NA70

Measure axial rotor displacement with slide caliper; 'white-line method': paint white line on shaft, attach magnetic base with electrode, run motor ahead/astern, measure line distance with slide caliper. Should be <0.5 mm (new), max 2 mm. Replace bearing if exceeded.

Visual: inspect black/brown deposits on compressor/turbine blades. Elevated oil outlet temperature. Action: perform water/oil washing procedure. Wash compressor side at ~full load, turbine side at 20–40% load with demineralized water (recommended every 200–250 operating hours). Monitor drain water: clear water = light fouling; dark/granular residue = heavy deposits → more frequent washing required.

Acoustic/RPM: high-frequency whistling/vibration from turbocharger compressor side during part load. RPM monitoring (magnetic sensor on rotor shaft, rpm indicator T110 type). Temperature measurement: dual thermocouple (different response times) in compressor inlet for surging detection through rapid temperature spikes. Inspect nozzle ring for blockage/slagging. After surging: stop engine, check compressor wheel for foreign object damage (FOD analysis). Contact: MAN TC-ASB-Feedback@man-es.com for damage images.

Analyse oil samples: viscosity (±1 grade tolerated), water content <0.2% weight (critical >0.5%), contamination ≤2% weight. Check oil colour & consistency (dark/sludgy oils indicate overheating/contamination). Bearing system before servicing: flush oil backwards (reverse-flushing). Check oil inlet/outlet pipes for corrosion/deposits. Inspect bearing bushes for scratches/discolouration. Open oil drain valves before washing procedures to monitor drain water.

Axial clearance measurement: rotate rotor by hand (engine stopped) — should move easily without binding. Caliper: measure bearing bush inner diameter with slide caliper/gauge, compare with shaft outer diameter. Should yield clearance of 0.08–0.18 mm (typically 0.10–0.18 mm for plain bearings). Inspect bearing bushes for scratches/grooves through DLC coating (dark grey/black surface normal). If exceeded: replace bearing bushes/bearing shell.

Measure with thermometer/infrared pyrometer at turbine outlet pipe & bearing housing surface. Normal: ~350–380°C turbine inlet, bearing housing <150°C surface temperature at full load. Elevated values → compressor fouling, nozzle ring blockage or internal leak in rotor housing. Check housing for cracks/leaks (sooty spots indicate leaks). Temperature trend monitoring: sudden spikes = maintenance trigger.