NR-S NR17/S

Common issues

• Bearing wear (axial and radial play exceeding limits) leading to rotor contact or vibration.
• Compressor fouling due to intake air contamination or oil carry-over, reducing efficiency and causing surging.
• Turbine fouling (carbon deposits) due to exhaust gas quality, especially with HFO, leading to reduced efficiency and high exhaust back pressure.
• Oil leaks from bearing housing seals, oil supply/drain lines, or casing joints.
• Exhaust gas leaks from turbine casing joints, expansion bellows, or gas inlet/outlet flanges.
• Rotor imbalance or damage (e.g., foreign object damage - FOD, erosion, corrosion) causing excessive vibration and potential catastrophic failure.
• Surging, often indicated by a 'whooshing' sound, caused by engine load changes, air filter blockage, or severe fouling.
• Cracks in turbine casing or exhaust gas manifold due to thermal stress or vibration.

Inspection checklist

• Rotor Axial & Radial Play: Check with a dial gauge. Typical new axial play: 0.15-0.30 mm; radial play: 0.30-0.50 mm. Compare against wear limits.
• Rotor Free Rotation: With engine stopped, manually spin the rotor to check for smooth, resistance-free movement and absence of rubbing.
• Compressor Wheel Condition: Inspect blades for dirt, erosion, nicks, bending, or signs of rubbing against the casing. Check air filter cleanliness.
• Turbine Wheel Condition: Inspect blades for carbon deposits, erosion, cracks, bending, or FOD. Check for signs of rubbing against the nozzle ring or casing.
• Bearing Housing & Oil System: Check for oil leaks, verify oil pressure and temperature (if separate system), and inspect oil filter condition.
• Exhaust Gas Casing & Connections: Inspect for cracks, hot spots, gas leaks at flanges, expansion joints, and insulation integrity.
• Mounting & Supports: Verify tightness of all mounting bolts, condition of anti-vibration mounts, and integrity of support structures.
• Drainage Lines: Ensure all drain lines (compressor wash, oil) are clear and free from blockages.
• Nozzle Ring Condition: Inspect for fouling, damage, or deformation (if accessible without major dismantling).

Service intervals

Typical wear limits

Ranges are typical for this design class. Always confirm against the manufacturer documentation for your serial number.

Critical spares

• Complete Bearing Set (Thrust and Journal Bearings)
• Sealing Rings (Labyrinth seals, piston rings for gas/oil separation)
• Gasket and O-ring Kit for bearing housing and casing joints
• Oil Filter Elements (if applicable to TC's dedicated oil system)
• Locking Plates/Washers for critical fasteners
• Compressor Cleaning Nozzles/Equipment (if not permanently installed)
• Emergency Repair Kit (e.g., blind flanges for exhaust gas inlet/outlet in case of TC failure)

Safety

• High Rotational Speed: Rotor speeds can exceed 50,000 RPM; potential for catastrophic uncontained failure (bursting) if bearings fail.
• High Temperatures: Exhaust gas temperatures can reach 500-600°C; severe burn hazard from hot surfaces and exhaust gas.
• Hot Oil: Lubricating oil can be hot (60-80°C); burn hazard during maintenance or if leaks occur.
• Noise Hazard: High noise levels during operation require mandatory hearing protection in the vicinity.
• Pressurized Systems: Compressed air and exhaust gas are under pressure; potential for injury during maintenance or if leaks occur.

Class survey

Class surveyors typically verify operational performance (stable operation, no surging, correct boost pressure for engine load), inspect external condition for leaks (oil/gas), check integrity of lagging/insulation, confirm secure mounting, review logbook entries for maintenance and performance data (boost pressure, exhaust temp before/after TC), and ensure safety devices (e.g., overspeed trip, alarms) are functional and correctly set. They also check for compliance with SOLAS/MARPOL regulations regarding machinery and emissions (indirectly via engine performance).

Estimated lifetime: 16,000 - 24,000 hours before major overhaul (bearings, seals, cleaning, balancing). Total design life of major components can exceed 100,000 hours with proper maintenance and component replacement.