It is a cylinder that is fitted to the engine block to form the cylinder and is one critical function part that forms the engine interior. In Japan, they are usually called Cylinder Liners, but some countries (companies) call them Cylinder Sleeves.
The cylinder liner is a sleeve in which the piston of an engine reciprocates. The life of a cylinder between its re-bores depends on two main factors:
The use of separate barrels or sleeves, which are known as cylinder liners, provides a long life to the cylinder. These cylinder liners are made of superior material and are fitted in the cylinder block. The liners are removable and can be replaced when worn or damaged. The liners should have good wear resistance and the ability to retain oil to lubricate the surface between the walls and the piston rings.
Function 1- Form the sliding surface. Tightly holds when the valve is seated, preventing compressed gas or combustion gas from leaking into the manifold from between the valve and the Valve Seat.
Function 2- Heat conduction. Reduces vale and cylinder head friction at the same time.
Function 3- Keep airtightness. Prevent compressed gas and combustion gas from leaking out. The liner should not be prone to deformation due to the high pressure/high temperature inside the cylinder.
The cylinder liner is made of special alloy cast iron, which has higher abrasion resistance compared to gray cast iron with flake graphite.
For cylinder liners nickel-chromium iron has been popularly used. The nickel-chromium iron used contains carbon 3.5%; manganese 0.6%; phosphorous 1.5%; Sulphur 0.05%; silicon 2%; nickel 2%; and chromium 0.7%.
To increase the wear resistance, the liners are hardened by heating to 855°C–865°C for 30 to 40 minutes and then quenched in oil. By such heat treatment, the life of the liners is increased to three times as compared with grey iron or cast-iron cylinders.
The cylinder liners or sleeves are of two types:
Dry liners are made in the shape of a barrel having a flange at the top. The flange keeps the liner in position in the cylinder blocks. The liner fits accurately in the cylinder. The perfect contact of the liner with the cylinder block is necessary for the effective cooling of the liner.
Also, the gas pressure, piston thrust, and impact loading during combustion are resisted by the combined thickness of the liner and the cylinder. Therefore, dry liners are thinner having wall thickness varying from 1.5 mm to 3 mm, and are used mostly for reconditioning worn liners. The dry liners are not in direct contact with cooling water.
A wet liner is so-called because the cooling water comes in contact with the liner. This liner is provided with a flange at the top, which fits into the groove made in the cylinder block. To stop leakage of cooling water in the crankcase, the lower end of the wet liner is sealed with the help of sealing rings or packing rings.
As the wet liner has to withstand gas pressure, thrust, and impact loading, the wall thickness of the liner is increased and is made more than that of the dry liner. Generally, the wall thickness of the wet liner ranges from 3 mm to 6 mm.
The outside of the liner is coated with aluminum so that it is protected from rust. The wet liner is better cooled than the dry liner. It is easily removable when it is worn out or damaged.
The cylinder liner, acting as the inner wall of cylinders, forms a sliding surface for the pistons rings while retaining the lubricant within. The most important functions of cylinder liners are the excellent characteristic of the sliding surface and these essential points.
Cylinder liners are an integral part of a multi-cylinder block, most often in a diesel engine, where they define and share the working space and the sliding surface of the piston. The cylinder liner is made of special alloy cast iron, which has higher abrasion resistance compared to gray cast iron with flake graphite.
It is a cylinder that is fitted to the engine block to form the cylinder and is one critical function part that forms the engine interior.
The cylinder liner acts as the inner wall of the cylinder and forms a sliding surface for the piston rings while retaining the lubricant within. The most important function of cylinder liners is the excellent characteristics of a sliding surface.
Cylinder liners may crack because of poor cooling, the improper fit of piston or pistons, incorrect installation, foreign bodies in the combustion space, or erosion and corrosion.
Making liners separately from the engine block allows the use of special higher performance materials than those used for the construction of the block itself. Liners are generally made in special cast iron alloys containing elements with natural lubricating properties, like graphite.
Three basic types of liners are used: hot, dry, and finned. The purpose of each type is to protect the piston from heat and impurities using slightly different methods. Cylinder liners are expensive, precisely manufactured products and are primarily purchased from specialty shops.
A wet liner is properly cooled as it comes in direct contact with the cooling water, whereas a dry liner does not come in direct contact with the cooling water. Hence, the working temperature of a dry liner is more than a wet liner.
Check the cylinder liner for cracks, fretting, or scoring. If any crack, fretting or scoring is detected, the cylinder must be replaced with a new one. If this is not the case, continue looking for cavitation erosion on the liner. Erosion results from poor cooling system maintenance.
