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Secondary Seals


Secondary seals are used to seal around the production casing stub in the bottom of the bowl of the tubing head. The various types are described below:









Double FS-Seals
This design consists of two elastomer-shaped seals located in grooves in the bottom of the tubing head. A seal is achieved by interference of the seal with the outside diameter of the casing and the bottom or OD of its retaining groove. A spring molded in each inside corner of the seal provides an anti-extrusion mechanism when sealing against pressure by bridging the gap between the tubing outside diameter and casing head seal bore. The shape of the seal allows it flexibility to maintain sealing interference with the large variations in tubing outside diameter. 

These seals consist of a T-cap seal element, nonextrusion rings and a receiver ring. These components will fit the HPE bottom prep configuration. The PI seal is designed for use up to 15,000 psi working pressure and temperatures up to 75°F or as low as -50°F, depending on the elastomer selected. It provides the proper compression and squeeze even with the larger API casing tolerances. The design effectively intensifies the annulus pressure and thus the internal stress in the elastomer to minimize the effects of explosive decompression.

  SBMS-II Seals
This metal-to-metal seal consists of a "U"-shaped ring with a "bump" sealing surface at the outside and inside legs of the "U." When installed, the entry ramp compresses the legs of the "U" inward and creates contact stress in each "bump" that provides the seal. This seal requires the casing stub OD to be field machined after the casing is hung to provide the proper sealing tolerances and surface finish. This is accomplished with a portable pneumatic-driven tool. It is good for temperatures ranging from -75°F to 1200°F.

  RCMS Seals
The Rough Casing Metal Seal (RCMS) is designed to use up to 20,000 psi. This seal does not require special machining of the casing stub; is compatible with temperatures from -20°F to 350°F in corrosive environments; does not require special installation tools and is simple to install; is NACE compatible; is compatible with casing spool and tubing spool strength; is compatible with casing string strength properties.