One of the most common problems faced by marine engineers during purifier operation is oil coming out through the water outlet. Instead of only water and sludge, valuable fuel oil starts flowing to the drain tank. This not only wastes fuel but also indicates that the purifier is not separating properly.
How Do You Identify Oil Loss?
During watch, you may notice:
- Oil visible in water discharge line
- Oily drain tank or sludge tank
- Increase in sludge tank level
- Fuel consumption higher than normal
- Cloudy or unstable discharge
If you see any of these signs, the purifier interface is disturbed and immediate action is required.
Main Causes of Oil Loss Through Water Outlet
1. Wrong Gravity Disc Size (Most Common Cause)
The gravity disc controls the oil–water interface inside the bowl. If the disc size is too large, the interface shifts outward and oil escapes through the water outlet.
Symptoms:
- Continuous oil in water line
- Stable but wrong discharge
Solution:
- Check fuel density
- Refer to maker’s gravity disc chart
- Fit correct smaller size disc
This single mistake causes most oil losses onboard.
2. Low Fuel Temperature
If fuel is not heated properly, viscosity remains high. Thick oil cannot separate easily from water, causing improper interface formation.
Symptoms:
- Poor separation
- Water mixed with oil
- Oil carryover
Solution:
- Maintain temperature around 98–104°C
- Check heater operation
- Ensure steam supply is proper
3. Excessive Throughput (High Flow Rate)
When oil feed rate is too high, the oil does not stay inside the bowl long enough for separation. As a result, oil and water mix and escape together.
Symptoms:
- Overflowing discharge
- Unstable interface
Solution:
- Reduce feed rate
- Follow maker’s rated capacity
4. Dirty or Blocked Disc Stack
Sludge deposits between discs restrict proper oil flow. Separation area reduces and oil moves with water.
Symptoms:
- Reduced efficiency
- Frequent oil contamination
Solution:
- Stop purifier
- Clean disc stack thoroughly
- Remove sludge deposits
5. Improper Sealing Water Supply
Sealing water forms the initial water ring inside the bowl. Without proper sealing water, the interface cannot stabilize.
Symptoms:
- Oil immediately appearing in water outlet after start
Solution:
- Ensure sealing water line is open
- Check solenoid valves
- Confirm adequate pressure
6. Worn Seals or Internal Leakage
Damaged O-rings or worn seals inside the bowl may allow internal mixing of oil and water.
Symptoms:
- oil loss even after adjustments
- Leakage inside bowl
Solution:
- Inspect seals during overhaul
- Replace worn O-rings
Troubleshooting Sequence
If oil loss happens during your watch, follow this order:
- Check temperature first
- Reduce throughput
- Verify gravity disc size
- Check sealing water
- Plan cleaning of disc stack
Usually the problem gets solved within these steps.
Preventive measure
- Always heat fuel to correct temperature before entry
- Select gravity disc based on fuel density change
- Clean bowl weekly
- Monitor discharge clarity every watch
- Never overload purifier capacity
Good watchkeeping prevents most oil loss problems.