Separation time uses Stokes' Law — 200-micron average droplet, 100°F water viscosity (0.68 cP). Settling distance is the water column at 60% fill: bottom 90% of fluid depth. Hotter fluid separates faster. Colder fluid separates slower.
Assumes discrete droplets in a 50/50 oil-water mixture. Emulsified or chemically stabilized fluids will not separate gravitationally regardless of vessel size. Use with caution below 20° API — density contrast with water becomes minimal.
Ballpark estimates only. Not a substitute for engineering design or lab characterization.