Marine exhaust gas cleaning spare parts — a sourcing guide for scrubbers and SCR under IMO 2020, EU ETS and Tier III NOx rules

EGCS (scrubber) OEM families — open-loop, closed-loop, hybrid

EGCS product lines may use open-loop, closed-loop or hybrid arrangements, but not every maker or model supports every mode. The mode decides the spares population. An open-loop system neutralises with the natural alkalinity of seawater, so it is built around large-flow seawater pumps and the tower internals. A closed-loop system recirculates fresh water dosed with caustic soda, which adds a dosing skid, a buffer tank, a cooler to reject the heat that seawater used to carry away, bleed-off treatment and sludge handling, and the wetted parts downstream of the dosing point are chosen for caustic and not for seawater. A hybrid holds both. Confirm the installed system and its approved configuration from the nameplate and technical documentation (Alfa Laval technical overview).

• Wärtsilä Exhaust Treatment (formerly Hamworthy Krystallon) — Open Loop (OL), Closed Loop (CL) and Hybrid (HS) systems delivered as the conventional quench/venturi EGCU Scrubber or the compact Inline Scrubber, plus the newer, lighter-weight IQ Series for container vessels. Wärtsilä also markets V-SOx (venturi-inlet, also supplied as a hybrid that runs in open or closed loop) and Q-SOX designs within the same family. A tower delivered before Wärtsilä took over Hamworthy in 2012 may carry a Hamworthy or Krystallon plate, and Wärtsilä's own Hamworthy product list still shows exhaust gas cleaning. Before the RFQ names a maker, check the Hamworthy page, which sets out which business now holds each former Hamworthy line (Wärtsilä Exhaust Treatment equipment page; International Filtration News on the IQ Series).
• Alfa Laval PureSOx — three compliance profiles: PureSOx Global (0.5% S, smallest footprint), PureSOx ECA (the original design, for 0.1% S ECA compliance), and PureSOx Flex (switchable), each configurable as open-loop, closed-loop or hybrid, in U-design (side inlet) or inline I-design (Alfa Laval PureSOx product brochure).
• Yara Marine Technologies — open-loop, closed-loop and hybrid arrangements documented across its project history (Yara project release).
• CR Ocean Engineering (CROE) — Open Loop, Closed Loop, and Hybrid designs, further differentiated into In-line (bottom inlet), Off-line (side inlet), and U-line configurations, plus a High Energy Venturi inlet option for fine-particle capture and a Caustic Assist™ Open Loop variant (CR Ocean Engineering; US MARAD Scrubber Selection Guide). CROE has an equipment partnership with Oberlin Filter for closed-loop/hybrid washwater filtration (Maritime Executive on the CROE–Oberlin partnership).
• Fuji Electric (SaveBlue) — cyclone-type SOx scrubber marketed by engine-capacity class: S, M, L, 2L and XL, available in open-loop and hybrid types; the class letter is what appears on the system plate and in the parts book, so quote it rather than an engine output (Fuji Electric EGCS solution page).
• Panasia (PaSOx) — wet scrubber line spanning the U-Type, I-Type, Square Type and Micro Type product classes, the Micro Type covering the smallest installations; quote the type name and the system model from the plate rather than an engine output (Panasia scrubber product page).
• DuPont Marine Scrubbers (BELCO) — marine scrubbers built by Belco Technologies Corporation (BELCO), then a DuPont subsidiary, in hybrid, open-loop and closed-loop configurations and mechanically designed for the full exhaust gas temperature (Maritime Executive on a DuPont/Vulica retrofit order). Note: on 31 December 2021 DuPont sold its Clean Technologies business, BELCO scrubbing technology included, to a private-equity consortium. The business now trades as Elessent Clean Technologies, and its current BELCO pages describe refinery and industrial gas cleaning, not marine units. A plate reading DuPont or BELCO therefore does not show who supports the unit today, so send the plate photo and the commissioning documents with the RFQ.

SCR OEM families for NOx compliance

Selective Catalytic Reduction (SCR) systems inject a urea solution into the exhaust stream upstream of a vanadium-titanium catalyst to reduce NOx to N2 and H2O, and are the primary secondary abatement method for IMO Tier III compliance (ICCT Tier III technology review).

