moves downward the movement of piston 41 sets the packoff seal 45 between an outer portion of casing hanger 39 and the inner diameter of the subsea wellhead housing referring to fig4 once the piston 41 is driven downward and packoff seal 45 is set the stem 13 is then rotated four additional revolutions in the same direction as the stem 13 is rotated relative to the body 25 the stem 13 moves further longitudinally downward relative to body 25 and casing hanger 39 stem 13 also moves downward at this point relative to piston 41 as the stem 13 moves longitudinally stem ports 15 17 and body ports 33 35 also move relative to one another lower stem port 17 aligns with lower body port 35 allowing fluid communication from the axial passage 14 of stem 13 through stem 13 into and through body 25 and into an isolated volume above packoff seal 45 upper stem port 15 is still aligned with upper body port 33 the latch device located with the slot 32 on the outer sleeve 30 is activated by the movement of the stem 13 and will act in conjunction with piston locking ring 43 to restrict the upward movement of piston 41 beyond the latch device pressure is applied down the drill pipe and travels through the axial passage 14 of stem 13 before passing.