Variable pressure reducing device

Abstract

A variable pressure reducing device for reducing high pressure in steam and hot water samples forces the liquid through an annular passageway between a pair of rods within a complementary pair of tubes. The flow rate through the rod-in-tube device, or the pressure drop across the device, is adjustable by means of a rotatable guide screw for adjusting the position of the rods within the tubes. The rods are tapered to provide a smooth flow of liquid through the device. The seal around the guide screw is self energized by means of a seal jacket between a valve gland and a stem portion of the guide screw constructed so that the biasing force of a spring on the seal jacket is supplemented by pressure from liquid flowing through the device The guide screw is centered within the valve gland to keep the guide screw properly aligned, particularly when the device is used with a motor for rotating the guide screw to adjust the position of the rods.

We claim as our invention:  
     
       1. A variable pressure reducing device comprising: 
       a barrel;  
       a pair of tubes joined to one end of the barrel;  
       a pair of rods adjustably insertable within the tubes with each rod having a relatively wide diameter at an upper end of the rod, a relatively narrow diameter at a lower end of the rod, and a smooth tapered outer surface extending from the upper end to the lower end;  
       a rotatable guide screw and complementary threaded ring within the barrel for adjusting the rods;  
       a valve gland, including an internal annular ridge seat with a central opening therein, placed over the other end of the barrel;  
       the threaded guide screw having an annular shoulder complementary to the ridge seat and having a stem portion projecting through the central opening of the gland;  
       a low friction thrust washer between the shoulder of the guide screw and the ridge seat of the gland;  
       an annular seal jacket between the stem portion of the guide screw and an inner wall of the gland;  
       a spring for biasing an inner wall portion of the jacket against the stem portion of the guide screw and for biasing an outer wall portion of the jacket against the inner wall of the gland;  
       a back-up washer abutting against the seal jacket;  
       annular centering means for centering the stem portion of the guide screw within the gland; and  
       a nut with a central opening placed over the stem portion of the guide screw and threaded over the gland.  
     
     
       2. The variable pressure reducing device according to claim  1 , wherein the centering means comprises a bearing and washer. 
     
     
       3. The variable pressure reducing device according to claim  1 , wherein the centering means comprises a bushing. 
     
     
       4. The variable pressure reducing device according to claim  1  further comprising a motor for rotating the guide screw to adjust the position of the rods within the tubes. 
     
     
       5. The variable pressure reducing device according to claim  1 , wherein pressure from liquid flowing through the device further presses the seal jacket against the guide screw and gland wall. 
     
     
       6. A variable pressure reducing device for reducing high pressure of liquids comprising: 
       a pair of rods adjustably insertable within a complementary pair of tubes by means of a rotatable guide screw;  
       each rod having a smooth outer surface tapered from a relatively wide diameter at an upper end of the rod down to a relatively narrow diameter at a rounded lower end of the rod;  
       the guide screw being held within a barrel by a valve gland;  
       a seal jacket within an annular space formed by the outer diameter of a stem portion of the guide screw and the inner diameter of a wall of the gland;  
       a spring for biasing an inner wall section of the seal jacket against the stem portion of the guide screw and for biasing an outer wall section of the seal jacket against the gland wall;  
       a washer abutting the seal jacket; and,  
       centering means for centering the stem portion of the guide screw within the gland.  
     
     
       7. The variable pressure reducing device according to claim  6 , wherein the guide screw is held within the barrel by the valve gland by means of an annular ridge seat within the gland, a complementary annular shoulder on the guide screw, and a thrust washer between the shoulder and ridge seat. 
     
     
       8. The variable pressure reducing device according to claim  8 , wherein the centering means comprises a bearing and washer. 
     
     
       9. The variable pressure reducing device according to claim  8 , further comprising a belt drive motor for rotating the guide screw to adjust the position of the rods within the tubes. 
     
     
       10. The variable pressure reducing device according to claim  7 , wherein the centering means comprises a bushing. 
     
     
       11. The variable pressure reducing device according to claim  10 , further comprising a direct drive motor for rotating the guide screw to adjust the position of the rods within the tubes. 
     
