FPJ inside BOPValve is a kind of check valve with large pressure drop Valve seal is arrow type  valve  seal  the  arrow  type  check  valve  will  shut  down  rapidly  under  the  action  of reverse  circulation  pressure  insidedrill  tools  and  spring  force,cut  off  the   inner  channel of drilling  tools,to  prevent  blowout  purpose  in  the  drilling  tools.It  can  be  placed  on  the platform for standby,or it can be installed between the drill pipe and drill bit after removing the  jacking   device  to  prevent  high-pressure  oil  and  gas  eject  from  the  drilling  tool.A dedicated  release  tool  keeps  the  valve  normally  open  and  allows  reverse  flow  topass.This dedicated  release  tool  pre-installed  in  the  valve  and  the  assembly  prepared  on  the  drilling platform,for quick installed on the drill string when the first signal appears when drill pipe lifts out from the well