The IEC standards tell that if Acidity and dessipation factor have high values, we should conduct test for sludge and sediments. My question is if we find out that adequate amount of sludge is present in transformer oil and precipatations, what can we do ?
How to remove these sludge and sediments ?

Faisal,

You can contact one of the many firms that specialize in transformer oil cleanup. They can usually put you in contact with a local presence.

Alan

There are on line on site transformer oil regeneration machines available, which should be able to do the job.

Taking away the sediments is easy, the question is why are these sediments in Oil. Before making a filtration take a sample of oil and send to a laboratory for DGA (Dissolved Gas Analysis) and find out what is going on. And correct the problem.

Besides, I am in Africa right now, and everybody says that here things are not done as in America. Transformers are the same everywhere and must be taking into account seriously. Maybe sludge and sediments are by the careless way your contractors manage and fill transformers. See Std. ASTM D3487-81. Nothing personal.

The Oil regeneration plant is the solution for your problem, Oil regeneration plant is used to bring back the oil quality to the pure form.