| 摘要 |
An apparatus for rapid venting of the compressed air and deballasting of a buoyant air tank in a positively buoyant riser system in the event of a premature drive off or a riser section parting is shown. The rapid venting of the compressed air ensures that the riser section cannot rapidly ascend to the surface and damage the drilling rig positioned above. In a first embodiment, the buoyancy tank or housing includes a vertical channel positioned on its exterior. A cover plate is placed over the vertical channel and sealed in place by a frangible weld. A tether line attaches to the cover plate and extends to an anchor point on the BOP stack below. In the event of a catastrophic parting of the riser, as the riser sections and attached buoyancy tank or housings begin ascending, the tether line is drawn tight. Further ascension of the buoyancy tank or housings, causes the frangible weld joints to break and peel back the cover plate, exposing the vertical channels. This causes an immediate and complete venting of the buoyancy tank or housings, rendering them negatively buoyant. Alternate embodiments are also shown.
|
