One, the annular BOP function

1, when there is no drill hole, annular preventer can fully closed wellhead (referred to as a zero).

2, in the drilling, coring, well logging, casing, completion operation from overflow and blowout, can annular space is effectively closed the Kelly, drill pipe, drill pipe, drill collar, the formation of coring tools, pipe, cable, tubing and other tools and wellbore (referred to as the seal ring air).

Butt welded drill pipe 3, the annular BOP is 18 º slope joint in the closed time (control pressure regulating valve in the decompression under), forcibly tripping (also known as non snubbing operation).

[SY/T6426-2005]: in a pressure less than 7MPa case, were not snubbing operation with the annular BOP, should use the 18 º ramp joint drill, drill speed shall not be more than 0.2m/s

Namely: to close the various drill, empty well, when necessary, tripping.