Composite Boiler
medium
3 models total
A composite boiler combines an exhaust gas economiser section and an oil-fired furnace in a single pressure vessel, so the same steam drum makes steam from waste heat while under way and switches to oil firing in port or at low load.
Read more — Composite Boiler explained ▾
What makes a composite boiler different
A dedicated exhaust gas economiser only makes steam when the main engine is running hard enough to produce useful exhaust heat, and a separate oil-fired boiler is needed for port stays, manoeuvring and low-load steaming. A composite boiler puts both heat sources into one shell around a common steam drum: an exhaust gas tube bank sits in the uptake path, and an oil-fired furnace section sits alongside or below it, sharing the same water and steam space. This saves deck space and one set of mountings compared with two standalone units, at the cost of a more complex internal layout that both duties must be designed around simultaneously.
Main components
Steam drum
Common to both firing modes, it separates steam from water and provides the surface for level control that both sections rely on for safe operation.
Exhaust gas tube bank
Finned or bare tubes arranged in the exhaust uptake, sized against the main engine's exhaust gas flow and temperature at normal sea speed.
Oil-fired furnace
A conventional burner, forced draft fan and refractory-lined furnace, functionally independent of the exhaust section but drawing from and returning to the same drum.
Soot blowers
Fitted to the exhaust gas tube bank specifically, since soot fouling there is continuous during sea passage and left unchecked chokes gas-side flow within weeks.
Selection and sizing
Sizing balances two duty points: exhaust gas heat recovery at the engine's normal continuous rating, and oil-fired steam demand in port with the main engine stopped or idling. Undersizing the oil-fired section to save space leaves the ship short of steam for cargo heating or tank cleaning in port; undersizing the exhaust section wastes recoverable heat at sea. The two sections also need independent safety valve and water level protection, since a fault on one side must not disable steam production from the other.
Regulations and class
Boiler safety valves, water level alarms and low-water fuel cutoffs fall under class boiler rules, and the combined vessel needs class approval covering both firing modes as a single pressure system. SOLAS Ch. II-2 requirements for boiler room fire protection and fuel oil system arrangements apply to the oil-fired section in the same way as for a standalone boiler.
Typical faults
- Exhaust gas side soot fire — cause: soot blower failure or neglected cleaning during long low-load running; consequence: uncontrolled temperature rise, tube damage, potential hull fire
- Uneven water circulation between sections — cause: poor internal baffle design or scaling; consequence: localised overheating and tube failure on one side while the other runs normally
- Burner flame failure — cause: fuel oil viscosity out of range or nozzle fouling; consequence: loss of port steam supply, delayed cargo operations
- Feedwater contamination — cause: shared drum concentrates scale-forming impurities faster than a single-duty boiler; consequence: accelerated tube scaling on both sections
What to look for in a supplier
- Independent safety valve and level protection proven for each firing mode, not a single shared safety train
- Soot blower coverage and access matched to the exhaust gas tube layout, not a generic add-on
- Documented steam output curves for exhaust-only, oil-only and combined firing
- Feedwater treatment guidance specific to the combined drum's higher fouling risk
Log soot blower operation on the exhaust section as strictly as any critical machinery task, because the composite design means a soot fire there threatens the boiler's only oil-fired steam source too, not just the economiser.
