1. Excessive bore wear - the liner bore worn beyond the maker's/Class maximum wear limit, 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.
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.
5. Distortion/ ovality - the liner out-of-round or tapered beyond limits.
6. Damage to the port area/ lands - broken or cracked port lands.
7. Repeated ring/ piston failures attributable to the liner condition.

1. Stop the engine, secure the 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, and land it on blocks.
4. Remove the stuffing box/ liner bottom parts as required.
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, then lift the liner out of the jacket with a suitable sling.
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 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.
• 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.

• The liner wear rate is calculated by measuring the liner bore diameter at regular intervals (at survey/ overhaul) and comparing the measurements over time. The bore is measured at several positions (top, middle, bottom) and in two directions (fore-aft and port-starboard) using an internal micrometer/ bore gauge.
• The wear rate (mm per 1000 hours, or mm per year) is calculated as: (current bore diameter - previous bore diameter) / (running hours between measurements) x 1000, or the total wear divided by the running hours.
• The wear rate is compared with the maker's/ Class allowable wear rate. A high wear rate indicates a problem (e.g. poor lubrication, abrasive fuel/ air, ring/ liner incompatibility) that must be investigated. The wear rate is used to predict when the liner will reach the maximum wear limit and need renewal.