oil filtration of transformer

Precaution? Read the manufacturer's instructions.

paliwwal,

First things first...

De-energize the transformer!!! (Lock-out/Tag-out).

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OK, now that we've gotten that out of the way...

You say you erected the transformer, When? (How old is the transformer? )

Has the dielectric oil ever been tested for Polychlorinated Biphenyl (PCB) content, or is the transformer labeled/certified as being non-PCB equipment?

Here in the USA, PCBs were banned by the EPA for most uses (including most transformer applications) approx. 30 years ago. However, I don't know where in the world you are, and whether there are any similar regulations there...

If PCBs are potentially an issue, I'd suggest you review some background information on the subject at the following web sites:

http://www.cdc.gov/niosh/npg/npgd0125.html

http://www.epa.gov/pcb/pubs/about.htm

http://www.epa.gov/pcbs/pubs/manual.pdf

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Just my $0.02...

Can we start by determining why you need to filter the oil? Newish transformers should not require any filtering. What tests have you done? Do you want to remove carbon after bushing failure, or is sit the on-line tap changer oil that must be cleaned, do you have high moisture, or acidity or sludge problems? Some of these require different solutions with different precautions.