Positive lockdown for metal seal

In a well assembly having a wellhead housing having an axial bore, a hanger secured to a string of conduit and supported in the bore, a metal seal located between the hanger and the bore, the seal having radially spaced apart inner and outer walls, and an energizing ring which is moved from an upper position to a lower position forcing the inner and outer walls further radially apart to set the seal, an improved means for locking the seal to the wellhead housing, comprising in combination:

• an annular recess formed in the bore of the wellhead housing;
• a split lock ring carried by the energizing ring above the inner and outer walls of the seal and being movable between a contracted position to an expanded position located in the recess, the lock ring having an upward and inward facing tapered surface;
• and
• a wedge ring carried above the lock ring by the energizing ring for movement therewith, the wedge ring having a lower portion which has a downward and outward facing tapered surface that engages the tapered surface of the lock ring to push it to the expanded position when the energizing ring moves to the lower position, the lower portion having an inward facing wall that is spaced radially outward from the energizing ring, defining a cavity so as to allow the lower portion to deflect once the lock ring is in the expanded position, to allow the energizing ring to continue downward movement if necessary to fully set the seal.