cylinder liners & covers

Cylinder Liners & Covers

Centrifugal Casting• In centrifugal casting, a

permanent mould is rotated about its axis at high speeds (300 to 3000 rpm) as the molten metal is poured. The molten metal is centrifugally thrown towards the inside mould wall, where it solidifies after cooling. The casting is usually a fine grain casting with a very fine-grained outer diameter.

• Size limits are up to 3m diameter and 15m length.

• Typical parts made by this process are pipes, boilers, pressure vessels, flywheels, cylinder liners and other parts that are axi-symmetric.

Large Slow Speed 2-Stroke Medium Speed 4-Stroke

Liner Condition

Carbon on piston crown

Little on first landNone on 2nd & 3rd

Inspection of Liner

Talcum Powder

Turn engine after covering liner walls with talcum, where there is lack of contact between rings and liner the talcum remains

• Black areas such as this may also be seen

• Could be local blow by, or, as in this case, the result of degraded cylinder oil and possibly partially burnt fuel droplets; known as ‘lacquer marks’

Effect of Wear Edge

Chamfer on top ring from striking wear edge

Removal of Wear Edge

Do NOT use angle grinder!

Damages running surface below wear edge

Removal of Wear Edge• Wear edge should be

removed by a milling tool as shown

Evaluating Wear of Liner(and rings)

Three categories:

• Abrasive

• Adhesive (scuffing)

• Corrosive

Abrasive Wear

• Indicated by scratching of the surface of the liner and rings.

• Caused by abrasive particles brought into the engine – possibly in the fuel: ‘catalytic fines’, or through the air: sand or grit

• Could be a consequence of corrosive or adhesive wear produced particles.

Adhesive Wear/Scuffing

• Adhesive wear occurs when, for some reason, the lubrication film is lost and there is metallic contact between ring and liner. In severe cases this is called scuffing.

In this case caused by blocked drain on air cooler

Corrosive Wear• Corrosive wear is caused

by the formation of sulphuric acid on the liner surface when liner temperature is below dew point and the oil film is broken down

The surface of the liner typically appears spotted

Clover Leafing• Phenomenon where liner wear

varies relative to position of luboil quills

• If allowed to continue will lead to ring collapse

• Liners should be honed as soon as it is noticeable

Hammer marks due to collapsed rings

Hammer marks from broken exhaust valve spindles or piston rings

• Thermal cracks because of bad ring condition

• If atomizers are faulty or wrongly positioned thermal cracking in top of liner can occur

Liner Before Honing

• Thermal cracks because of too great a distance from the running surface to cooling bores!

Honing of Cylinder Liner

Air Motor

Liner After Honing