.clover leafing

Clover leafing is a form of wear on cylinder liners due to high sulphur content in the fuel oil and when the supply of lube oil is not uniform around the radial bore of the liner.. Clover leafing takes place between each pair of lubricating quills

• Alkaline cylinder oil is used to neutralize acid. 
•  Perfect distribution of cylinder oil is difficult.
• Surfaces get either more alkalinity or less depending on the position of cylinder lubricator quill & TBN used.

If TBN use is more:

• Surfaces near quills will get excessive alkalinity leading to hard calcium compounds formed.
• Alkaline compounds are burnt and formed hard deposits which caused abrasive wear.
• Surfaces far from quills will have alkali neutralized and thus minimum wear is experienced.

If TBN use is less:

• Surfaces near quills will have minimum wear but surfaces far from quills will be starved of alkaline compounds 
• This will lead to acidic corrosion and thus experienced maximum wear ,

This above phenomenon known as clover leafing which can result in blow past and ultimate failure of liner in severe case

Causes of excessive wear:

• Improper running in
• Overloading of engine – overheated and lube oil film breakdown
• Use of low Sulphur fuel (less than 1% Sulphur) in conjunction with high alkaline cylinder oil and vice- versa
• Inefficient combustion -carbon deposits
• Increased piston ring clearance and bad ring profile
• Inadequate lube oil supply
• Lube oil too low in viscosity/ TBN
• Contamination of lube oil by abrasive material (In 4 stroke engines)
• Cylinder liner material unstable –phosphorous/silicon
• Cylinder wall temperature too high or too low – oil film breakdown or corrosive wear.
• Scavenge air temperature too low –corrosive wear
• irregular draining of charge air cooler/ water in the scavenge air