Gas oil seperator

I have great doubts about functionality of our gas oil separator.

• We are working with a ALFA LAVAL MIB303S-13 PUR (Gas oil only)
• Our trade is Baltic Sea and North Sea areas where water temps are 0-16 degrees Celsius.
• Our fuel tanks are all 35-40% in direct contact with outboard water and the gas oil is almost the same temperature as the outboard water.
• There is no preheating system for the fuel (gas oil) installed.

When I first came on board 2 weeks ago I found that the fuel separator was cleaned once a week. (Approx 130 working hours)

Also I found that the separator was actually not at all dirty inside. I was told that this was a normal situation but I have my doubts.

We had to replace our filters on the main engine within 750 hours which in my opinion shows that the separator does not do a proper job.

Moreover I found that the black ring (for: MDO and Lub oil) was installed instead of the white ring which is specially for gas oil. When I installed the white ring the system did not work. It was leaking fuel, no matter which back pressure I tried.

The system only runs with the black ring and at least 0.8 bar back pressure.

From the past experiences with other separators I know that we had to clean the separator at every two days and I really cannot remember that we had to replace the main engine fuel filters within 750 hours.

Could you please advise with regard to the described situation.