ODME – What is ODME? (Part 2)

How does ship crew operate ODME???

ODME is required under Marpol Annex I, which deals with pollution aspects related to oil cargoes.

odme 6.PNG

For easy understand how does it work? We will take an example: a product tanker of 21.8000 DWT which has just discharged an oil cargo of 15000 MT (16000 m3 @ 15 C). This tanker need to clean these tanks which were carrying total oil cargo of 15000 MT. How to proceed with cleaning and decanting the slops with ODME ? It has some below steps:

1 – Set the total oil quantity in ODME:

Marpol has put a limit on how much total oil we can discharge in the wash water. This limit is 1/30000 of the total cargo carried. So:

Total Cargo carried in the tanks to be cleaned : 15000 m3 @ 15 C

Total oil from the washing that can be discharged = 0.5 m3 (500 litres)

Set the total oil limit as 500 litres in ODME

2 – Settling time ( min 36h ) ensures that the oil has separated completely from the water.

We will wash the tanks and collect in slop tank.  Discharge rate is limited to 30L/NM as above mention.

3 – Check discharge condition from Rule:


4 – Preparation condition before start ODME:

  • Check the inlet and outlet valves for flow meter are open
  • Check Fresh water supply is available and all valves are open
  • Check sample line inlet and outlet valves are open
  • Check air supply for pneumatic valves is on.
  • Check cleaning solution is present in the container
  • Check power supply
  • Check sample pump shaft

These values to check are for flow rate, speed and PPM.

5 – Start the cargo pump in cycle mode

6 – Start overboard discharge

After all the above steps are completed and verified, cargo oil can be commence for overboard discharge.

7 – Monitor during oil overboard discharge operation

Pls take note that when you reduce the pump speed to reduce the flow –> with flow rate reduced, the IRD will reduce too.

8 – Stop the overboard discharge:

The ODME will stop automatically when:

  • IRD exceeds 30L/NM or
  • The total oil dischrage exceeds limit

We can stop ODME by manual when either of the following happens

  • Reached the interface level
  • Rapid increase in PPM. Pls check to make sure that oil water interface is still very far.
  • See some oil sheen on the sea surface

When ODME stops automatically:

  • The operator need to wait more 24 hours of settling time to start the ODME again. Now to have the water separate out from oil, we need to allow it 24 hours. A recirculation this would have churned.
  • But if the ODME had stopped because of some error, if the water level was still high, there is no need to wait for 24 Hour for settling time.

9 – Perform the cleaning cycle:

For each time ODME is stopped, we need start Cleaning cycle for ODME system. Have 2 wat to start: automatic or manual.

10 – Close the system

Once the ODME operation is completed, we can close all the valves and electric power. Pls remember to record into a Log book.


Pls read The ODME manual before use to avoid damaged system.

Some time, the oil is discharged via bypass system because they feel ODME to hard to operate. So pls know the equipment well, not only these will seem easy to operate but also will operate perfectly.

It is for protect our life also.


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