annular BOP features compact structure. It can seal square drill rods, drill rod subs, drill collar, casing strings and cables in various shapes. It keeps constant pressure down hole while the drill is driven into or out of the well. Annular BOP takes on two shapes, ball-shaped and cone-shaped. And Ball-shaped BOP falls into bolted cover type (B type) and wedge cover type (W type), both of which are small and light, suitable for air shipping. And they can work in low temperature circumstance.
How an Annulus BOP Works
How an Annulus BOP Works
A hydraulic control system is used to close or open the annular preventer. When it is to close the BOP, high pressure oil is directed to the closing chamber positioned at the lower side of the Piston, causing the piston to move upward. The packing unit is compressed by the moving piston. Limited by the BOP top cover, the packing unit can not move upward is forced to the center of the well this to pack off a string or seal off the well.
When it is to open the BOP, shift the reverse valve and direct high pressure oil into the opening chamber at the upper side of the piston to drive the piston downward. The closing chamber will then recede, and the pressure on the packing unit is removed, and the well is opened.