9RTA84T-D

Designation decoded

Sulzer 9RTA84T-D – 9-Zylinder, Reihenbauweise, Zweitakt-Kreuzkopfmotor, 840 mm Bohrung, 3150 mm Hub, T=Tankerausführung, D=Entwicklungsversion (Development) mit verlängertem Hub

Background

The 9RTA84T-D represents the development variant of the RTA84T with significantly extended stroke (3150 mm instead of 2400 mm). The stroke-to-bore ratio of 3.75 is extremely high and demonstrates the development towards ultra-long-stroke engines. The extended stroke increases torque and improves thermal efficiency, but places increased demands on piston rod guidance, crosshead and liner alignment. VIT, pulse lubrication and CLU are integrated. The 9-cylinder configuration with this extreme stroke results in an exceptional overall engine height.

Calculated metrics

Inspector checklist

Logbook reference values

Common Failure Modes

Expert tips

• 💡 The extreme stroke of 3150 mm with 840 mm bore gives an S/B ratio of 3.75 – this requires particular attention to piston rod guidance and stuffing box sealing, as the side forces at the crosshead are considerable.
• 💡 With the D development variant, manufacturer modifications and service bulletin updates may be present that differ from standard configuration – always cross-check the current modification status against the shipyard list.
• 💡 Die verlängerte Expansionsphase verbessert den Wirkungsgrad, erhöht aber die thermische Belastung im oberen Linerbereich – endoskopische Inspektionen in kürzeren Intervallen als beim Standardmodell durchführen.

Related components

Classification & regulatory

The D development variant may have different classification requirements. Check whether special class society requirements apply for experimental or first-series variants. Continuous Machinery Survey (CMS) with shortened intervals may be mandatory. Demonstrate emissions compliance according to IMO Tier II/III. Document all inspection results according to ISM Code.