Early Signs & Causes of Cylinder Scoring in Diesel Generators
Early Signs & Causes of Cylinder Scoring in Diesel Generators
Cylinder scoring (piston seizure) is a critical failure mode in diesel generators that can escalate from accelerated wear to catastrophic engine damage. Cummins engineers identify the following diagnostic indicators and root causes:
Early Warning Signs of Cylinder Scoring
1.Temperature Spikes:
2.Abnormal Sounds:
Metallic scraping from piston-ring/liner contact
"Knocking" at TDC (Top Dead Center)
3.Performance Issues:
RPM drop >10% under load
Automatic shutdowns
4.Visual Clues:
Smoke/heat from crankcase or scavenge air box
8 Primary Causes of Cylinder Scoring
1. Lubrication Failures
Low oil delivery: Faulty injectors/clogged ports (flow <80% spec)
Oil degradation:
Mixed lubricant grades (e.g., mixing SAE 40 with synthetic)
Soot contamination (TBN <5)
2. Improper Break-In
<50h violation:
Bearing clearance not stabilized (should be 0.03-0.05mm)
Premature 100% loading causes micro-welding
3. Cooling System Defects
Scale buildup: Hard water deposits reduce heat transfer by 40%
Cummins 6BT5.9 specific:
Only use distilled water + antifreeze mix (50/50)
Tap water causes silicate dropout → coolant passage blockage
4. Piston Ring Issues
Gap errors:
End gap <0.4mm → thermal expansion fracture
Side clearance >0.15mm → blowby carbon accumulation
Material fatigue: Chrome-plated rings last 2x longer than cast iron
5. Mechanical Assembly Errors
Missing piston pin circlips: Allows axial movement → liner scratches
Over-tight pins: Distorts piston ovality by >0.1mm
6. Overloading
>10% continuous overload:
Exhaust temps >600°C (1112°F) glaze cylinder walls
Accelerated carbon buildup
7. Poor Fuel Quality
Cetane <45: Incomplete combustion → acidic deposits
Contaminants:
Water >500ppm → injector corrosion
Particulates >10μm → abrasive wear
8. Operational Mistakes
Cold-start abuse:
0W-40 oil required below -20°C (-4°F)
Minimum 3min idle before loading
IPv6 network supported
English
français
русский
español
português
العربية
Türkçe
ไทย
Tiếng Việt
Indonesia 
Filipino
