outlet means 16 fluid which enters second chamber 40 then moves through passageway 44 to outlet means 16 first internal chamber 34 may be considered to be an inlet chamber while second and third chambers 40 and 42 may also be referred to as outlet chambers seals 22 and 24 are seated in recesses of grooves in seal holding members 23 and 25 and are held in place respectively by annular flanges 27 and 29 of seal retainers 31 and 33 which are also carried by plunger 20 flanges 27 and 29 each compress or pinch a portion of their respective associated seals 22 and 24 and thus slightly reduce the radius of curvature of those seals in the areas which contact shoulders 28 and 30 when the valve is in the closed position this reduced radius results in a sharper or narrower line contact between the seals and the shoulders thereby resulting in a seal closing force which is spread over a somewhat smaller area thus affecting a higher load per unit area and accordingly a tighter seal for any given closing force retainer 31 also serves to maintain the proper axial spacing between the seals 22 and 24 to insure that they engage sealing shoulders 28 and 30 simultaneously as the valve assembly opens and closes various combinations of pressures balance one another as will now be described when the valve is closed as in fig2 and 2 a force f 2 tending to hold the valve closed is balanced by forces f 1 and f 3 all of these forces are factors of inlet pressure and the areas over which that pressure is applied thus the area related.