What Is a Cylinder Liner?

What Is a Cylinder Liner?

A cylinder liner is the inner sleeve of the cylinder. It is usually made of a metal alloyed with other elements to increase its strength, hardness, resistance to corrosion and abrasion. Its main function is to prevent the compressed and combustion gas from leaking out through the valve or piston rings as the engine runs. In addition, it helps in providing a smooth and consistent surface for the compression and combustion of air and gas within the cylinder.

The sleeve is generally cast from a grey iron or cast iron alloy that is further strengthened by using other elements to enhance its properties like hardness, toughness and resistance against corrosion and abrasion. It is important for the sleeve to be accurate in terms of its dimensions and specifications when it is fitted inside the cylinder block. If there are any mismatches, there will be excessive thermal stresses and it can cause the sleeve to fracture.

Cylinder liners are generally cooled by the cooling water in the crankcase, and this is why they are called wet liners. They come into direct contact with the coolant, and hence, they are tightly fitted and securely locked at both ends to avoid any leakage of cooling water or coolant. Since wet liners are not supported by the engine block, they have thicker walls compared to dry liners, with their wall thickness ranging from 3 mm to 6 mm.

Both the wet and dry liners are made from materials which are hard and tough to resist against high thermal stressing and abrasion caused by rapid changes in temperature, and they must also have excellent wear resistance. Cylinder liners are also designed to be able to withstand the forces generated by the combustion process. They are also made to be abrasion resistant, and their smooth surface ensures a consistent piston clearance and ring seal.

Wet liners are easier to replace compared to dry ones. However, the liners must be carefully lubricated and kept straight while they are removed. If they are kept on their side for too long, they will be twisted and will not fit properly when installed again. Cylinder liners should be gently lubricated with precise machine lubricant and stored in a clean, dry spot where they can be safely handled.

Cylinder liners can be inspected for signs of scoring, which is a condition where the sleeve is scored by friction between it and the piston rings or with the valve seats. A visual check is a good way to detect such conditions, and they should be inspected at regular intervals. If the sleeve is damaged or shows signs of wear, it must be replaced immediately. If you are preparing for the SSC JE Mechanical or SSC AE Mechanical exam, Testbook has an extensive a library of test series and practice questions that will help you get a clear idea about the subject. Download the app and enroll for a course now to prepare well!

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