• Wärtsilä NOx Reducer (NOR) — fully integrated with Wärtsilä's four-stroke medium-speed engine range for newbuild and retrofit (Wärtsilä NOR product page). For low-speed two-stroke engines, Wärtsilä/WinGD have deployed pre-turbocharger High-Pressure SCR (HP SCR). The first such engine produced in China, introduced in January 2015, was a five-cylinder RT-flex58T-D, an engine family covered on the Sulzer RT-flex page (WinGD/Wärtsilä two-stroke HP SCR news).
• Everllence / legacy MAN Energy Solutions — MAN SCR and MAN SCR-HP families for four-stroke and two-stroke applications (technology brochure), including the Cluster 5 Double Layer SCR project supplied to MITSUI E&S (project release).
• Hitachi Zosen (Kanadevia) — Hitz Green SCR — the Mk-II marine SCR, developed since 2009 with MAN Energy Solutions as engine licensor, takes high-temperature, high-pressure exhaust gas upstream of the turbocharger on two-stroke engines and is offered for MAN B&W and WinGD types. Kanadevia's marine engine business passed to Hitachi Zosen Marine Engine Co., Ltd. on 1 April 2023, while SCR parts sales are still listed under the after-sales section of Kanadevia's site, so check which company the plate and the service letters name (Kanadevia marine diesel SCR page).
• Panasia — PaNOx / PaNOx Marine — a dedicated PaNOx Marine variant engineered specifically to meet IMO Tier III standards (Panasia PaNOx product page).
• Kwangsan (Kwang San Co., Ltd.) — the Komachine marketplace listing cited here, posted in 2017, belongs to Kwangsan, not to Kwangsung, and offers a modular SCR in Class 1 to Class 11 sizes (Komachine SCR system listing). Kwangsan's own product pages currently list air vent heads, expansion joints, pipe spools, heating coils and plant projects, with no SCR among them, so identify a unit from this source by its plate and the maker's documentation rather than from a catalogue.

Scrubber wear parts — pumps, nozzles, effluent sensors

Every wetted part in this plant lives in an acidic, chloride-bearing wash, so on a scrubber the alloy is the specification. The scrubber unit and the pumps, coolers, pipework and valves downstream of it are built in super-duplex or super-austenitic stainless steels with a pitting resistance equivalent number (PREN) above 40, in titanium, or in non-metallics such as glass-reinforced epoxy pipe. The 304 and 316L found elsewhere on board sit at about PREN 20 and 25, which is too low for this duty: a part of the right dimensions in ordinary 316 will fit and will then pit, so state the grade from the material certificate and not from the look of the part. Recurring scrubber RFQ categories include mechanical and instrumentation components inside the tower and circulation loop:

• Sea-water pumps (open-loop) — high-flow centrifugal pumps whose duty point, material, seal and motor rating must match the approved system design. DESMI, for example, builds its NSL, DSL and ESL scrubber pumps as vertical in-line centrifugal pumps in either nickel-aluminium bronze or super-duplex stainless steel, and calls super duplex by far the best choice for its NSL pumps where the pumped liquid is aggressive or polluted. Quote the pump type and material exactly as the pump plate gives them, and take the duty point from the system documentation rather than from a guideline figure (DESMI Scrubber Pumps brochure).
• Circulation pumps (closed-loop) with caustic dosing — lower-flow recirculation pumps paired with a NaOH (caustic soda, typically 40–60% solution) dosing skid, buffer tank with fresh-water make-up, and a water treatment plant with sludge collection (Alfa Laval "Understanding exhaust gas treatment systems").
• Spray nozzles and packing media — wetted internals inside the scrubber tower; classical designs include bubble plate, cyclonic, packed bed, and spray tower configurations. Nozzles wear from the inside: the orifice opens, so flow rises at the same pump pressure while the spray angle and droplet size drift and coverage falls. A nozzle that looks sound can be well outside its flow tolerance, and it is ordered by flow number, spray angle, connection and material. The demister at the tower outlet fails the other way, by fouling and by collapse of the pack; its differential pressure is the indicator, and carryover past a tired demister shows as deposits and corrosion in the uptake (EGCSA Handbook 2012).
• pH, PAH and turbidity sensors — match the sensor, measurement range, method, calibration and data interface to the vessel's approved monitoring arrangement and applicable MEPC.340(77) requirements. MEPC.340(77) ties the PAH measuring principle to the washwater flow rate the system was approved at, accepting ultraviolet measurement only at the lowest flow rates and requiring fluorescence above them. It also judges turbidity as the difference between inlet and discharge water, so both measuring points belong to the approved arrangement. Maintenance of these instruments, like-for-like replacements included, is entered in the EGCS Record Book. These instruments are compliance items rather than accessories: the make, measurement principle and range are written into the approved documentation. A replacement of a different type is a change to the approved arrangement and not a like-for-like swap, and a sensor that arrives without its calibration certificate and the right interface to the recording unit is unusable for compliance (technical overview of MEPC.340(77) monitoring).
• Wash-water treatment (hydrocyclones, filtration) — closed-loop bleed-off streams are processed through hydrocyclone separators and/or automatic filtration before discharge or sludge storage (Maritime Executive on the CROE–Oberlin partnership).

