Gravity Separation Velocity Calculation


The gravity force is commonly used in oil treating equipment to separate the water from the oil in continues phase; the water droplet tends to separate from the oil since it’s heavier than the oil. The separation speed is limited by the drag force caused by the water movement through the oil; the constant velocity is reached when the gravity force and the drag force are equal. We can compute it Stokes’ Law:

From the equation we can conclude:
1. The larger water droplet in oil will result in more easier to treat since it will have move velocity and can be settled faster.
2. More lighter crude will easier to treat since it has more difference in density between the water droplet and the oil phase.
3. More higher oil temperature will easier to treat since it has low viscosity resulting in greater downward velocity.


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