in the direction of flow through the valve an annular valve chamber 98 is formed between the housing 76 and the outer bladder sleeve 74 and this chamber 98 is connected to the pipe 38 which in turn is connected to the source of operating fluid under pressure 40 or vented or to a source of negative pressure as indicated by the arrow 44 the main passage 100 for material in the illustrated embodiment a slurry of fish extends axially through the valve 16 20 through the inner sleeve 72 thus the valve has concentrically positioned a central longitudinal passage 100 through the inside of sleeve 72 an annular expandible chamber 96 surrounding the sleeve 72 an annular outer sleeve 74 surrounding and providing the outer wall of the chamber 96 an annular expandible operating chamber 98 surrounding the outer sleeve 74 and an annular housing 76 surrounding and forming the outer wall of the chamber 98 the size of the apertures 96 and the total combined area of all the apertures are such that flow from the chamber 94 through the apertures into the passage 100 as indicated by the arrows 102 is normally slower than the flow of flushing fluid into the chamber 94 thereby causing the pressure to build in the chamber 94 and the chamber 94 to expand and force the inner sleeve 76 away from the outer sleeve 76 and into passage 100 as indicated by the arrows 104 to cause the passage 100 to constrict and tend to choke off flow therethrough before the valve is closed the rate of flow through the line 14 18 is significantly reduced or stopped the valve 52 is opened this may occur before flow through the line 14 18 has been slowed.