1) What is ODME?
O.D.M.E is Oil Discharge Monitoring Equipment which is used to check and monitor oil is discharged follow related rule ( MARPOL 73/78 ) when a tanker discharges the sea water from the slop tank where sea water used to clean the tanker after unloading the cargo to be prepared to ship other kind of cargo has been stored.
“Oil” means all kinds of oil including crude oil, heavy oil, sludge, waste oil and refined oil.
ODME is to remove water from the slops and not as much oil as is allowed also.
2) Condition to discharge oil into sea:
3) ODME Components:
The formula for Instantaneous rate of discharge:
ODME need to measure IRD, it needs values:
- Oil content in PPM
- Flow rate.
- Speed connection is usually given either from log or GPS.
The computing unit of the ODME will show all these above values in Cargo control room.
How does it get these value?
a) Flow rate / Flow meter: it is items 5 in sketch.
ODME computing unit gets the flow rate from flow meter. A small sample line goes from the main line, pass through the flow meter and goes back to the main line. Flow meter calculates the flow in m3/Hr and gives this value to the computing unit through a signal cable.
b) Measuring PPM: it is Analysing unit
The measuring principle relies upon the fact that different liquids have different light scattering characterstics. Based on the light scattering pattern of oil, measuring cell determines the oil content.
We measure PPM in a water sample ( The sample water is passed through a quartz glass tube ), a sample from the discharge water need to pass through the measuring unit. This job is done by a sample pump. Sample pump will take the sample from the discharge line before the discharge valves. This sample is sent to the analysing unit for measuring the oil content and then sent back into the same discharge line.
This pump is protected by a pressure sensor is fitted inside the analysing unit. This pressure sensor measures the inlet and outlet pressure of the sample pump.
The measuring unit need to be cleaned during the operation. This is to avoid measuring unit will get wrong readings. To clean the measuring unit, the fresh water will be use for flushing.
The computing unit calculates IRD:
- IRD is less than 30 L/NM, it gives the command to solenoid valve assembly to open the overboard valve and close slop recirculation valve.
- When the IRD becomes more than 30 L/NM, it closes the overboard valve.
The computing unit also calculates the amount of actual oil that has been discharged to sea to make sure oil not more than 1/30000 of the total cargo carried. Before we start ODME, we need to calculate and feed this maximum allowed value in the ODME.
Now you already know how ODME is made up of and components of ODME, lets see how crew should operate ODME???