2 manufacturers · 3 models
Alfa Laval
2
Mission OS
5-15 t/h steam
· Oil → Steam
· vertical oil‑fired composite boiler
Medium
Oil → Steam
Type
Composite Oil Section
Technical Specifications
- Dampfkapazität OL
- 12.500–55.000 kg/h (mit BOG-Management)
- Dampfkapazität D
- 25–120 t/h (Tanker-Hauptkessel)
- Designdrücke
- 9 oder 18 bar(g)
- Konstruktion
- Zweritrommel (Dampftrommel/Wassertrommel), Membranwände, Generatorröhrenbank
- Rohrsystem
- Gerade Pin-Tubes mit Schwenk-Pins, externe Fallrohre (Aalborg D)
- Brenner-typ
- Oelgefeuert (Standard), Dual-Fuel optional, KBSD/Aalborg-Brenner
- Refraktär
- Minimal im Feuerraum, Isolations- + Formrefraktär an Rohrplatte
Product Lines
- Aalborg OL (12.5-55 t/h, 9/18 bar)
- Aalborg D (25-120 t/h, 18 bar, Tanker-Design)
- Aalborg OM (8-45 t/h, Mittelkapazität)
- Mission OS (bis 6 t/h, Vertical Auxiliary)
Boiler Type
Alfa Laval Aalborg Ölgefeuerte Schiffsdampfkessel (Water Tube / D-Type)
Common Failures & Inspection Points
- Area: Rohrkörper-Leckage durch Korrosion, Pitting, Ablagerungen (Kalkstein/Schlamm) oder VerschleißCheck: Innenseitige Sichtprüfung aller Dampf-/Wasser-Röhren; bei Verdacht Druck-Test durchführen; leckendes Rohr mit konischem Stopfventil nach Stahlbürsten-Reinigung der Rohrenden abdichten. Undichte Rohre müssen erneuert werden.
- Area: Wasserstandsregulation: Ausfalls des Differenzdruck-Transmitters oder Speisewasser-Regelventils führt zu Überflutung/TrockenlegungCheck: DP-Transmitter-Einheit prüfen (externe Referenz/Variable Schenkel, 4–20 mA-Ausgang); Speisewasser-Regelventil Funktionsprüfung; Schauglas auf Risse, Verschmutzung; Alarm-Funktion im Steuergerät testen
- Area: Sicherheitsventil-Versagen oder falsche Öffnungs-/Schließdrücke — Überdruck oder mangelnde Notfall-DampfablastungCheck: Zwei Sicherheitsventile unter Volllast-Dampf prüfen: Druckaufbau 7 Min. max. +6% Arbeitsdruck zulässig (Wasserrohre); Pop-Point jedes Ventils max. ±3% von Einstelldruck; Klassenvermerk: Öffnungs- + Akkumulations-Test unter Klassifizierer-Aufsicht durchführen
- Area: Feuerraum-Refraktärschäden (Risse, Abschilferungen) oder Soot/Korrosion → Wärmelecks, Furnace-Instabilität, Drumm-ÜberheizungCheck: Furnace-Wände und Refraktärbelag visuell inspizieren (mind. 2x/Jahr); auf Risse, Feuchte, Soot-Ablagerungen prüfen. Untere Rohrplatte (Isolations- + Formrefraktär) überprüfen. Nach 3–4 Wochen Betrieb: Blow-Down durchführen, Kessel inspizieren/reinigen, Schlamm entfernen
- Area: Druck-Integritätsverlust durch Korrosion, Risse, Niete oder Schweißnähte → Leckage, Betriebsverlust, SicherheitsrisikoCheck: Hydrostatic Test: Kessel mit Wasser 21–65 °C füllen (Wasserrohre max. 71 °C). Druck: 1,5× MAWP (nicht eintretbar) oder 1,25× MAWP (eintretbar). Sicherheitsventile mit Klammern sichern. Alle Dichtflächen, Niete, Schweißnähte auf Lecks prüfen. Klassenvermerk: alle 2 Jahre (bis 8J), dann jährlich.
- Area: Innen-Korrosion (Wasser-Seite), Kesselstein-Ablagerungen oder Feuer-Seite-Soot/Flockung → Rohrverschleiß, Wärmeverlust, KontaminationCheck: Class Survey: Wasser-Seite (Dampftrommel, Wassertrommel, alle Röhren) auf Korrosion/Risse/Ablagerungen prüfen; Feuer-Seite (Furnace, Fluegas-Bahn) auf Soot/Flockung kontrollieren (mind. 2x/Jahr). Mannlöcher (oben/unten) erlauben Zugang. ggf. Ultraschall/Endoskop für tiefere Defekte einsetzen.
