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Sulzer

7RTA84T

Name: Sulzer 7RTA84T
Brand: Sulzer
SKU: OSE-38670

The Sulzer 7RTA84T is a low‑speed, two‑stroke marine diesel engine delivering 26 740 kW at 76 rpm, designed for direct‑drive main propulsion on large commercial vessels.

26740.0 kW

Power

Engine Specifications

Cylinders

840 mm

Bore

2400 mm

Stroke

26,740 kW

MCR Power

76.0 rpm

MCR RPM

2-stroke

Stroke Type

Family: Sulzer RTA · Tier: IMO Tier I · Fuel: HFO, MDO

Inspector Detail ✓ verified

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Designation decoded

Sulzer 7RTA84T – 7-Zylinder, Zweitakt-Kreuzkopfmotor, Bohrung 840 mm, Hub 2400 mm, T=Tanker-Ausführung, zahnradgetriebene Nockenwelle

Background

The 7RTA84T is a slow-speed two-stroke marine diesel engine of the Sulzer RTA series with gear-driven camshaft. The T designation indicates tanker optimization, designed for constant load operation at low speeds. Equipped with Variable Injection Timing (VIT), Pulse Lubrication System and Cylinder Liner Undercut (CLU). The 840 mm bore diameter requires dry-dock access for piston and cylinder liner work. As a 7-cylinder configuration, special attention to torsional vibrations is required.

Calculated metrics

Stroke To Bore Ratio

2.857

Inspector checklist

Camshaft and gear drive

Zahnflankenspiel der Antriebszahnräder messen
Inspect camshaft bearings for wear and running traces
Inspect cam profile for pitting and wear
Schmierölversorgung der Zahnräder verifizieren

VIT system and fuel injection

Check VIT actuator stroke and response time
Inspect fuel injection nozzles for dribble and spray pattern
Measure fuel pump plunger for wear
VIT-Referenzwerte mit Sollkurve abgleichen

Pulse lubrication and CLU

Zylinderschmierölmenge pro Hub verifizieren
CLU-Unterschnitt der Laufbuchse auf Zustand prüfen
Schmierölquills auf Verstopfung kontrollieren
Document oil quality and alkalinity number (BN)

Piston and running gear liner

Measure piston rings for wear and tension
Document cylinder liner wear (ovality and conicity)
Inspect piston crown for cracks and erosion
Trockendock-Anforderungen für 840-mm-Komponenten beachten

Torsionsschwingungen (7-Zylinder)

Check torsional vibration damper for silicone oil level and condition
Gesperrte Drehzahlbereiche im Betriebsprotokoll verifizieren
Kurbelwellendurchbiegungen (Deflections) messen
Schwingungsüberwachungssystem auf Funktionsfähigkeit testen

Logbook reference values

Parameter	Expected	Deviation means
Zylinder-Abgastemperatur	320–380 °C at rated load	Deviation > 30 °C between cylinders indicates injection or valve problems
Spülluftdruck	2.5–3.2 bar at rated load	Low pressure indicates turbocharger fouling or charge air cooler leakage
Kühlwasser-Austrittstemperatur Zylinder	78–85 °C	Elevated temperature may indicate cylinder liner cracks or seal failure
Kolbenkühlöl-Austrittstemperatur	50–65 °C	Excessive values signal piston crown overheating or restricted oil flow
Zylinderdruckverlauf (pmax)	130–150 bar (lastabhängig)	Low values indicate VIT misadjustment or compression deficit
Zylinderschmierölverbrauch	0,9–1,3 g/kWh	Excessive consumption indicates ring wear or incorrect dosing
Kurbelwellendurchbiegung	±0,05 mm (herstellerabhängig)	Limit value exceedance indicates bearing wear or foundation deformation

Common Failure Modes

Laufbuchsenriss im CLU-Bereich

Symptoms: ['Kühlwasserverlust', 'Wassernachweis im Spülluftkanal', 'Druckabfall im Kühlsystem']

Causes: Thermische Spannungen im Unterschnitt-Bereich, Material fatigue after extended operating time, Unzureichende Zylinderschmierung

Preventive: Regular cylinder liner inspection by endoscope and ultrasonic, particularly in CLU area; maintain lubricating oil quantity per manufacturer specification

VIT-Aktuator-Versagen

Symptoms: ['Ungleichmäßige Zylinder-Druckverteilung', 'Erhöhter spezifischer Kraftstoffverbrauch', 'Abgastemperatur-Spreizung zwischen Zylindern']

Causes: Hydraulikölverschmutzung, Ventilsitz-Erosion im Aktuator, Steuerungselektronik-Defekt

Preventive: Monitor hydraulic oil filtration, perform VIT calibration at each major inspection

Torsionsschwingungsschaden (7-Zylinder-spezifisch)

Symptoms: ['Ungewöhnliche Vibrationen im gesperrten Drehzahlbereich', 'Rissbildung an Kurbelwangen', 'Dämpfer-Überhitzung']

Causes: Betrieb im gesperrten Drehzahlbereich, Wear of torsional vibration damper, Inadequate damping due to silicone oil aging

Preventive: Gesperrte Drehzahlbereiche strikt einhalten, Dämpfer gemäß Wartungsintervall überholen

Gear-drive wear of camshaft

Symptoms: ['Metallpartikel im Schmieröl', 'Veränderte Steuerzeiten', 'Geräuschentwicklung am Zahnradkasten']

Causes: Lubricating oil deficiency or degradation, Fehlausrichtung der Zahnräder, Material fatigue at high operating hours

Preventive: Lubricating oil analysis at regular intervals, measure gear flank clearance during class survey

Expert tips

💡 Bei 7-Zylinder-RTA-Motoren immer den Torsionsschwingungsdämpfer mit erhöhter Priorität inspizieren – die 7-Zylinder-Konfiguration ist besonders anfällig für Torsionsschwingungsprobleme
💡 840-mm-Bohrung erfordert Trockendock für Kolben-/Laufbuchsenwechsel – Dockplanung rechtzeitig mit Klassegesellschaft abstimmen
💡 Pulse-Lubrication-Quills inspect for free passage at every cylinder inspection – clogged quills lead to accelerated cylinder liner wear

Related components

Turbocharger and charge air cooler Exhaust valve and valve spindle Fuel injection pump and nozzles Torsionsschwingungsdämpfer Nockenwellen-Zahnradantrieb Main bearing and crankshaft Kolbenkühlölsystem Zylinderkühlwassersystem

Classification & regulatory

Dry-dock inspection according to class regulations for 840 mm bore. Torsional vibration analysis according to IACS UR M68 for 7-cylinder configuration to be documented. VIT calibration and emission values according to MARPOL Annex VI / NOx Technical Code verify.

Reference content for inspector orientation. Always verify against manufacturer's manual, latest service letters and class society requirements.

Other Cylinder Configurations 50

Components & Design

Component data being added…

Technical Data

unified from engine model True

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Manuals

operating
Sulzer RTA Operating Manual
Wärtsilä Switzerland (historical Sulzer)
maintenance
Sulzer RTA Maintenance Manual
Wärtsilä Switzerland (historical Sulzer)
spare_parts
Sulzer RTA Spare Parts Catalogue
Wärtsilä Switzerland (historical Sulzer)

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Equipment Model #38670 · ✓ still in production