Boundary condition
 

Hi,
I'm trying to simulate a two phase separator vessel (water& oil). I need to maintain an interface level for oil and water in vessel. there are one inlet Boundary condition as mass flow rate and i need two BCs for outlets. Oil outlet is at top of the vessel and water outlet at bottom. vessel operating pressure is 10bar, so for oil outlet BC, i set static pressure 10bar and for water outlet BC 10bar+hydrostatic head(oil+water) above the water outlet. i set initial conditions to have interface level at the required height. but solver stops after few iterations with an overflow error.
I really don't know what to do, everything looks logical but it is not even running....