The standard bottom pack - off is type 'PBP-1'.

The bottom pack-off is installed in the lower flange of the casing head spool and tubing head spool to prevent the lower flange from being exposed to high pressure.

The bottom pack -off type 'PBP-1' seals the annulus pressure by injecting packing. The bottom pack - off PBP -2 is designed to give a positive annular seal with pressure energized oversize O-Rings.

For services at working pressures above 5,000 psi, the 'PP' seal is used.

When the bottom pack - off is used, the casing should be cut 90mm from the top flange surface of the connecting spool.