     
       12. An improved variable pressure reducing device of the type which includes a pair of tubes joined to one end of a barrel, a complementary pair of rods adjustably connected to a threaded ring on a rotatable threaded guide screw within the barrel, the pair of rods being insertable within the pair of tubes, respectively, thereby forming a passageway between the outer diameter of the rods and the inner diameter of the tubes for fluid to flow therethrough, the improvement comprising tapering the rods with a smooth outer surface from a relatively wide diameter at an upper end of the rod which is connected to the threaded ring down to a relatively narrow diameter at an opposite rounded end of the rod to form a progressively narrower annular passageway to smooth the flow of fluid therepast. 
     
     
       13. The improved variable pressure reducing device according to claim  12 , further comprising an improvement in the sealing means of the device comprising: 
       a valve gland on the other end of the barrel including an internal annular ridge seat and a central opening therein;  
       the guide screw having an annular shoulder complementary to the ridge seat and a stem portion projecting through the central opening of the gland;  
       a low friction thrust washer between the shoulder of the guide screw and the ridge seat of the gland;  
       a seal jacket in an annular space formed by the inner diameter of a wall of the gland and the outer diameter of the stem portion of the guide screw;  
       a spring for biasing the seal jacket against the wall of the gland and the stem portion of the guide screw;  
       a washer abutting the seal jacket;  
       centering means for centering the guide screw; and,  
       a nut over the open end of the annular space in the gland.  
     
     
       14. The variable pressure reducing device according to claim  13 , wherein the centering means comprises a bearing and washer. 
     
     
       15. The variable pressure reducing device according to claim  13 , wherein the centering means comprises a bushing. 
     
     
       16. The variable pressure reducing device according to claim  13 , wherein pressure from liquid flowing through the device further presses the seal jacket against the guide screw and gland. 
     
     
       17. The variable pressure reducing device according to claim  16 , further comprising a motor connected to the stem portion of the guide screw for motorized adjustment of the position of the rods within the tubes. 
     
     
       18. A variable pressure reducing device for reducing high pressure in steam and liquid sampling lines, said device comprising: 
       
         at least one tube forming at least one elongate passageway, wherein said at least one elongate passageway has an inlet end for receiving fluid at an elevated first pressure and an exit end for discharging fluid at a second pressure lower than said elevated pressure;  
       
       
         at least one elongate rod mounted for movement in said at least one elongate passageway, wherein said at least one elongate rod has a first end and a second end such that said at least one elongate rod is smoothly tapered from said first end to said second end for providing a substantial pressure loss therealong;  
       
       
         an adjustment mechanism for moving said at least one elongate rod into and out of said at least one elongate passageway, wherein said adjustment mechanism is connected to said first end of said at least one elongate rod; and  
       
       
         an annular gap between said at least one elongate rod and said at least one elongate tube wherein said annular gap becomes progressively narrower along said at least one elongate rod in a linear direction from said first end of said at least one elongate rod to said second end of said at least one elongate rod.  
       
     
     
       19. The device of claim  18  wherein said at least one elongate rod tapers from said first end to said second end.  
     
     
       20. A variable pressure reducing device for reducing high pressure in steam and liquid sampling lines, said device comprising: 
       
         first and second elongate passageways;  
       
       
         first and second elongate rods extending along said first and second passageways, respectively, wherein each rod of said first and second elongate rods has a length and a first end and a second end such that at least said first rod is free of a step and therefore smoothly tapered along a length from a relatively wide diameter at said first end to a relatively narrow diameter at said second end; and  
       
       
         first and second separate annular gaps between each passageway of said first and second elongate passageways and said first and second elongate rods extending therealong, respectively, wherein each gap of said first and second separate annular gaps has a linear, unstepped outer boundary along said length of said first and second elongate rods, respectively, such that fluid pressure decreases along said first passageway from said relatively narrow diameter of said second end of said first rod to said relatively wide diameter of said first end of said first rod.  
       
     
     
       21. The device of claim  20  wherein a diameter of each gap of said first and second separate annular gaps changes along a length of each gap of said first and second separate annular gaps.