The Displacement type separator, after the initial water fill, is ready to receive a product spill.
Note optional disposal of water effluent by gravity flow or by pumping.

The Displacement type separator is illustrated after sufficient oil has accumulated to produce an equilibrium resulting from the weight differential of the oil-water mixture in the separation chamber, and the water in the water holding sump. Subsequent additions of either oil or water will displace like amounts into either the oil or water sump. The "last-in, last-out" operation allows full utilization of the time interval between spills for gravity separation.

The patented design allows catastrophic release of oil to be contained in the separator. Once the dedicated oil sump is full, the oil spill depresses the water ballast in the separation chamber. Since the weight of the oil cannot overcome the weight of the water in the transfer pipe, the vessel hydraulically "locks-up" containing the spill and preventing a release to the environment.