Over Flow Sights are used in oil lines to allow visual observation of the flow and clarity of the oil.  They are often used on large ring oil or reservoir type bearings of steam turbines or gear boxes, but can be used for many other applications.  Over Flow Sights are used with low pressure.  The liquid flows upward through the bottom inlet, over the center stand pipe, and exits the sight through a side outlet. The chamber is vented with a cap nut.