after design the separator according to API 12J, give the oil dimension,such as 500μm,than I can find the suitable size of the separator,but the client want to achieve the target,such as the water in oil is no more than 20v%, or the oil in the water is no more than 500ppm, so, what is the relationship between the oil dimension and the client target,I do not know, this is an experience? could someone help me?