exhaust gas cleaning systems.
Hybrid Scrubber: EGCS capable of switching between open-loop and closed-loop modes.
Hydrated Lime: Calcium hydroxide granulate used as reagent in dry scrubbers such as Couple Systems DryEGCS.
Hydrocyclone: Centrifugal device removing solid particles from scrubber washwater.
Hydrolysis Catalyst: Reactor converting urea into ammonia upstream of SCR catalyst beds.

I

I-type Scrubber: Vertical inline scrubber arrangement with straight gas path.
IAPP Certificate: International Air Pollution Prevention Certificate under MARPOL Annex VI.
ICE Engine Tier: Internal combustion engine NOx tier classification under MARPOL Annex VI Reg 13.
IMO Initial GHG Strategy: 2018 IMO strategy setting first targets for shipping greenhouse gas emissions.
IMO MEPC: Marine Environment Protection Committee setting environmental rules.
IMO Revised GHG Strategy: 2023 IMO strategy targeting net-zero emissions from international shipping around 2050.
In-line SCR: SCR reactor mounted directly in the exhaust line between engine and silencer.
Independent Verification: Class or recognized organization survey of EGCS continuous emission monitoring data.
Indirect SCR: SCR arranged with separate mixing duct and reductant injection ahead of the catalyst.
Inland Waterway Restrictions: Bans on open-loop EGCS discharge in selected inland waterways such as German rivers.
Inlet Cone: Diverging section distributing exhaust evenly across the scrubber cross-section.
Inlet Quench: Initial water spray cooling exhaust gas at scrubber inlet to operating temperature.
Inspection Hatch: Maintenance access on scrubber towers, demisters and sumps.
Integrated Bilge Treatment: Some EGCS designs share treatment skids with oily bilge processing.
Interlock Logic: Safety logic preventing scrubber operation outside permitted envelope.
Intermediate Fuel Oil (IFO): Older trade term for residual blends 180 and 380 cSt.
ISO 8217: International standard for marine fuel oil specifications.

J

Jet Scrubber: Wet scrubber configuration using high-velocity liquid jets to entrain and clean exhaust gas.

K

Kawasaki Marine SCR: Reference to SCR designs delivered for Kawasaki two-stroke and four-stroke engines.
Keel-laying Date: Reference date used to determine applicable NOx Tier under MARPOL Annex VI.
Krystallon Hybrid: Early hybrid EGCS design developed by Krystallon prior to Wartsila acquisition.

L

Lime Silo: Pressurized vessel storing hydrated lime granulate for dry scrubber dosing.
LNG Dual-fuel: Engine technology offering an alternative compliance pathway to scrubbers and SCR.
Local Discharge Ban: Port or coastal restriction on open-loop EGCS washwater discharge.
Low Pressure SCR: SCR reactor located downstream of the turbocharger for two-stroke engines.
Low sulfur marine gas oil (LSMGO): Marine gas oil with sulfur content at or below 0.10 percent for SECA compliance.

M

MAN B&W EGR: MAN Energy Solutions exhaust gas recirculation system for two-stroke engines.
MAN Energy Solutions SCR: SCR retrofit and newbuild solution for MAN two-stroke and four-stroke engines.
MAN SCR-HP: High-pressure SCR variant for MAN engines positioned upstream of the turbine.
MAN SCR-LP: Low-pressure SCR variant for MAN engines positioned downstream of the turbine.
Marine Exhaust Solutions (MES): Canadian supplier historically associated with EcoSilencer marine scrubber.
MARPOL Annex VI: Air pollution and energy-efficiency annex.
MARPOL Annex VI Reg 13: Regulation governing NOx emissions and Tier I/II/III thresholds.
MARPOL Annex VI Reg 14: Sulphur content of fuel oil global cap (0.50% m/m) and ECA cap (0.10% m/m).
Mediterranean SECA: Sulfur Emission Control Area covering the Mediterranean Sea, in force from 1 May 2025.
MEPC.184(59): IMO Marine Environment Protection Committee resolution setting the 2009 Guidelines for exhaust gas cleaning systems, complementary to bunker quality controls.
MEPC.259(68): 2015 IMO EGCS guidelines superseding MEPC.184(59).
MEPC.340(77): 2021 IMO EGCS Guidelines currently in force.
MEPC.346(78): 2022 IMO resolution related to Annex VI implementation.
Methanol Dual-fuel: Engine technology offering an alternative low-SOx compliance pathway.
MGO: Marine gas oil, distillate fuel per ISO 8217 DMA.
Mist Eliminator: Device removing fine droplets from scrubber exit gas, often a vane pack or candle filter.
Mitsubishi Hitachi Power Systems: Supplier active in large land-based and marine SCR catalysts.
Mitsubishi MHI-MET SCR: Marine SCR system from Mitsubishi Heavy Industries Marine Engineering & Technology.
Mixing Duct: Section between urea injection and SCR catalyst promoting reductant distribution.
Multi-stream Scrubber: Single scrubber tower treating exhaust from multiple engines in parallel.