Typ-universelle Inspektionspunkte fuer Alfa Laval Aalborg Ölgefeuerte Schiffsdampfkessel (Water Tube / D-Type) (Aalborg + Class/eCFR, 2026-06). Per-Modell-Specs nicht auto-gefuellt.
Service: Part of Mission composite boiler system. Oil section used in port. Water treatment per Alfa Laval guidelines.
Spare Parts: Aalborg Industries (Alfa Laval): Brennerdüsen-Satz, Photoauge und Dichtungen an Bord vorhalten. Lead time: 3-8 Wochen für Rohre.
Strengths
- Small footprint with vertical orientation fits confined engine‑room spaces.
- Fast start‑up and high part‑load efficiency due to low water content design.
- Optional dual‑fuel capability provides flexibility when oil supply is limited.
- Alfa Laval membrane walls and pin‑tube bank give excellent heat transfer and rapid steam generation.
- Classified by major societies (ABS, DNV GL) and USCG type approved, simplifying regulatory compliance.
Weaknesses
- Maximum output of only 6 t/h limits suitability for vessels with high steam demand.
- Primarily oil‑fired; dual‑fuel option adds cost and complexity.
- Composite construction requires strict water treatment to prevent corrosion and scale.
- Pin‑tube bank inspection and cleaning can be more labor‑intensive than fire‑tube designs.
- Not intended for continuous full‑load operation on large tankers or bulk carriers.
Typical Vessels:
Product tanker (small/medium)Offshore supply vesselPassenger ferryContainer feederNaval auxiliary ship
Certifications:
ABSDNV GLUSCG Type Approval
Decision Guide: Choose the Mission OS when a vessel needs a compact, fast‑responding boiler for low to moderate steam loads and has limited engine‑room space; avoid it on ships that require high continuous steam output or prefer a pure dual‑fuel system without oil‑only baseline.
Use Cases: Typically installed as an auxiliary boiler on vessels that run their main boilers at sea but need reliable steam generation while in port, for hotel services, cargo heating, or BOG handling on product carriers. Its vertical design allows placement alongside other equipment in tight engine rooms of offshore supply ships and small tankers.
Mission OC
5-12 t/h steam
· Oil + Exhaust Gas → Steam
· Composite oil‑exhaust‑gas boiler
Medium
Oil + Exhaust Gas → Steam
Type
Composite Combined
Technical Specifications
- Dampfkapazität OL
- 12.500–55.000 kg/h (mit BOG-Management)
- Dampfkapazität D
- 25–120 t/h (Tanker-Hauptkessel)
- Designdrücke
- 9 oder 18 bar(g)
- Konstruktion
- Zweritrommel (Dampftrommel/Wassertrommel), Membranwände, Generatorröhrenbank
- Rohrsystem
- Gerade Pin-Tubes mit Schwenk-Pins, externe Fallrohre (Aalborg D)
- Brenner-typ
- Oelgefeuert (Standard), Dual-Fuel optional, KBSD/Aalborg-Brenner
- Refraktär
- Minimal im Feuerraum, Isolations- + Formrefraktär an Rohrplatte
Product Lines
- Aalborg OL (12.5-55 t/h, 9/18 bar)
- Aalborg D (25-120 t/h, 18 bar, Tanker-Design)
- Aalborg OM (8-45 t/h, Mittelkapazität)
- Mission OS (bis 6 t/h, Vertical Auxiliary)
Boiler Type
Alfa Laval Aalborg Ölgefeuerte Schiffsdampfkessel (Water Tube / D-Type)
Common Failures & Inspection Points
- Area: Rohrkörper-Leckage durch Korrosion, Pitting, Ablagerungen (Kalkstein/Schlamm) oder VerschleißCheck: Innenseitige Sichtprüfung aller Dampf-/Wasser-Röhren; bei Verdacht Druck-Test durchführen; leckendes Rohr mit konischem Stopfventil nach Stahlbürsten-Reinigung der Rohrenden abdichten. Undichte Rohre müssen erneuert werden.
