fall one half of the thread pitch the obturator 104 may be adjusted as necessary without removing the valve 100 from service or disconnecting flow lines the obturator 104 may be configured to translate vertically whenever the obturator 104 rotates independently of the extension 120 one or more bearings 126 may be disposed between the extension 120 and the base 118 to promote the rotation of the extension 120 when the obturator 104 rotates between the open and closed positions for example fig2 a and 2b show a trunnion 116 having a three piece bearing 126 with a disc shaped portion 126 a an elongate ring 126 b and a flat ring or washer 126 c the disc shaped portion 126 a of the bearing 126 may define an orifice therethrough to allow free rotation of the bearing 126 with the extension 120 the parts of the bearing 126 shown may be connected to one another or separate and one or more may be omitted entirely in some embodiments the bearing 126 may be integral with the base 118 or the extension 120 e g as surface coatings etc the bearing 126 may include any suitable material to allow rotation of the extension 120 such as metal plastic graphite e g grafoil u00ae a flexible seal made from graphite available from graftech int 39 l of lakewood ohio etc one or more lubricating materials may also be disposed between the base 118 and the extension 120 in some embodiments and as shown in fig1 the trunnion 116 may be integral with the valve body 102 in other embodiments the trunnion 116 may be a separate body secured to the valve body 102 e g by.