• This can result from overloading the engine, incorrect fuel injection timing (including issues with the Variable Injection Timing – VIT system), or improper fuel injection quantity. The resulting high pressure stresses the cylinder cover material beyond its elastic limit, leading to cracking.
• Scale formation or deposits in the cooling passages can restrict water flow, causing inadequate cooling and leading to overheating and thermal stress on the cylinder cover.
• Incorrect tightening of cylinder head bolts can lead to uneven stress distribution. Excessive tightening may induce mechanical stress, while insufficient tightening can cause leakage and localized overheating.
• High vanadium and sodium content in fuel oil can cause corrosive wear, weakening the cylinder cover material.
• If jacket cooling water temperature is maintained too low, it can result in high thermal stress during combustion cycles due to rapid temperature gradients.

(ii) Actions to Reduce the Possibility of Future Cracking:

• Regularly monitor cylinder peak pressures and adjust fuel timing, VIT, and load distribution to ensure pressures remain within safe limits.
• Maintain the jacket water temperature within the manufacturer's specified range. Regularly inspect the cooling water system for scale buildup and implement appropriate cleaning procedures (e.g., chemical cleaning) as needed to ensure efficient heat transfer.
• Ensure Cylinder head bolts are tightened to the manufacturer's specified hydraulic pressure to avoid uneven stress distribution or loosening.
• Regularly test the cooling water for quality parameters (e.g., hardness, pH, conductivity) and add appropriate chemicals (e.g., corrosion inhibitors, scale inhibitors) as needed to prevent scale formation and corrosion.
• Use fuel oil with low vanadium and sodium content to minimize corrosion.
• Avoid overcooling by maintaining the cooling water temperature within the recommended range, reducing thermal stress during combustion.

Subject: Increased Cylinder Liner Wear Rate during the past six months

Dear Sir,

This is to inform you that the cylinder liner wear rate has increased appreciably over the past six months. Below is the detailed report outlining the potential causes, immediate actions taken, and planned measures to prevent future occurrences.

Causes:

• Recent bunkers contained high levels of ash, catalytic fines, and sulfur, which are abrasive and corrosive to the liner.
• The jacket water temperature was found to be lower than the recommended range, reducing thermal efficiency and increasing liner wear.
• The lube oil being used had a low TBN, which was unsuitable for high-sulfur heavy fuel oil (HFO).
• The cylinder oil feed rate was insufficient, failing to provide adequate lubrication for the liner.

Immediate Actions Taken:

• The feed rate was adjusted to provide better lubrication for the liner surface.
• The jacket water temperature was brought within the correct operating range to enhance thermal efficiency and reduce stress.
• High-TBN cylinder oil is now being used to neutralize the sulfuric acid produced by high-sulfur fuel oil.

Future Actions:

• Implement routine testing of scavenge drains for iron content to monitor liner wear and detect early warning signs.
• Ensure the procurement and bunkering of fuel with low ash and catalytic fines content.
• Establish strict adherence to maintaining cooling water temperatures within the manufacturer's specified range to prevent thermal stress and excessive wear.

Please let me know if further action is required.

Thanking you,

Yours faithfully,

2nd Engineer

MV xxx

ALTERNATE ANSWER:

(i) Possible Reasons for Cracking:

• Cylinder covers are subjected to very high working stresses from both thermal loading and combustion pressures.
• Excessive cylinder combustion pressure may result in abnormally high mechanical stresses on the cover.
• Excessive thermal stress may occur due to high cylinder temperatures, incorrect cooling, or insufficient cooling, producing large temperature differentials across the cover.
• Incorrect tensioning of cylinder head studs/nuts during assembly may cause local stress concentrations.
• Improper initial tensioning can increase localized stresses on the cover, which may result in cracking at highly stressed areas.

(ii) Actions to Reduce the Possibility of Future Cracking:

• Closely monitor maximum cylinder combustion pressures using indicator cards or peak pressure readings. Compare exhaust temperatures and turbocharger revolutions with engine maker’s reference/sea trial data to ensure values are within limits. If found excessive, load must be reduced.
• Maintain cylinder cooling water temperature within the recommended range—neither excessively hot nor cold.
• Ensure correct tensioning of cylinder head nuts strictly as per maker’s recommendations.
• Maintain proper cooling water treatment to minimize scaling or fouling of cylinder head internal heat transfer surfaces.

M.V Ten

Mumbai

Date:

To,

The Engine Superintendent

Alpha pvt ltd, Denmark

Through the Master & Chief Engineer

Subject: Regarding M/E Cylinder Liner Wear

Respected Sir,

During the recent routine inspection of M/E Unit No. 3 at Mumbai Anchorage (with company and port permission), liner, piston, and piston rings were calibrated. It was observed that liner wear-down was higher than the maker’s recommended value. However, since the wear remained within maximum allowable limits, the liner was not renewed. All other parameters, including piston ring wear-down, were within acceptable limits. The unit was therefore reassembled with the same liner and rings, and operating parameters are being controlled.

Possible Causes Identified:

• Although jacket cooling water (JCW) temperature was maintained at 85°C, slight fouling or scaling may have occurred, reducing heat transfer from the liner.
• The engine has been operating on HFO with 3.5% sulphur content. The current cylinder oil TBN is 70, but the feed rate may have been slightly lower than required.

Immediate Actions Taken:

• JCW temperature for all cylinders is now being maintained slightly higher, between 85°C and 87°C, to improve heat transfer conditions.
• Cylinder oil feed rate has been slightly increased.

Future Preventive Measures:

• Enhanced monitoring of cylinder lubrication and feed rate adjustment to suit fuel sulphur content.
• Continued close monitoring of JCW condition, with improved water treatment program initiated to prevent scaling and fouling.

Yours faithfully,

Second Engineer

M.V. Ten