NR-S NR24/S

Common issues

• Bearing wear and failure (thrust and journal bearings) due to contaminated lube oil, insufficient oil supply, or excessive vibration.
• Fouling of compressor impeller and diffuser, leading to reduced efficiency, surging, and increased exhaust temperatures.
• Fouling of turbine nozzle ring and blades, causing reduced efficiency, higher exhaust back pressure, and potential thermal stress.
• Oil leakage from the bearing casing, often due to worn labyrinth seals, clogged oil drain lines, or excessive crankcase pressure.
• Cracks or erosion in the turbine casing, nozzle ring, or turbine blades, particularly when operating on heavy fuel oil with high vanadium/sulfur content.
• Rotor imbalance caused by uneven fouling, blade damage, or bearing wear, leading to excessive vibration and potential catastrophic failure.
• Surging of the turbocharger, indicating an imbalance between engine load and turbocharger performance, often due to fouling or engine issues.
• Air filter clogging or damage, restricting air intake and leading to compressor fouling and reduced engine performance.

Inspection checklist

• Check for abnormal noise or vibration during operation (e.g., whistling, grinding, rumbling).
• Monitor bearing temperatures (if sensors fitted) and lube oil pressure/flow to the turbocharger.
• Visually inspect compressor and turbine blades for fouling, erosion, or damage through inspection ports (when safe and cooled).
• Check the condition of the air filter element and ensure the intake ducting is clear.
• Inspect all casing joints and connections for exhaust gas or oil leakage.
• Verify the integrity of the insulation blanket on the turbine casing for hot surface protection.
• Check the condition and free flow of the oil drain line from the bearing casing.
• During scheduled maintenance, check axial and radial play of the rotor shaft using a dial gauge against manufacturer's limits.
• Inspect the nozzle ring and diffuser for carbon build-up, erosion, or deformation.

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 set of bearings (thrust and journal bearings)
• Oil seal rings (labyrinth seals) and O-rings
• Gasket set for overhaul (especially for gas-tight joints)
• Air filter elements
• Impeller nut (left-hand thread)
• Nozzle ring (especially for HFO operation, prone to wear/fouling)
• Set of locking plates and washers

Safety

• High surface temperatures (up to 400-600°C) on the turbine casing and exhaust piping – severe burn hazard. Ensure insulation is intact and use appropriate PPE.
• High rotational speeds (up to 60,000-80,000 RPM for NR24/S) – risk of rotor disintegration if severely unbalanced or damaged, leading to shrapnel hazard.
• Pressurized exhaust gas and charge air – leakage can cause injury, fire, or interfere with engine room ventilation.
• Hot exhaust gases during inspection or maintenance – ensure adequate cool-down period and proper ventilation before opening.
• Heavy components during maintenance (casings, rotor assembly) – risk of crushing injuries if not handled with proper lifting gear and procedures.

Class survey

Class surveyors typically verify the last overhaul date and scope from logbook entries and maintenance records. They will inspect the external condition for oil/exhaust gas leaks, insulation integrity, and general cleanliness. Operational checks for abnormal noise/vibration and bearing temperatures may be performed. During special surveys, an opening inspection of the compressor and turbine sides (for fouling, erosion, damage) may be required, along with verification of rotor axial and radial play against manufacturer's limits. Confirmation of critical spare parts availability (especially bearings and gaskets) is also a common check.

Estimated lifetime: 48,000 - 72,000 hours (for the rotor assembly before major replacement consideration, assuming regular maintenance)