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What small hole on BX ring gasket use for


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ring_gasket_bx_axial_hole

Ring gasket is a device use for sealing connection points in piping or valve system and BOP stacks. This sealing device plays an important role in wellhead pressure integrity since most failure occurred due to fail sealing performance which may lead to cut out connections.

API 6A dictated BX ring gasket as a type of ring gasket to be used with type 6BX flanges and type 6BX hubs. BX pressure energized ring gasket was designed for face to face contact of the hubs or flanges. Sealing takes place along small bands of contact between the grooves and gasket OD. Gasket is made slightly larger in diameter than the ring grooves. It is compressed slightly to achieve initial sealing as the joint is tightened. As the design intent of BX design was face to face contact between the hub or flanges, Proper way of installation need to be done in order to prevent vibration and external loads which can cause plastic deformation of the ring and may eventually result in leaks. Both flange and clamp hub BX joints are equally prone to this difficulty.

BX gasket is manufactured with small axial holes on it for equalizing pressure purpose. The tension in flange bolts (or clamp hubs) forces the ring to fit creating stresses that ensures rings elasticity creates a seal even when everything is relaxed. The hole is required to equalize pressure in the pockets that are formed between the groove and the ring. If a pressure differential existed across the ring, the stresses that are generated within the ring will be distorted.

Those axial holes also prevent pressure from being trapped under the ring, and harming someone during disassembly process. The term pressure energized deals with the fact that internal pressure against ring gasket ID forces ring gasket OD to seat with greater loads against the outer side of ring groove.

 Reference:

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