Image Number 5 for United States Patent #7252153.
A fluid loss device including a flapper and seat assembly that provide a seal on a lower flapper surface when the flapper is closed and resists pressure in either direction. The flapper and seat assembly is spring biased to contact a flapper support above the flapper to resist deformation of the flapper due to a pressure differential from below the flapper. The flapper and seat assembly may be moved by tubing pressure to release an opening prop that opens the flapper. The valve seat may include an elastomeric seal element to improve the fluid flow restriction. The flapper and seat assembly is also biased upward by a pressure differential from below to above the flapper, to thereby increase the flapper to valve seat pressure as the fluid pressure differential increases.