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the stack prior to running.
The pipe rams are operated hydraulically, when necessary,
to close and seal around the drill pipe. Their normal operating
pressure is 1,500 psi. Cameron pipe rams are equipped with
hydraulic wedge locks to hold the rams in closed position. The
wedge locks must be hydraulically retracted to open the pipe rams
again. Shaffer and Hydril rams have an automatic lock
incorporated in their operating mechanisms.
The hydraulically operated blind shear rams can cut
through the drill pipe to seal off the BOP stack bore in an
emergency. These rams also operate at 1,500 psi but usually have
larger operating mechanisms than the pipe rams. The blind shear
rams have a locking feature that must be released to open them
again.
The annular or bag-type preventer is basically a rubber
cylindrical element with bonded metal ribs. When hydraulically
actuated, a large piston compresses the rubber element, which then
closes on the drill pipe, casing, or itself. The metal ribs help it
return to the fully open position. Standard operating hydraulic line
pressure for annular preventers is 1,500 psi. Some types of annular
preventers must close against the hydrostatic pressure in the riser
column; therefore, a pressure-balance system is incorporated for
counteraction. Annular preventers used in offshore operations are
normally rated at 2,000, 5,000, or 10,000 psi working pressure.
The hydraulic connectors used between the wellhead and
the BOP and between the BOP and the riser are controlled from
the surface and are of two basic types: mandrel and collet.
Mandrel-type connectors utilize hydraulically actuated cams to
drive locking dogs into the grooves machined into the wellhead.
The collet connector uses a series of collet fingers to form a funnel
configuration to guide the connector over the well hub. Both types
of connectors use AX or VX rings for sealing.
Usually, two choke-and-kill lines are run down to the BOP
stack, either integrally with the riser or as independent lines.
Choke-and-kill valves provide subsea shutoff of the high-pressure
lines and are part of the stack, controlled by the BOP control
system. Most BOP stacks have connections below all rams to
allow different choke-and-kill hookups, as many operators have
specific requirements with regard to the placement of choke-and-
kill entry lines within the stack.
Each choke-and-kill line usually carries two fail-safe close

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