- Area: Wasserstandsregulation: Ausfalls des Differenzdruck-Transmitters oder Speisewasser-Regelventils führt zu Überflutung/TrockenlegungCheck: DP-Transmitter-Einheit prüfen (externe Referenz/Variable Schenkel, 4–20 mA-Ausgang); Speisewasser-Regelventil Funktionsprüfung; Schauglas auf Risse, Verschmutzung; Alarm-Funktion im Steuergerät testen
- Area: Sicherheitsventil-Versagen oder falsche Öffnungs-/Schließdrücke — Überdruck oder mangelnde Notfall-DampfablastungCheck: Zwei Sicherheitsventile unter Volllast-Dampf prüfen: Druckaufbau 7 Min. max. +6% Arbeitsdruck zulässig (Wasserrohre); Pop-Point jedes Ventils max. ±3% von Einstelldruck; Klassenvermerk: Öffnungs- + Akkumulations-Test unter Klassifizierer-Aufsicht durchführen
- Area: Feuerraum-Refraktärschäden (Risse, Abschilferungen) oder Soot/Korrosion → Wärmelecks, Furnace-Instabilität, Drumm-ÜberheizungCheck: Furnace-Wände und Refraktärbelag visuell inspizieren (mind. 2x/Jahr); auf Risse, Feuchte, Soot-Ablagerungen prüfen. Untere Rohrplatte (Isolations- + Formrefraktär) überprüfen. Nach 3–4 Wochen Betrieb: Blow-Down durchführen, Kessel inspizieren/reinigen, Schlamm entfernen
- Area: Druck-Integritätsverlust durch Korrosion, Risse, Niete oder Schweißnähte → Leckage, Betriebsverlust, SicherheitsrisikoCheck: Hydrostatic Test: Kessel mit Wasser 21–65 °C füllen (Wasserrohre max. 71 °C). Druck: 1,5× MAWP (nicht eintretbar) oder 1,25× MAWP (eintretbar). Sicherheitsventile mit Klammern sichern. Alle Dichtflächen, Niete, Schweißnähte auf Lecks prüfen. Klassenvermerk: alle 2 Jahre (bis 8J), dann jährlich.
- Area: Innen-Korrosion (Wasser-Seite), Kesselstein-Ablagerungen oder Feuer-Seite-Soot/Flockung → Rohrverschleiß, Wärmeverlust, KontaminationCheck: Class Survey: Wasser-Seite (Dampftrommel, Wassertrommel, alle Röhren) auf Korrosion/Risse/Ablagerungen prüfen; Feuer-Seite (Furnace, Fluegas-Bahn) auf Soot/Flockung kontrollieren (mind. 2x/Jahr). Mannlöcher (oben/unten) erlauben Zugang. ggf. Ultraschall/Endoskop für tiefere Defekte einsetzen.
Typ-universelle Inspektionspunkte fuer Alfa Laval Aalborg Ölgefeuerte Schiffsdampfkessel (Water Tube / D-Type) (Aalborg + Class/eCFR, 2026-06). Per-Modell-Specs nicht auto-gefuellt.
Service: Integrated composite design. EG section at sea, oil section in port or supplementary. Soot blow EG section regularly.
Spare Parts: Aalborg Industries (Alfa Laval): Brennerdüsen-Satz, Photoauge und Dichtungen an Bord vorhalten. Lead time: 3-8 Wochen für Rohre.
Strengths
- Integrated dual‑fuel (oil + exhaust gas) capability provides fuel flexibility and BOG utilization.
