Hi all,
Hijacking the thread a little. Most utilities/mining/industrial I have worked with over the years have had a rock filled, closed base concrete bund around their transformers. The bund is sized to hold (selected and maintained) rocks, plus all oil, plus storm (and sometimes fire) water. It is considered that any fire will be suppressed by the rocks and oil released will not cause a pool fire. I know of some examples that support that - windings and oil left in the tank burned for many hours despite attempts at extinguishing (no Sergi!), but oil in the bund did not.
My new utility instead uses a shallow bund, piped into a below-ground tank sized to hold full oil volume. An underflow from this tank goes to the top of a second, identical tank, and an underflow from that tank via a valve to waste at grade. Oil floats, so any oil stays in the first tank, with any rain water underflowing to the next tank. Normally the water in the next tank is tested before release and any small amounts of carryover oil pumped out via hatch for disposal.
The pipe from the bund is taken from a small sump. Standards say that this should have a "suitable" flame trap. We are electrical folk, unsure what is suitable, and have been unable to find or buy any advice. Does anyone have any pointers?
Many thanks,
John.