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 Shatter Cooling Effect (less at slow speed) - piston go up, more pipe length, less pressure
Piston come down, more pressure Crown damage - Thermal stress, mechanical loading
- Direct oxidation
- Catalytic oxidation
- Wet corrosion, water in fuel
| Piston Overheat due to:
- Overloading - excessive fuel
- Poor lubrication - friction more, heat up, water in fuel
- Poor coolant and faulty circulation - pressure and volume, deposits, scale and carbon for oil cooled, engine running slow, no full flow of coolant.
- Faulty injector - impingement - localized burning, star crack. Peel off layer, crazy crack
- Leaky after burning - loop scavenging hot gas return to crown
- Distorted liner or oversized piston - touch and friction, misaligned piston
- Faulty piston ring - blow by of gas
- Insufficient air from turbocharger for cooling
|  | Detection of Piston Overheating
- Occur at slow speed due to coolant not agitated and effectiveness reduced.
- Rise in cooling water return temperature
- Noise in cooling system due to vapor lock
- Crank mist for trunk piston using splash lubrication
- Dry patches and discolorization
- Smoke and smell
| 
| Aluminum piston
- Lose shine if overheated
- White powder oxidized or ash from fuel
Worn groove can be deposited by argon arc method, but cannot do too many times due to weakening of material |  | Piston Ring Material - Made slightly harder than piston
- Ring speed faster, area of contact less
Copper ring
- Loop scavenging for long piston skirt to avoid micro seizure due to piston touching liner
| Ring breakage
- Worn piston ring grooves, not straight, blow past
- Worn cylinder liners blow past
- Deposits in ring grooves, blow past
- Sticking rings blow past
- Combustion knock. Improper timing. Inadequate cetane no. Of fuel
- Local blow by of ring - blocked ring groove, chamfered too much, ring twisted
- Excessive piston clearance - piston slap (move sideways)
- Ring flutter
- Oil of inadequate quality
- Incorrect design of scavenging and exhaust ports, chamfer not proper. (Make narrow so that less length of ring unsupported)
- Incorrect shape of rings - chamfer, no allowance for expansion outwards
|  | Deposits on Piston Rings and Piston due to:
- Improper air filtration
- Improper fuel filtration (gas engine)
- Wet or corrosive gas
- Improper combustion
- High cylinder oil feed rate
- Worn or weak rings
- Incorrect jacket water temperature
- Continuous overload operation
- Blow by of piston ring
- High crankcase vacuum (trunk piston engine)
- High crankcase oil level (trunk piston engine)
| |
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