Microbial attacks on crankcase lube oil are due to contamination of oil by water from leaks and condensation, the fuel, atmospheric air, cooling water, and even seawater. Cooling water, in particular, is a biological source of contaminant of crankcase oil. Bacteria are of two types: one grows in the presence of oxygen, and the other does not require oxygen. These microbes thrive in small amounts of water at the oily water interface, and they dislike movement of oil (favourable to grow when lube oil is not circulating, i.e. engine in stopped condition). The ideal temperature condition to grow is 25 - 40C. The additives in lube oil are consumed as nutrients by the bacteria. Under ideal conditions, bacteria grow very quickly.

The microbial attack causes lubricating oil to become slimy and will increase the viscosity, which results in frequent choking of filters, there will be a rotten egg smell and severe pitting corrosion of white metal in the crankcase. Fuel injection will be affected (Electronic engines), leading to misfiring and lack of power. The increased viscosity and an increase in the acidity of lubricating oils will cause overheating and corrosion within the bearings.

To:

The Owner/Operator

M/V Alpha

August PVT LTD.

Singapore

Subject: Microbial Contamination of Main Engine Lubricating Oil

Good Day Sir,

This is to bring to your attention that the lubricating oil of the main engine onboard has been contaminated with microbial growth. Below is a summary of the issue, immediate corrective actions taken, and recommendations to prevent similar occurrences in the future.

The contamination was confirmed based on the following observations:

• A distinct rotten egg smell from the main engine lubricating oil sump and crankcase.
• Milky appearance of oil in the sump and crankcase, along with paint flaking in these areas.
• Black stains observed on white metal bearings, pins, and journals.
• Corrosion of unprotected metal surfaces.
• Frequent clogging of filters due to excessive sludge formation.
• Persistent high water content in the oil even after purification.
• Excessive sludge discharge from the purifier.

Immediate actions have been taken to mitigate the situation:

• LO samples were tested, confirming high water content.
• The complete sump oil was transferred to an empty LO settling tank.
• Batch purification was carried out.
• The LO sump and crankcase were thoroughly cleaned.
• Due to the significant deterioration of the oil, the entire quantity of oil was replaced, in consultation with the Chief Engineer.

To prevent recurrence, the following measures are strongly recommended:

• Regularly drain tanks to remove water.
• Consistently purify oil to maintain quality.
• Ensure regular movement of oil to avoid stagnation.
• Promptly address any water ingress by identifying and rectifying leaks.
• Maintain a higher lubricating oil temperature to inhibit microbial growth.
• Send oil samples for shore analysis at regular intervals to monitor its condition.
• If recommended by the oil manufacturer, introduce biocides and fungicides to inhibit microbial activity.

Please feel free to reach out if further clarifications or updates are required.

Yours Faithfully,

[Your Name]

Second Engineer

M/V Alpha