30 which pivots from open to closed positions with shaft 40 within cylindrical passageway 20 having axis 50 shaft 40 is connected to exterior control means not shown in figures such that rotation of shaft 40 opens and closes movable valve member 30 having peripheral valve sealing surfaces 31 thereon the use of a butterfly valve assembly with the present invention is shown only by way of example any valving member including a ball valve which is retained within passageway 20 and is pivotal about an axis transverse to central passageway axis 50 between an open a closed fluid passage position may be so employed a firesafe sealing means utilizing the present invention is shown generally at 90 in fig1 and is illustrated in detail in fig2 annular groove means 80 is disposed in passageway 20 in radial alignment with peripheral valve sealing surface 31 of movable valve member 30 when movable valve member 30 is in a closed position groove means 80 is formed of a recess between valve body 10 and retainer means 60 groove means 80 is provided with axially extending groove shoulder means 81 radially inward from first groove portion or cavity 82 first groove portion or cavity 82 is likewise radially inward from second groove portion or cavity 83 radial extension 85 of groove means 80 extends radially outward from second groove portion 83 the.