1. Excessive bore wear - the liner bore worn beyond the maker's/Class maximum wear limit (e.g. >0.4-0.6% of bore diameter or the specified max), causing loss of compression, high blow-by and oil consumption.
2. Cracking of the liner - cracks in the bore, at the ports, at the top flange or in the water space (thermal/ fatigue cracks), which cannot be safely repaired.
3. Scuffing/ scoring - deep scoring or scuffing of the bore surface that cannot be honed out within limits.
4. Corrosion/ pitting - severe pitting or corrosion of the bore or water side (e.g. from cooling water or combustion products) reducing strength.
5. Distortion/ ovality - the liner out-of-round or tapered beyond limits, affecting ring sealing.
6. Damage to the port area/ lands - broken or cracked scavenge/ exhaust port lands.
7. Repeated ring/ piston failures attributable to the liner condition.
8. Fatigue/ thermal cracking at the top (crown) of the liner or at the flame ring area.

1. Stop the engine, secure turning gear, drain the jacket cooling water and isolate the water/oil connections to the unit.
2. Remove the cylinder cover (head) complete with its valves/injectors, and land it clear.
3. Remove the piston: disconnect the piston rod from the crosshead (remove the clamp), lift the piston (with rod) out of the liner using the piston lifting rig, and land it on blocks.
4. Remove the stuffing box (piston rod gland) and any liner bottom parts.
5. Mark the liner and the jacket for correct orientation/ port alignment.
6. Disconnect the liner cooling water connections and any liner lifting gear.
7. Break the liner from its seating using the lightweight jacking screws/ liner lifting arrangement (or by heating the jacket/ using a liner puller), then lift the liner out of the jacket with a suitable sling, watching the ports and handles.
8. Clean and inspect the jacket bore and the liner seating.

Fitting:

1. Clean the jacket bore and the liner seating thoroughly; inspect for cracks and verify the water spaces are clear.
2. Fit new O-ring/ soft packing seals in the liner grooves, greased.
3. Lower the new liner into the jacket using a sling, aligning the port marks so the scavenge ports line up with the jacket ports.
4. Seat the liner fully on its seating; check it is not rocking and that the lands align.
5. Refit the stuffing box, reconnect the piston rod clamp, refit the piston (with new rings checked) and the cylinder cover, torquing the studs in sequence.
6. Reconnect the water/oil connections.

Important checks before fitting:

• Liner bore size/ identification and surface finish; correct oversize/ standard.
• Ring/groove dimensions and ring gaps; piston/liner clearance.
• Port alignment marks and the condition of the new sealing rings.
• Cleanliness of the jacket and the liner seating; correct fit-up dimensions.

Important checks after fitting:

• Piston/liner clearance and ring end gaps; ring free movement.
• Scavenge port alignment and the liner lands.
• Pressure test the cooling water side (jacket) for leaks.
• Bar the engine over to confirm free rotation and no tight points.
• Run the unit and check compression, exhaust temperature and cooling water temperature.