is being pumped in a forward direction as illustrated by lines 27 on fig2 it encounters a first member 12 hereinafter referred to as a poppet poppet 12 is concentrically located within the tubular body 13 and shares the same central axis 49 with a second element 11 hereinafter referred to as a closure element making poppet 12 and closure element 11 concentric with one another as the fluid passes poppet 12 it encounters closure element 11 closure element 11 is urged longitudinally toward poppet 12 via closure element spring 14 thereby resisting movement until such time as the differential pressure of the fluid exceeds the spring force of the closure element spring 14 poppet 12 is urged longitudinally toward the closure element 11 via poppet spring 15 closure element 11 and poppet 12 are permitted to travel independently of one another along their central axis 49 closure element 11 and poppet 12 abut at 23 closure element 11 is sealed to the internal bore surface 47 of body 13 via sealing element 19 sealing element 20 forms a seal between the closure element limiting structure 16 and the outside diameter 51 of closure element 11 poppet spring 15 is held in place via retaining device 18 retaining device 18 is illustrated as a snap ring retaining device 18 may be of various forms such as threaded sleeves press.