BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of an exemplary embodiment of a typical subsurface safety valve with integrated flapper mount, hard seat and soft seat seal with tabbed soft seal retaining ring.
FIG. 2 is a sectional view of an exemplary embodiment of a typical subsurface safety valve with integrated flapper mount, hard seat, and soft seat seal with tabbed retaining ring.
FIG. 3 is another sectional view of an exemplary embodiment of a typical subsurface safety valve with integrated flapper mount, hard seat and soft seat seal with tabbed retaining ring.
FIG. 4 is an isometric assembled view of an exemplary embodiment of a typical subsurface safety valve with integrated flapper mount, hard seat, and soft seat seal.
FIG. 5 is an isometric exploded view of an exemplary embodiment of a typical subsurface safety valve with integrated flapper mount, hard seat and soft seat seal with tabbed soft seal retaining ring showing either roll pins or set screws to restrain further movement of the retainer ring upon assembly.
DETAILED DESCRIPTION
Referring in particular to FIG. 2, flapper 10 mounts to hinge posts 20 that protrude from the bottom of the spring housing 30 so that the flapper 10 becomes part of the spring housing 30. A conical surface area (hard seat) 40 annularly surrounding the main bore 50 of the safety valve and protruding from the bottom of the spring housing 30 creates a metal-to-metal contact surface 60 with the flapper 10 when the flapper 10 is in the closed position, as shown in the figure. A non-metal sealing ring 70, or soft seat, installs around the conical surface 40 and is retained in place on the bottom side of the spring housing 30 by a retainer ring 80. Now referring to FIGS. 3 and 5, the outer parts of the retainer ring 80 contain tabs 90 that fit into mating slots 100 milled into the bottom of the housing 30. The tabs 90 insert into the mating slots 100, and, when the retainer ring 80 is rotated, slide into grooves 110 adjacent to the mating slots 100 to prevent the retainer ring 80 from slipping off of the spring housing 30. Two roll pins or set screws 120 insert into two holes 130 on the outer, annular surface of the spring housing 30 and protrude into the groove 110 on each side of at least one tab 90 to immobilize it within the groove 110 to prevent the retainer ring 80 from inadvertently rotating back off of the housing 30. The retainer ring 80 contains slots “castellations” 140 that facilitate rotation by an installation tool (not shown) during assembly.
Referring to FIG. 2, in one embodiment, the soft seat seal 70 fits around the outer side of the conical surface 40 and has a flanged upper end 150 that contacts the bottom side of the spring housing 30 when the seal is pushed up the conical surface 40 by the closing of the flapper 10. The flanged end 150 fits inside a circular, milled slot 160 (FIG. 5) on the bottom side of the spring housing 30. By design, the milled slot 160 (FIG. 5) is larger than the flanged end 150 so that when the soft seat seal 70 installs onto the conical surface 40, the flanged end 150 of the seal 70 does not initially contact the bottom side of the housing 30 or the outer diameter surface of the circular, milled slot 160. When the flapper 10 pivots closed and pressure builds up underneath the flapper 10, the flapper 10 pushes the soft seat seal 70 up the conical surface 40. The gap 170 between the flanged end 150 of the seal 70 and the bottom side of the housing 30 allows the soft seat seal 70 to move upwards without compressing the seal. The soft seat seal 70 material stretches as it slides up the ever-increasing diameter of the conical surface 40, building up energy within the material. When the flapper 10 is opened, the energy stored in the soft seat material releases, causing the soft seat seal 70 to move back up the conical surface 40 to its original position. During opening and closing of the flapper 10, the soft seat seal 70 is not compressed because of its movement along the conical surface 40 and does not get damaged due to compression. Nor is the soft seat seal 70 at risk of a compression set due to repeated openings and closings of the flapper 10.
Referring now to FIGS. 2 and 5, the soft seat seal 10 also contains one or more notches 180 along the perimeter of the upper flanged end 150 of the seal 70. When the flapper 10 closes and the soft seat seal 70 is pushed up the conical surface 40, if the gap 170 did not exist between the bottom of the spring housing 30 and the upper flanged end 150 of the soft seat seal 70, the upper flanged end 150 would tend to buckle, thereby opening a gap where gases, such as nitrogen, may get trapped between. When the gas pressures are rapidly bled from below the closed flapper 10 the gases trapped between spring housing 30 and the upper flanged end 150 of the soft seat seal 70 would rush past the seal, deform it, and cause damage to the soft seat material. The gap 170 between the flanged end 150 of the seal 70 and the annular outer surface of the circular milled slot 160, along with the notches 180 along the perimeter of the flanged end 150 of the seal 70, provide a release path for trapped gases, thereby reducing or eliminating the damaging effect of trapped gases behind the seal.
The soft seat material may be made of any suitable elastomeric or non-elastomeric material such as Teflon®. The retaining ring is made of a metallic material that conforms with the requirements of NACE MR0175.
It will be apparent to one of skill in the art that described herein is a novel method and apparatus for sealing a subsurface valve. While the invention has been described with references to specific preferred and exemplary embodiments, it is not limited to these embodiments. The invention may be modified or varied in many ways and such modifications and variations as would be obvious to one of skill in the art are within the scope and spirit of the invention.