Page 168 - Well Control for Completions and Interventions

160 Well Control for Completions and Interventions

The manufacturers list the following features:
• Packing unit specially molded with two different styles of inserts to
reduce closing volume and increase closing cycles.
• Replaceable wear plate that eliminates metal-to-metal contact between
the packing unit inserts and the BOP head.
• Piston design that provides complete balance, reliable operation, and
ease of assembly.
• Latched head for fast, easy access to the packing unit and wear seals.
• Opening chamber head that prevents debris from falling into the
chambers when replacing the packing unit.

4.7.4 Hydril GX annular preventer
The GX annular preventer can be used for surface and subsea operations.
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It is available with 11, 13/8 and 18/4 in. through bore, and 5000 or
10,000 psi working pressure. The manufacturers state that the “GX annu-
lar BOP can hold full-rated working pressure after more closing cycles and strip-
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ping than any other unit available.” They also list the following features:
• Single packing unit that closes on any size pipe or an open hole—and
handles stripping.
• Only two moving parts, the piston and packing unit, for less wear.
• Latched head for fast, easy access to the packing unit and wear seals.
• Replaceable wear plate that eliminates metal-to-metal contact between
the packing unit inserts and BOP head.
• Pressure balanced piston design that allows use in ultra-deep water.
• Opening chamber head that prevents debris from falling into the
chambers when replacing the packing unit.

4.7.4.1 The Shaffer’s (NOV) spherical annular preventer
The Shaffer’s spherical BOP is so-called because of the shape of the seal
element and the internal chamfer on the top cover (either wedge or
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bolted). It is available in a range of sizes from 4(1/6) in. to 21/4 in.; NOV
also makes a 30 in. version of the spherical BOP, but it is not API
classified.
Working pressure ranges from 1000 psi for the 30 in. preventer,
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through to 5000 psi for the 7(1/16), 9, 11, and 13/8 in. models, and
10,000 psi for 4(1/6) in. and 7(1/16) in. models.
The Shaffer BOP is relatively simple to operate compared with other
annular BOPs. Maximum closure pressure is 1500 psi. When hydraulic
pressure is applied, the piton pushes up against the seal element. The seal