How to Settle Tanks for Crude Oil Emulsions

Crude oil contains contaminants called emulsions that make the oil unusable in its raw form. The oil refining industry has developed methods for removing those contaminants. Methods continue to evolve, and new ways to measure the emulsions in oil have made it possible to be more precise when calculating the thickness of the non-oil layers in settling tanks. Traditional methods assumed there was a clear line between the layers in a settling tank, when in reality there is a gradual tapering off of purity between emulsions and oil. Learn new methods used in settling tanks.

Things You'll Need

• Mass tank gauge

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Instructions

• 1

  Place crude oil in a settling tank. Allow it to sit undisturbed for days, but do not leave it for more than a week. Gravity will separate the tank contents into levels of water, emulsions and oil.

• 2

  Measure the thickness of the layers in the tank. Traditionally, this has been done with hand probes inserted through the top of the settling tank. This method resulted in rough estimates that showed water levels from a few inches to 4 feet and emulsion levels of up to 10 feet and sometimes even 20 feet. You can use a gauge instead. A mass tank gauge inserted through a flange in the top of the tank gives you a precise reading of oil, emulsions and water percentages, including the percentages in transitional areas as the gauge moves between layers.

• 3

  Drain water with a water bleed-off valve located near the bottom of the tank. This valve shuts off when the drained fluid shows significant amounts of oil.

• 4

  Measure the mixture that remains in the settling tank. Note the thickness of the emulsion level and the oil level.

• 5

  Pump out the oil down to where the emulsion level begins.

• 6

  Pump out the emulsions to be discarded or processed for usable by-products.

• 7

  Clean the settling tank thoroughly, including the floating floor.