The secondary seals are assemblies used for sealing the annular space between the production casing and located into the bottom flange of the casing head spool.
The secondary seals are utilized with the casing head spools, tubing heads of the Christmas trees, circulating heads, pumping heads and packoffs.
The secondary seal also permits the determination of the pressure in the space between the primary and secondary seals outside the spool by means of the ball valve.
There are several design types of secondary seal:
- BREDA – type secondary seals, and
- PP – type secondary seals.
The BREDA – type secondary seals are the most utilized seals while the PP – type ones require the use of a cone valve through which soft packing is put into for sealing the casing.
The secondary seal sizes are in accordance with those of the spool and casing to be sealed.
For more information, please consult the wellhead equipment brochure here