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186 Well Control for Completions and Interventions

Figure 4.33 Type “RX” ring gasket.

4.13.2.3 “BX” pressure energized ring gasket
The “BX” ring gasket is used with 6BX flanges where flange face-to-face
contact is allowed. Contact between the flange faces enables gasket com-
pression and plastic deformation to be controlled. As both the ID and
OD of the gasket may contact the grooves, holes are normally drilled
through the gasket to ensure pressure either side of the joint is balanced.
Sealing takes place along small bands of contact between the groove in
the flange and the OD of the gasket. The gasket is slightly larger in diam-
eter than the grooves, and so is compressed slightly to obtain the initial
seal as the joint is tightened. Variances in groove and ring gasket tolerance
mean that face-to-face contact is not always achieved. When this occurs,
vibration and external loads can cause deformation of the ring, leading to
a leak.

REFERENCES
1. Recommended practices for blowout prevention equipment systems for drilling wells. API
Recommended Practice 53. 3rd ed.; 1997.
2. NORSOK standard D001. Drilling facilities. 3rd ed.; 2012.
3. Recommended practice for well control operations. API RP 59. 2nd ed.; 2006.
4. API specification 6A. Specification for Wellhead and Christmas Tree Equipment. 20th
ed.; 2010.
5. Information from Cameron Schlumberger web page: ,https://cameron.slb.com/pro-
ducts-and-services/drilling/pressure-control-equipment/annular-bops/dl-annular-bop..
6. Information from GE/Hydrill web page: ,https://www.geoilandgas.com/sites/geog/
files/gea31279_gx_annular_blowout_r2.pdf..