Separator for separating a heavier liquid from a lighter liquid

A separator for separating a heavier liquid from a lighter liquid that floats on the heavier liquid, the separator comprising a casing having an inlet for a mixture of lighter and heavier liquids, a first outlet for the lighter liquid the first outlet in use of the separator being connected to a suction pump for selectively changing the conditions in the casing by reducing pressure within the casing below atmospheric so that lighter liquid is drawn from the casing through the first outlet and a second outlet for the heavier liquid, the second outlet being at a lower end of said casing so that the heavier liquid which has accumulated in the lower end of said casing can be discharged there through, a float structure including a float which floats on the heaver liquid and sinks in the lighter liquid, the float structure further including closure means which has a first position in which it shuts-off said second outlet and a second position in which said second outlet is open and heavier liquid flows from the casing through the second outlet, the float when lifted by an accumulation of heavier liquid in said casing displacing the closure means from its first position to its second position, and forcing means responsive to the change in conditions that occurs in the casing when suction is applied to said first outlet and which exerts a force on said closure means during that period during which lighter liquid is being drawn from said casing through said first outlet, said force holding said closure means in said first position while the pressure in the casing is below atmospheric.