Excess Sludge Formation in the Purifiers? Here is the First Aid!


One Important Test when the Purifier Suffers from Excess Sludge Formation.


Excessive sludge generation in purifiers are not very uncommon.  If you check with any ship’s engineer he might probably say that he spent half his on board tenure cleaning filters and removing sludge from purifiers.

A highly professional testing laboratory like Viswa Lab may have procedures and tools to find and mitigate excessive sludge generation; Whereas what are all the essential First Aid steps every engineer should be aware of to save the day when the ship experiences heavy sludge generation in the midst of a ocean.

When it comes to shipboard machinery operation, it is essential to keep the service tank full in such a way that the propulsion does not get impaired.  Thus, start the other purifier and run both the purifiers together such that:

  1. Feed is minimum.
  2. Temperature of fuel at the purifier inlet to be not less than 95 degree Celsius, if possible, do aim to maintain 98 degree Celsius.
  3. Optimum back pressure to maintain the interface (if ALCAP – this may not be applicable as it is controlled automatically).

Now, what to do with the sludge from the purifiers?

Can we diagnose something from it?

The answer to the above question, surprisingly, would be YES!

We can take a sludge sample and test it on board as well.

Are you worried that testing is a tedious job?

Don’t have to be concerned about the complexities of the testing.  These are not as extensive tests as those done by Viswa Lab in its laboratories.  The test is called as a simple BURN test, where the sample of sludge is subjected to open flame and the key is to observe what is happening to the outcome of the burn test.

Take the incriminated residue from the purifiers and heat them with an open flame.  This substance can be;

a. Sand and mud from bottom of the tank.  If this is the case, heating the debris will not make any change. Sand and mud will remain sand and mud.  Thus before the flame and after flame – the substance visual resemblance remains the same.

How to Mitigate: The only way to remove sand/mud is to Purify and filter out, and the filtered sludge should not be pumped back into the storage tanks.  Most ships, the fuel oil drain tank collects the discharged sludge from auto-filters and the same is being pumped back to the storage tanks. This has to be avoided.

b. It could be polypropylene type of plastic material.  When you heat this (90 to 100 deg C), it will melt, become a paste and freeze up again into a solid.

Exactly as may happen when you heat a piece of plastic. Usually, such debris will be slushy, somewhat soft and sometime hairy.  After this it will burn just like fuel.

How to Mitigate?: One of the two possibilities is to use an appropriate additive to condition the fuel. If this is not possible or this does not work well, then the only way is to blend the bad fuel with good fuel after checking the compatibility between both the fuels.

c. If the substance is soft and slushy and it is because of excess asphaltene in the fuel (may be due to unstable fuel), the debris when you heat it will burn just like fuel.

How to Mitigate: Most sludge dispersant type additives should work such that the asphaltenes molecules does not combine together to form a one big substance which clogs the filters.  Other possible way is to blend the bad fuel with the new good fuel after checking compatibility.

d. If the debris is from a contaminant such as DCPD or styrene, these are polymers.  When they are heated, they will soften and when you remove the heat, they will harden again.  This is exactly what happens under fuel pump conditions (150 deg C).

How to Mitigate?: The best way is to blend the bad fuel with good fuel after checking the compatibility between both the fuels.  When such blending is attempted – please contact or write to Viswa Lab for expert guidance.  The bad fuel should be proportionately in lower ratio when compared to the good fuel.

e. If the debris is soft and slushy and smells like rotten yoghurt it could be caused by Bacteria.

How to Mitigate?: Treating such bacterial or microbial infested fuel with biocides will help to certain extent.  The actual procedure for dosing biocide and further treatment is not the scope of this write-up.

Some images during Burn Test:



  1. All fuel blending has to be carried out under strict expert guidance and after checking compatibility between the two fuels.
  2. All additives may not mitigate the problem.  The effectiveness of additives may vary and for further information, please do not hesitate to write to Viswa Lab or write to us at [email protected]
  3. If none of the above methods work, it is recommended to de-bunker the fuel for the safety of the ship and the engines.
  4. Take care when you attempt a burn test.  Consider all safety precautions before you attempt with necessary risk assessments.

We thank Viswa Lab for sharing some images and videos which would definitely be beneficial for the shipboard engineers who suffer from fuel related problems.

Read Further – 14 Critical Points to know When You Co-mingle (blend) Two Fuels

Disclaimer: This video is intended for informational purpose only.  This may not be construed as a news item or advice of any sort.  Please consult the experts in that field for the authenticity of the presentations.

Reference: Aderco