The design and manufacture of Annular BOP is according to API Spec 16A standard.Technical Specification
Packing element is spherical or tapered type with massive storage volume, low operation pressure and excellent sealing function
Bonnet is hemispherical-shaped, so there is no stress concentration on bonnet whenever bearing the pressure. so the pressure is evenly distributed; convenient for disassembly and assembly (except tapered packing element)
Piston is set in low position to have a shorter moving distance. Use wear ring on piston.
Lip type seal rings are used to realize long service life.