Separators, as the name implies, provide a means of separating vapor from liquid. This process is usually performed under a controlled vacuum to reduce the boiling point. The vapor/liquid mixture enters through the side of the separator in such a way as to promote swirling. This swirling action provides a means to release vapors from droplets. These vapors are drawn off leaving the droplets to collect in the bottom of the separator.

two pictures of separators
picture of separator