- High steam output (12.5–120 t/h) suitable for main propulsion boilers on tankers and large bulk carriers.
- Compact D‑type water‑tube construction with membrane walls reduces overall plant footprint.
- Minimal fire‑box refractory lowers weight and simplifies furnace maintenance.
- Design pressure options (9 or 18 bar) match most merchant‑ship steam system requirements.
Weaknesses
- Complex control strategy for simultaneous oil and exhaust‑gas operation increases commissioning effort.
- Higher capital cost compared with single‑fuel water‑tube boilers.
- Regular soot‑blowing of the EG section is required to maintain heat transfer efficiency.
- Limited to 9–18 bar design pressure; not suitable for high‑pressure (≥20 bar) applications.
- Tube bundle maintenance can be intensive due to corrosion or scale if water chemistry is poor.
Typical Vessels:
Crude oil tankerProduct tankerBulk carrierContainer shipRo‑Ro vessel
Certifications:
ABSDNV GLLloyd’s Register
Decision Guide: Choose the Mission OC when you need a versatile steam generator that can exploit exhaust‑gas heat at sea and switch to oil in port, require up to 120 t/h of steam at moderate pressure, and value compact D‑type construction. Avoid it if your vessel operates at pressures above 18 bar, you prefer a single‑fuel system for simplicity, or budget constraints preclude the higher upfront cost.
Use Cases: Typical deployments include crude oil tankers using boil‑off gas (BOG) to generate steam while underway and switching to oil when in port, product tankers that need auxiliary steam for cargo heating, and large bulk carriers that recover exhaust‑gas heat to reduce fuel consumption on long voyages. The boiler’s dual‑fuel capability also suits container ships seeking to lower emissions by maximizing exhaust‑gas utilization.
Kangrim
1
KCB Series
3-10 t/h steam
· Oil + Exhaust Gas → Steam
· Composite oil/exhaust‑gas boiler
Medium
Oil + Exhaust Gas → Steam
Type
Composite
Common Failures & Inspection Points
- EG section soot fire
- Oil burner ignition failure
- Tube corrosion
- Water side scale buildup
Service: Korean composite design. Same soot fire prevention protocols. Annual survey per class rules.
Spare Parts: Kangrim: Brennerdüsen-Satz, Photoauge und Dichtungen an Bord vorhalten. Lead time: 3-8 Wochen für Rohre.
Strengths
- Dual‑fuel capability (oil + exhaust gas) improves fuel flexibility and reduces bunker consumption.
- Higher thermal efficiency by recovering waste heat from engine exhaust gases.
- Compact footprint compared with separate oil‑only and waste‑heat boilers, saving space on board.
- Designed for easy integration with existing marine propulsion systems and steam distribution networks.
Weaknesses
- Complex control system requires skilled operators and more rigorous maintenance routines.
- Potential soot fire risk in the exhaust‑gas section if soot management protocols are not strictly followed.
- Oil burner ignition failures can occur if fuel quality or pre‑heat systems are inadequate.
- Corrosion of water‑side tubes and scale buildup demand regular chemical cleaning and inspection.
Typical Vessels:
Crude oil tankerProduct tankerBulk carrierContainer ship (large, steam‑heated cargo holds)Offshore supply vessel
Certifications:
IMO D-2
Decision Guide: Choose if: you need a single boiler that can simultaneously use oil and recover exhaust heat to lower fuel costs, space is limited, and the vessel operates on routes where dual‑fuel flexibility adds operational resilience. Avoid if: crew lack experience with composite boiler control systems, or the ship’s design cannot accommodate the required soot‑fire prevention equipment and regular water‑side cleaning.
Use Cases: The KCB Series is commonly installed on tankers and bulk carriers that require steam for cargo heating, fuel oil heating, and auxiliary services while also seeking to capture waste heat from main engines. It is favored in fleets aiming to reduce bunker consumption and meet stricter emission regulations by maximizing energy recovery.