Patent Number: 047050713
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 there is shown a steam control valve 10 for a power plant steam chest 12. The steam chest 12 includes a hollow elongated central member 14. Central member 14 has a steam inlet means 16 passing therethrough in predetermined position as shown in FIG. 1. The central member 14 also has a steam outlet means 18 passing therethrough in predetermined position. Steam inlet means is at a relatively higher pressure than the steam outlet means. For example the pressure at the steam inlet 16 may be 1000 psia and the pressure at the steam outlet 18 200 psia, for example. In a nuclear power plant the throttle valve controls the flow of steam from the steam generator to the steam chest as is known in the art. The central member has control valve aperture means 22 passing therethrough in predetermined position. The control valve 10 includes a cylindrical outer housing means 24 having a lip member 26 affixed to the upper end 28 thereof. The lip member 26 has an outside diameter such as 40 inches which is greater than the control valve aperture 22 which typically has a diameter of 25 inches. The outer housing 24 passes through the control valve aperture and is maintained in predetermined position by the lip member 26. The outer housing 24 includes a bottom muffler portion 30. The bottom muffler portion 30 has eight window opening means therethrough 32 of predetermined dimensions such as 9.times.6.5 and spaced about the circumference of the bottom muffler portion. The bottoms 34 of the window openings 32 are a predetermined distance such as 4.0 inches above the bottom 36 of the bottom muffler portion 30. The bottom muffler portion 30 of the outer housing 24 has an initial inside diameter such as 20 inches which is greater than the final inside diameter which is 19.4 inches of the remaining portion of the outer housing 24 above the muffler portion. A movable plug 38 is provided for controllably sealing the high pressure inlet means 16 from the relatively low pressure outlet means 18 as is known in the art. The movable plug 38 is coaxially aligned with the outer housing 24 and is slidable within the interior 40 of the outer housing. Shaft means 42 for moving the plug is provided as is known in the art. The shaft means 42 for moving the plug is affixed at one end 41a to the plug in predetermined position as shown in FIGS. 1 and 2. The shaft means 42 is affixed at the other end 41b to lifting means 43 which is conventional. The plug 38 preferably has groove means 44 therein about the circumference thereof in predetermined position as shown in FIG. 2. Circular seal ring means 46 is provided preferably split pressure rings. The circular seal ring means 46 is sized to be insertable into the groove means. The steam control valve 10 is described thus far as conventional. The improvement comprises a bottom ring portion 48. The prior art bottom ring portion is shown in FIGS. 2 and 3. As discussed previously the bottom ring portion of the prior art comprised a plurality of flowholes 49 disposed therethrough and upper band 51 without flowholes adjacent the window openings. The bottom ring portion of the present invention is shown in FIGS. 4-8. The bottom ring portion 48 of the present invention has a plurality of pockets 50 therein about the inner circumference 52 thereof. Each of the tapered pockets 50 is of predetermined dimensions such as about 5 inches wide, 3.8 inches high and 1.8 inches deep at the top of the ring. Each of the pockets is aligned with one of the window openings 32. As shown in FIG. 6 each of the pockets 50 has a steam exit portion 52 having an initial central diameter 54 substantially equal to the inside diameter of the bottom muffler portion 30 of the outer housing 24. Each of the pockets 50 has a final central diameter 56 at the steam entrance portion 58 of the pocket 50 a predetermined amount larger than the initial central diameter of the steam exit portion 30 of the outer housing 24 with the steam entrance portion 58 of each of the pockets 50 being disposed with in bottom 34 of the aligned window openings 32. The exit portion 52 of the pocket 50 being a predetermined distance such as 0.20 inches above the bottom of the outer housing 24. A channel 60 is provided at the bottom of the muffler portion for engaging said central member 14 as shown in FIGS. 5 and 6 in the same manner as in the prior art. With reference to FIGS. 4 and 5 utilizing the present invention when the plug 38 is initially lifted by the lifting means 43, steam at the high pressure inlet 16 flows through the window openings 32 and through the pockets 50. As the plug is raised the steam flow through the pockets is increased without damaging vibration of the outer housing means and plug. Preferably the wall portion 62 of the ring portion 48 from the entrance portion 58 to the exit portion 52 of each of the pockets is offset from the vertical. The entrance portion 58 to the exit portion 52 is typically at an angle offset 26.degree. from the vertical as shown in FIG. 6. Preferably the side portions 64 of the ring portion 48 proximate said pockets have a predetermined curvature such as a 1.25 inches radius.