The Best Tutorial On Cylinder Liners Of Marine Diesel Engines

Cylinder Liners of Diesel Engines

In this Post on Cylinder Liners of Diesel Engines, we shall discuss the Cylinder liner function, properties of Cylinder liner material, Types of cylinder liners, Cylinder liner manufacturing process, Difference between cylinder liner and sleeve. The post will be useful for young marine Engineering students and engineers working in industries.

Cylinder Liner function (Cylinder Liners of Diesel Engines)

A cylinder liner is a barrel-shaped part fitted into the cylinder block of an engine to form the part of the combustion chamber where the combustion of fuel occurs. The cylindrical piston reciprocates in the cylindrical space created by the Cylinder liner.

The flame ring is mounted on the upper part of the cylinder liner and scrapes carbon deposits as well as excessive lubricating oil on the piston crown, which contributes to reducing the lubricating oil consumption.

For the following listed reasons, cylinder liners are manufactured separately.

• Due to the reciprocating movement of the piston, the cylinder liner will wear and will need replacement.
• At the operating temperature, the cylinder liner is hotter than the jacket/cylinder blocks. Hence the expansion of the liner will be more than the expansion of the jacket. If the cylinder liner were not made separately, then undesirable thermal stresses would occur, causing fracture of the material?

Difference between Cylinder Liner and Sleeve (Cylinder Liners of Diesel Engines)

Sleeves are mainly used for the repairs of the damaged block. Cylinder Liners are used in an engine that is fitted in the cylinder block.

Types of Cylinder Liners

• Dry Type Cylinder liner
• Wet Type of Cylinder Liner

Dry Type Cylinder liner

In a Dry-type liner, Water doesn’t circulate around the liner

for cooling. Instead, the liner is tightly fitted in the cylinder block. The walls of the dry type liner are thin. As a result, the liner is shrunk in the cylinder block.

Wet Type cylinder line

A wet-type cylinder liner directly contacts the cooling Water, which circulates around the liner for cooling purposes. The circulating Water controls the piston rings and liner temperature. Wet liners will have the cooling surface between the engine cylinder block and the liner. In some cases, there are integral cooling spaces. In wet-type cylinder liners not provided with the integral cooling passages, the water jacket is built by the liner and separate jacket. A stationary seal is provided at both the combustion and crankshaft end of cylinders to arrest the coolant leakage into the oil sump or combustion chamber. Typically the seal towards the combustion chamber end is either a metallic tom back gasket or finely machined surface. On the sump side, neoprene rubber rings are provided for sealing purposes. This will also allow the linear expansion of the cylinder liner. The walls of the cylinder liners of the wet type are strongly built to withstand the working pressure of the combustion process.

Material of Construction

Cylinder liner is manufactured with better material than that of the cylinder block. The cylinder block is manufactured with grey cast iron, and the Cylinder liner is made of centrifugally cast iron copper vanadium alloyed for better lubrication properties due to graphite, corrosion resistance, and wears resistance at high temperatures.

Material Composition for large bore Cylinder liners

Cast iron with , Carbon-3.00%, Magnese-1.00%, Silcon-0.70%, Sulphur-0.10%, Phosphorus- 0.25%, Vanadium- 0.15%,

Manufacturing Methods

1. Sand Casting
2. Centrifugal Casting.

Sand Casting; — This process is adopted for the manufacture of large slow-speed Engines. This process enhanced wearing properties due to the best grain flow formed in casted material — better graphitization enhancing lubricating properties due to steady cooling rate.

Centrifugal Casting- This process is adopted for Medium and high-speed engines. With this process, we achieve robust liner, consistent structure, low wearing quality (due to fast cooling rate).

Manufacturing process

Following activities are undertaken during the liner manufacturing process.

1. Rough Machining
2. Hydro Test ( 7 bars)
3. Ports forming
4. Final machining of the internal and external surface
5. Honing the internal surface- (surface finish approximately to 3.5lm)
6. Surface treatment

Surface Finish Treatment

Surface finish treatment is given to the inner surface of the liner for the piston rings to seat wholly and quickly so that the engine doesn’t use oil. The surface finish should fulfill the Piston ring manufacturer’s standards and maintain the excellent cross-hatch marks on the working surface to retain the lubricating oil and make the lubricating oil available to piston rings.

Cylinder Liner Failures (Cylinder Liners of Diesel Engines)

1. Crack through the Liner flange due to unequal or extra tightening of cylinder heads

2. Inadequate support causing hoop stress crack

3. New piston ring hitting the wear ridge causing circumferential Crack.

4. Flame intrusion causing a crazy crack

5. Cracks across the port bar due to overloading, unsatisfactory cooling, scavenge fire, poor installation of rubbing sealing ring.

Cylinder Liner Repair Chart

Cylinder Liner Wear (Cylinder Liners of Diesel Engines)

1. Abrasion is caused by hard particles produced due to lubricating oil film breakage.
2. Acidic combustion products causing corrosion
3. Metal to metal contact due to boundary lubrication causing scuffing break down.
4. Hard particles derived from airborne dirt, ash contents carbon from combustion due to worn piston rings.
5. Cold corrosion due to the sulfur turning into Acid at dew point.

The procedure of Cylinder Liner Removal

Always adopt the proper method for the removal of the liner. If the right tools and procedures are not used, there are chances of damage to the cylinder liner and cylinder block.

1. Remove the piston and connecting rod
2. Mark identification mark concerning cylinder block.
3. Loosen the cylinder shoes of the cylinder liner lifting tool
4. Put the shoes of the device at the bottom edge of liner
5. Jack up the cylinder liner by turning the nut clockwise.
6. Remove and discard the sealing ring (Tom’s back ring).
7. Remove the cylinder liner lifting tool
8. Remove and dump the cylinder sealing rings.

Important Note;- Always store or place the cylinder in a vertical direction. Else there may be a distortion of the liner. Also, note that the liner marking for the refitting in the unit’s exact location has been removed.

Cylinder liner cleaning procedure (Cylinder Liners of Diesel Engines)

Clean the liner with the following procedure.

1. Wash the liner using the detergent and warm water solution, scrubbing it with a non-metallic brush.
2. Rinse the cleaned liner with steam or hot water
3. Dry the liner with dry compressed air.
4. Smear the bore of the liner with fresh engine oil.
5. Wait for 10 minutes for oil work into the working surface.
6. Wipe the cylinder bore with the clean paper towel
7. Repeat the step 4 through 6 in case the black residue is observed on the towel

Inspection of Liner

Points to be observed while inspecting the cylinder liner

• Check the cylinder liner for cracks, fretting, and scoring.
• Scavenge ports opening with sharp edges,
• Formation of the edge at the top dead center position
• Liner surface with mechanical friction wear impressions and abrasive wear.
• Blow-by dark areas.
• Acidic and cold corrosion marks on the surface
• Lubrication opening with cracks and damages.
• Glazing of liner surface with a diminished indication of honing marks.
• Lube oil flow from lubrication ports
• Gauging of Liner bore for ovality and wear.
• Replace the Liner in case of any cracks, fretting, and scoring is detected.
• Inspect the cylinder liner for any cavitations erosion as per the below figure.

Gauging of the Cylinder liner

Gauging of the cylinder liner is to be carried out at regular intervals mentioned in the OEM manual. The Record of gauging is to be maintained in the form shown below for future reference and wear rate calculation.

The Liner will have to be cleaned inspected thoroughly. The temperature of the Liner bore measuring gauge and Liner should be identical.

In case of temperature difference exceeds or vice versa, then the following multiplying factor will be used.

Liner gauging report format