1,Application:
Used in conjunction with hydraulic control system, the annual BOP seals off the annulus of different sizes when pipes are in use in the hole. An annular BOP can also seal off the hole when no pipe is in it. When used in conjunction with the pressure-regulating valve and accumulator, the annular BOP allows snubbing service.
2,Working Principles:
A hydraulic control system is used to close or open the annular preventer. When it is closed, high pressure oil is directed to the closing chamber positioned in the lower side of the piston, causing the piston to move upward. The packing unit is compressed by the moving piston. Because the annular BOP has a cap, the packing unit can not move upward an only can move toward the center of the well to pack off a string or seal off the well.

3, Operating Requirements:
A, The annular BOP can be used to seal off a well where the drill pipe is in use if the well blows out. However, the annular BOP cannot be closed for a long time, because the packing unit is easy to be damaged and the BOP itself has no lacking mechanism. 
B,It is necessary to use a drilling tool with 18°bevel when running/retrieving drill of operation with BOP, running/retrieving drill should be slow pass through the nipple and all the rubber protecting collar on the drilling tool should be discharged off.
C,With the annular BOP in the closed position and shut-in pressure kept below 5MPa,the string can be moved either up or down, but mustn't be rotated.
D, It is forbidden to open the annular BOP to relieve the pressure out of the well to avoid rubber core damage.
E, Be sure to check whether the annular BOP is in the full open position or not every time after opened in order to prevent damage to the packing unit.
F, Clean the inside of the BOP after well cementing operation is completed in order to keep its closings and openings flexible.
G, More attention shall be paid to ring gaskets and gasket grooves during installation of the BOP or its removal from the service.
H, After entering the destination layer, running/retrieving drill once should be accompanied with test of well enclosed with drilling tool once, and inspect the effect of well enclosed with rubber core, if beyond the requirement, it should be replaced.
I, Periodically perform pressure test on the annular BOP in accordance with applicable standards.

1. Cap   2.Packing Unit
3.Support Ring  4.Piston   5.Body

4. Tapered Rubber Annular BOP

1,Upper housing and the body have two connection forms as connection by bolts and connection by claw chuck.
2,Annular BOP with tapered rubber is composed of seven parts as upper housing, wear plate, body, piston, tapered rubber, anti-dust ring supporting cylinder.
3,The dynamic seal of annular BOP adopts the sealing ring of lip structure, which reduces the wearing of sealing ring to maximum, and the sealing is reliable; the rubber is not easy to fold back, and there is the effect of funnel; and the well pressure has the function of assisting sealing, etc.

5. Spherical Rubber Annular BOP
1,Upper housing and the body have two connection forms as connection by bolts and connection by claw chuck.
2,Annular BOP with tapered rubber is composed of five parts as upper housing, body, piston, spherical rubber and anti-dust ring.
3,The dynamic seal of annular BOP adopts the sealing ring of lip structure, which reduces the wearing of sealing ring to the maximum, and the sealing is reliable; the rubber is not easy to fold back, and there is the effect of funnel; and the well pressure has the function of assisting sealing , etc.

6. Specifications And Technical Parameters Of Model A Annular BOP