SCR wear parts — catalyst, dosing, sensors

A scrubber is wet, cool and acidic; an SCR is dry and hot, and its real constraint is a temperature window. Below that window, sulphur in the fuel forms ammonium bisulphate which fouls and plugs the catalyst, so low-load running and the reactor bypass matter here more than any wear part; above it the catalyst ages thermally. SCR reactors have their own recurring wear-part categories, distinct from scrubbers:

• SCR catalyst blocks — catalyst chemistry, cell form and operating window vary by engine, fuel, reactor design and approval basis. Match replacement elements to the approved engine and catalyst specification rather than applying a generic chemistry or temperature range. Catalyst is lost in three ways. Soot fouls it, and soot blowing removes that. Ammonium sulphate and bisulphate plug its pores when the exhaust runs too cool on sulphur-bearing fuel. Sodium, potassium, calcium, magnesium, phosphorus and zinc compounds from fuel and lubricating oil poison it. Its life is therefore judged by NOx conversion and ammonia slip rather than counted in hours, and a rising urea feed for the same NOx reduction is the early warning. Elements are commonly renewed a layer at a time, which makes the order a question of how many layers, at what cell pitch, in which frame. Under the IMO SCR guidelines the block specification and arrangement are recorded in the engine's NOx Technical File, and a surveyor checks the part or specification number marked on the block casing or frame, so send that number (review of vanadium SCR catalysts).
• Urea/AdBlue dosing pumps and nozzles — a reagent pumping unit, dosing unit, mixing unit, and injection nozzle set upstream of the catalyst reactor. Marine systems are commonly dosed with a 40 per cent aqueous urea solution rather than the 32.5 per cent road-grade fluid, and the dosing control is set for the concentration it was commissioned on. Urea attacks copper alloys, zinc and unprotected carbon steel, so the wetted parts on this side are stainless or specified polymers. The failures that repeat are crystallised deposits in the injector and the mixing duct (Wärtsilä NOx Reducer system overview).
• Urea tank heating — urea/AdBlue solutions can crystallize or freeze at low ambient temperatures, so tank and line heating/insulation is standard for vessels trading in cold-water regions.
• NOx sensors — marine SCR dosing is typically set from engine load and speed, and on some systems NOx and ammonia measurement feeds back to trim the dosing and record performance. On those systems the analyser is part of the control loop, so quote its make and type from the SCR control documentation rather than ordering a generic NOx sensor.
• Reactor housing internals — catalyst support frame, soot-blowing/cleaning unit (Wärtsilä NOx Reducer system overview).

Class-society and regulatory context

EGCS guidance has evolved through MEPC.184(59), MEPC.259(68) (IMO resolution text) and MEPC.340(77) (IMO resolution text). The 2021 Guidelines in MEPC.340(77) apply to EGCS on ships whose keels were laid on or after 1 June 2022, to EGCS contracted for delivery, or delivered, to older ships on or after that date, and to amendments made to an existing EGCS from that date. An amendment in this sense is a change that affects emissions to air or water and needs the Administration's approval as an amendment to the EGCS Technical Manual, so a change of that kind made today brings an older installation under the 2021 Guidelines. Identify the guideline and approved ETM, OMM and compliance documents before requesting monitoring-system components. For SCR the matching references are resolution MEPC.291(71), as amended by MEPC.313(74). The engine's NOx Technical File records the reductant type and concentration, the injection arrangement and the catalyst block specification and arrangement, so these are approval items rather than free choices.

The Administration, itself or through a recognized organization acting on its behalf, approves the EGCS as an equivalent under regulation 4 of MARPOL Annex VI. Confirm the exact approval records—such as the SECC, SECP, ETM and OMM where applicable—rather than relying on a generic statement of compliance. The approval scheme also fixes how much weight sits on an instrument. Under Scheme A the unit itself is certified, holds an SECC and is verified on continuously monitored operating parameters against its certified range. Under Scheme B the approved exhaust gas monitoring system must show the Emission Ratio continuously, so the analyser itself has to be in service and calibrated. The SECP, ETM and OMM apply under either scheme; only Scheme A has an SECC. An RFQ therefore carries the system model and serial, the approval scheme and reference and the tag number from the system diagram. A P&I club jurisdiction list can provide background but is not the approval authority.

