The Type 523 Metering Ball Valve shall be true union and utilize a floating ball design.  An integrated index plate shall indicate stoke in degrees.  The ball shall be fully molded with a 180º tapered V-notch groove and shall be unidirectional indicated by flow direction arrows on the index plate.  The stem shall be blowout proof, utilizing a double o-ring seal and a predetermined breakpoint opposite the media side of the stem seals.  The seat carrier shall be adjustable and reverse threaded.  The handle shall double as a seat carrier adjustment or removal tool.  The valve nut threads shall be of buttress type.  Ball seats shall have an elastomeric backing o-ring and all elastomeric seals shall be of like material.  ANSI flanged versions shall meet the ANSI B16.5 150lb standard.  All valves shall be tested in accordance with ISO9393 and designed to ISO16135 standards.  All valves shall be manufactured under ISO9001 for Quality and ISO14001 for Environmental Management. Following assembly, every valve shall be certified bubble-tight exceeding Class VI standards.