Shaffer spherical annular Blowout Preventer is an important part of the well control devices. It is mainly used to control the wellhead pressure in the drilling, well work over and oil testing effectively preventing from the blowout accidents and working in safety. Shaffer spherical annular BOP can only be used when equipped with BOP hydraulic control device it is usually used with ram blowout preventer or separately. Shaffer spherical annular BOP sealing element has spherical and conical type.

The Shaffer spherical annular BOP is a relatively new entry into the annular preventer market. It utilizes a spherical head cover ing the top of the packing unit to translate axial loading on the packing unit into radial movement. The overall height of the preventer is somewhat shorter than either the Hydril or Regan but is higher than the Type “A”. Shaffer achieved this reduction in height through the use of a short piston and the spherical geometry of the head.