Ship was being sold for scrap and was required to be delivered gas free.
1st step is washing tanks using heated sea water through the machines while keeping the inert gas on the tanks.
2nd step is once all of the tanks were washed and empty hydro carbon vapors are purged by replacing the gas in the tank with fresh inert gas until there is zero LEL found
3rd step is purging the inert gas with fresh air so men may enter.
4th and final is checks by a certified marine chemist that the tank is free of any explosive vapors and oxygen content is safe for men to enter.
In total this process took about 5 days. Had the ship not been going to scrap the sludge in the tanks would have been removed by men entering and shoveling into buckets. It was estimated there was 300, 55 gallon drums of sludge in the tanks. Tank capacity about 860,000 barrels
