API Spec 1590 pdf download.SPECIFICATIONS AND QUALIFICATION PROCEDURES FOR AVIATION FUEL MICROFILTERS 3.1.3 Flow rate Elements with a nominal 150 mm (nominal 6 in.) outside diameter shall meet the performance specification at a minimum flow rate of 10 l/sec/m of effective media length (equivalent to 6 l/min/cm or approximately 4 US Gal./min/in). Manufacturers may qualify elements at higher flow rates...