(a) Reason for piston ring breakage:

• Excessive wear in the cylinder liner leads to increased piston ring movement, both radially and axially. This fluctuating motion can cause tilting and eventual breakage of the rings.
• If the piston ring does not exert sufficient pressure on the liner, gas pressure can penetrate between the ring and liner, collapsing the ring into the groove and causing breakage.
• Ridge formation near scavenge pockets can create stress concentrations at the piston ring's radial edge, promoting fracture.
• Jamming or sticking of rings caused by excessive carbon deposits, often due to improper combustion or inadequate cleaning during maintenance.
• Excessive wear in the piston ring grooves causes the rings to impact the groove walls during operation, leading to hammering and eventual breakage.
• Inadequate cylinder lubrication results in overheating and increased friction, weakening the rings and causing breakage.
• Acidic corrosion and high-temperature corrosion weaken the ring material, predisposing them to fracture.
• Excessive engine loading can cause the rings to deform beyond their elastic limit, leading to collapse and breakage.
• Using low-quality or non-manufacturer-specified rings compromises material strength and durability, increasing the risk of breakage.
• Improper installation during ring renewal can lead to misalignment, increased stress, and premature failure.

Minimizing Breakage through Maintenance and Engine Operation:

Maintenance practice:

• Perform routine inspections and overhauls of pistons, piston rings, and cylinder liners as per the PMS schedule.
• During overhauls, ensure piston rings and grooves are thoroughly cleaned, and all necessary clearances are measured to verify proper fit.
• Reuse piston rings only if measurements indicate they are within the safe operational limits until the next overhaul.
• Regularly maintain the fuel injection systems to prevent improper combustion and minimise stress on piston rings.
• Ensure that piston rings and liners are free of marks, scratches, or other signs of wear during scavenge inspections.
• During overhaul, install piston rings with proper tools and techniques, ensuring free movement of rings in their grooves.
• A proper running-in procedure after installing new pistons and rings helps to ensure correct seating and minimises initial wear.

Engine Operation:

• Maintaining adequate cylinder oil lubrication minimises friction and heat generation.
• Maintain appropriate cooling of the cylinder liner and piston to avoid thermal stresses.
• Use properly treated fuel oil and ensure correct operation of fuel pumps, injectors, and Variable Injection Timing (VIT) systems.
• Maintaining correct combustion parameters minimises improper combustion and reduces carbon deposits.
• Keep air filters clean to avoid the ingress of dust and abrasive particles into the engine.
• Avoid overloading the engine, which can stress the piston rings and cause failure.

(b) Consequences of Broken or worn-out piston rings.

• Low compression pressure, Pmax & power developed.
• Blowpast, increase in scavenge temperature and cause scavenge fire.
• Rise in exhaust temperature.
• Scuffing of liner and increase in wear rate.
• Increased SFOC.
• Fouling of turbocharger due to improper combustion.
• Fouling of EGE and can cause EGE fire.
• Damage to cylinder liner due to blowpast.
• Loss of cylinder lubrication.

The following precautions must be taken while operating an engine with broken or severely worn piston rings:

• Isolate the affected unit as excessive blowpast may cause scavenge fire.
• Monitor the scavenge temperature.
• Run the engine at low load till necessary replacement is carried out.