Main Engine Lubrication Systems

Main Engine Lubrication

• Lubrication is essential for all machinery onboard ships
• Main Engine Lubrication cools and lubricates internal components
• Friction and heat is reduced, preventing parts from overheating
• Lubrication removes debris and impurities
• Engine lubrication systems distribute oil
• Lubrication extends lifespan of vehicle engines
• Lack of lubrication can cause overheating and seizing

Characteristics of Lubricants

• Different types of engines require distinct lubricants

• High-speed trunk piston engines:

  • Use high-speed trunk piston engine oils and distillate fuels
  • Use filler treatment

• Medium-speed trunk piston engines:

  • Use medium-speed trunk piston engine oils and residual fuels
  • Use centrifuge and filter treatment

• Crosshead engines:

  • Use system oils and residual fuels
  • Use centrifuge and filter treatment

• Water separation:

  • High-speed trunk piston engines are poor for water separation
  • Medium Speed and Crosshead engines are excellent for water separation

• Oil change frequency for high speed trunk piston is at regular intervals, however for medium speed trunk piston and crosshead it is basically never

Lubrication Oil Contamination

• Increased fuel injection pressures raise the risk of crankcase oil contamination
• Deposits from fuel contamination critically affect:
  • Fuel pumps, causing plunger sticking or seizure
  • Piston under crowns, reducing lubricant cooling efficiency
  • Increases in piston crown temperatures result in piston seizures or burn-throughs
• "Black Sludge" describes residual fuel deposits in cooler engine parts
• It consists mainly of asphaltenes precipitated from the oil phase
• It is different from the black sludge in automotive gasoline engines caused by nitro-oxidative degradation
• Viscosity and AN of used oil increases after residual fuel contamination
• Contamination by fuels with low flash points can result in reduced flash points, especially with distillate fuels.

Sludge Formation and Liner Lacquering

• In medium-speed engines, lube oil can be contaminated by combustion blow-by gases or raw fuel dilution
• Modern engines with higher fuel pump pressures may experience increased fuel leakage
• Heavy fuel oil can contaminate lube oil by 2-15%
• Heavy fuel oils contain cracked asphaltenes which do not dissolve but coagulate into sticky asphalt particles of 2-5 microns
• These particles form black deposits on metal surfaces like the cambox and crankcase
• Mixing residual fuels and lubricants can cause asphaltenic particles to coagulate
• This results in sludge formation, clogged oil scraper rings, and increased piston ring groove deposits.
• Sludge can overload lube oil separators and clog filters

Lubricating Oil Contamination

• Lubricant Degradation
• Gaseous contamination:
  • Air:
    • Causes air entrainment (foam)
    • Detected using air release & foam test
    • Leads to cavitation failure in bearing
  • Combustion gases:
    • Causes oil degradation
    • Detected using FTIR
    • Reduces oil life
  • Reaction products:
    • Causes oil degradation
    • Detected using FTIR
    • Reduces oil life
• Liquid contamination:
  • Water:
    • Causes emulsion, leading to additive loss
    • Detected using ICP
    • Leads to reduced corrosion protection
  • Fuel:
    • Causes viscosity and volatility
    • Detected using viscosity of the oil
    • Lead to breathing wear and damage as well as deposits
  • Cylinder oil drain:
    • Leads to increased viscosity and BN
    • Detected using Viscosity and BN tests
    • Can cause potential bearing problems
• Particulate contamination:
  • Dust:
    • Increase in insolubles
    • Detected using ICP, insolubles
    • Risk of abrasive wear
  • Wear debris:
    • Induces catalycity
    • Detected using ICP elements, ferrography
    • Reduces oil life and causes wear
  • Soot:
    • Causes oil thickening
    • Detected using viscosity and insolubles tests
    • Raises centrifuge discharge rate

Lubricating Oil Microbial Contaminations

• Visual symptoms of microbial contamination are:
• Slimy looking crankcase doors
• Rust films
• Honey-coloured films on the journals
• Black stains on whitemetal bearings, pins and journals
• Grey/black deposits on metallic parts
• Corrosion of the purifier bowl
• Sludge accumulation in the crankcase
• Paint stripping in the crankcase