Discharge restrictions are mutable and may differ by port limits, coastal-state waters, canal rules, discharge mode and voyage conditions. One change already has dates. OSPAR Decision 2025/01 sets common rules for EGCS discharge water in the internal waters and port areas of the OSPAR states of the North-East Atlantic. Britannia P&I reports that it bans open-loop discharges there from July 2027 and closed-loop discharges from January 2029, and an extension to territorial seas is still under study. For spares this means that from 2027 a hybrid calling at those ports depends on its closed-loop side, and from 2029 on zero-discharge operation with a holding tank, so those are the parts of the plant that keep the scrubber usable there. Use the P&I jurisdiction list and the ICCT policy review only as background; before voyage planning, verify the current port, coastal-state and flag-state requirements and the vessel's approved procedures.

OEM route vs verified alternative

For nozzles and packing media, verify dimensions, materials, hydraulic duty and maker acceptance before considering a non-OEM option (CECO Environmental product reference). For pH, PAH, turbidity, CEMS and NOx instrumentation, the sensor, calibration, data logging and reporting interface must match the approved ETM or OMM and obtain any required maker, Administration or class acceptance (monitoring overview). Pump duty, material and seal must match the approved system design (DESMI Scrubber Pumps brochure). SCR catalyst elements must match the engine, fuel, reactor and NOx Technical File requirements; assess any substitution through the applicable approval process (technology brochure).

What we cannot promise before the RFQ is reviewed

Vessel Core sources exhaust-gas-cleaning and SCR spare parts; it does not issue class certification or regulatory approval, and it cannot certify that a vessel remains compliant once a part is fitted. Prices, lead times and supply route are not stated before the unit, approved arrangement, fuel in use and documentation context are confirmed. A quotation for sensors or catalyst elements remains preliminary until the applicable approval and technical-file references are available.

How to send the RFQ

Use the RFQ form. Attach the scrubber-tower or SCR-reactor nameplate photo, the OEM system model and serial number, the discharge system type (open-loop, closed-loop, or hybrid), and the current fuel type in use. Or use the RFQ evidence checklist to walk through the fields item by item.

Frequently asked questions

What EGCS scrubber OEM families does this guide cover?

The guide covers Wärtsilä Exhaust Treatment, Alfa Laval PureSOx, Yara Marine Technologies, CR Ocean Engineering, Fuji Electric SaveBlue, Panasia PaSOx and DuPont BELCO families. Available open-loop, closed-loop or hybrid arrangements vary by maker, product line and installation, so confirm the exact system model and approved configuration.

What SCR OEM families does this guide cover?

Wärtsilä NOx Reducer (NOR) and High-Pressure SCR for two-stroke engines, MAN SCR (14 sizes plus SCR-HP and the Cluster 5 catalytic converter), the Hitachi Zosen/Kanadevia Mk-II pre-turbocharger SCR, Panasia PaNOx Marine, and the modular Class 1-11 SCR listed by Kwangsan.

MEPC.340(77) vs MEPC.259(68) — which is current?

MEPC.340(77) contains the 2021 EGCS Guidelines and superseded MEPC.259(68), which had superseded MEPC.184(59). Applicability and the vessel's approved monitoring arrangement depend on its approval basis and documentation. Before an RFQ for sensors or monitoring components, identify the guideline and approved technical documents referenced by the installation.

Where should current scrubber-discharge restrictions be checked?

Restrictions change and can differ by port limits, coastal-state waters, canal rules, discharge mode and voyage conditions. Check the current port, coastal-state and flag-state requirements, the vessel's approved procedures and an up-to-date official or P&I notice before voyage planning. A dated summary should not be treated as operational authority.

What identity evidence does an EGCS or SCR RFQ need?

Send the OEM system model and serial number, the approved open-loop, closed-loop or hybrid arrangement, fuel in use, and the applicable approval documents. Depending on the installation, these may include the SECC, SECP, ETM, OMM, NOx Technical File or EIAPP documentation. Add relevant maintenance data such as pump hours, catalyst pressure-drop history and sensor calibration records.

Related reading

• Marine cooling water sourcing guide
• Marine fuel injection sourcing guide
• Marine pumps sourcing guide
• RFQ evidence guide
• RFQ case notes