The amount of free open area is the ratio of the open area through the strainer basket to the cross section area of the pipe.
A common term used in strainer design is “Open Area Ratio.” OAR equals the total open basket area divided by the internal cross-section area of the inlet pipe. It is a measure of relative debris holding capacity and is usually 1 to 4 times the inlet pipe area.
Open Area Ratio = Total Basket Element Open Area / Inlet Pipe Cross Sectional Area (in. squared).
