The only information available for the effects of API gravity difference on blend time comes from a design procedure for propeller side-entering mixers.  However, the flow patterns developed by propeller mixers and jet mixers are similar, because both involve the expansion of free jets.  The amount of time required to blend crudes with different API densities depends on several factors, but for simplicity a relative time factor can be applied to a known time for another density difference.  The time factor as a function of API density difference is shown in the attached graph.

The better method of reducing the effect of density difference is to add the new crude near the jet mixer and avoid initial stratification.  Any stratification can be difficult to overcome, since the density interface must first be broken before blending can begin.

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