N

NaOH Storage: Caustic soda storage tank associated with closed-loop scrubber operation.
NECA: Nitrogen Oxide Emission Control Area where Tier III applies to qualifying new ships.
Net-zero Pathway: Concept embedded in the 2023 IMO Revised GHG Strategy.
Neutralization Tank: Closed-loop scrubber tank where acidic washwater is neutralized before further treatment.
NH3 Slip: Synonym for ammonia slip from SCR systems.
Nitrate Discharge Limit: Washwater discharge requirement for nitrate under MEPC.340(77).
Nitric Oxide (NO): Primary NOx species formed during combustion.
Nitrogen Dioxide (NO2): Secondary NOx species formed by oxidation of NO in the exhaust.
Nitrous Oxide (N2O): Greenhouse gas occasionally formed in low-temperature SCR operation.
Norway World Heritage Fjords: Specific Norwegian fjords subject to strict emission and discharge restrictions.
NOx Reducer: Wartsila trade name for its marine SCR system.
NOx Technical Code 2008: Mandatory under MARPOL Annex VI.
NOx Tier I: Applicable to engines on ships with keels laid on or after 1 January 2000 and before 1 January 2011.
NOx Tier II: Applicable to engines on ships with keels laid on or after 1 January 2011, globally.
NOx Tier III: MARPOL Annex VI NOx limit applying in NOx ECAs; relevant for SCR-equipped alt-fuel engines.
NOxReducer Yara: Yara Marine Technologies SCR product line for marine engines.

O

Off-spec Fuel: Marine fuel found not to meet declared sulfur content on testing.
Onboard Sulfur Compliance Verification: Testing of in-use samples for fuel sulfur content.
Open loop scrubber: Exhaust gas cleaning system using once through sea water under MEPC.340(77).
Open-loop Ban: Local prohibition on open-loop scrubber discharge in certain ports and coastal waters.
Operating Window: Range of engine load and ambient conditions within which an EGCS or SCR is certified.
Outlet pH: Discharge water pH measured at the overboard line, required to be 6.5 minimum at the discharge point.
Overboard Discharge Line: Pipe routing treated washwater to a single, identifiable hull penetration.
Overboard Monitoring System: Set of instruments measuring discharge water pH, PAH, turbidity and temperature.

P

Pacific Green Marine Technologies: Supplier of the ENVI-Marine scrubber product line.
Packed Bed Scrubber: Tower scrubber containing structured or random packing to maximize gas-liquid contact.
PAH Phenanthrene Equivalent: Polycyclic aromatic hydrocarbon discharge limit expressed in MEPC.340(77).
Panama Canal Lakes Restriction: Authority restriction on EGCS washwater discharge in Panama Canal lake waters.
Parameter Check: Daily verification of engine operating parameters under Scheme A EGCS compliance.
Particulate matter (PM): Solids emitted in exhaust, influenced by fuel ash and residue.
Pellet Bed: Hydrated lime granulate bed in a dry scrubber providing the reaction surface for SOx absorption.
PEMS: Portable Emissions Monitoring System used for in-service or survey testing.
Pentapod Structure: Steel support structure built around a scrubber tower for stability in funnel installations.
pH 6.5 Discharge Criterion: Minimum overboard washwater pH at the discharge point per EGCS Guidelines.
pH Probe: Glass or solid-state electrode measuring washwater acidity at scrubber discharge.
Phenanthrene Equivalent: PAH metric used in scrubber washwater discharge criteria.
Plate Heat Exchanger: Heat exchanger using stacked plates with gaskets for compact heat transfer.
Polishing Bed: Optional charcoal or zeolite bed for residual organic removal from scrubber bleed-off.
Portable Sulfur Analyzer: Handheld instrument used for sulfur compliance verification of fuel samples.
Pre-scrubber: Initial wet stage cooling and roughing the exhaust ahead of the main absorber.
Pre-treatment: Preparatory exhaust handling such as soot reduction ahead of SCR catalyst.
Pressure Drop: Exhaust back-pressure increase imposed by scrubber or SCR equipment.
PureNOx Prime: Compact washwater cleaning unit from Alfa Laval for closed-loop bleed-off.
PureSOx: Alfa Laval scrubber product line covering open-loop, closed-loop and hybrid configurations.

Q

Quench Section: Initial cooling stage immediately downstream of exhaust entry into a wet scrubber.

R

Recirculation Pump: Pump moving washwater between scrubber sump and spray headers in closed-loop operation.
Record Book of Engine Parameters: ONboard log required by NOx Technical Code for certified engines.
Reductant: General term for the urea or ammonia agent dosed into an SCR system.
Reductant Dosing Unit: Skid metering urea solution to SCR injection lances.
Reductant Storage Tank: Insulated and heated tank carrying AUS40 or equivalent urea solution.
Residue Separator: Equipment isolating sludge from scrubber washwater for storage and disposal.
Reverse Jet Scrubber: Scrubber design in which liquid is injected against the gas flow for intensive contact.

S

Saacke Marine: German supplier of marine burners and electrical control systems for boilers and steam plants.
Sampling Frequency: Frequency of EGCS performance and washwater sampling required for verification.
Scheme A: Certification scheme combining unit type approval and parameter check for EGCS sulfur compliance.
Scheme B: Certification scheme based on continuous SO2/CO2 monitoring of EGCS exhaust.
SCR: SAR Cooperation Plan required under SOLAS Chapter V Regulation 7.3 for passenger ships.
SCR-HP: High-pressure SCR for two-stroke engines mounted upstream of the turbocharger.
SCR-LP: Low-pressure SCR for two-stroke engines mounted downstream of the turbocharger.
SCR-N: Wartsila SCR variant for NOx reduction on its medium-speed engines.
SCR-S: Wartsila SCR variant for specific engine series and exhaust temperature ranges.
Seawater Alkalinity: Buffering capacity of ambient seawater used in open-loop scrubbers.