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Well Control Surface Equipment 161

Figure 4.15 Shaffer (NOV) spherical annular preventer.

elements spherical shape causes it to close as it moves upwards. The
Shaffer BOP can close on open hole (Fig. 4.15).

4.7.5 Care and use of annular preventers

Although the drilling contractor is normally responsible for the installa-
tion, use, maintenance, and testing of the annular preventer, supervisors
should have a good understanding of the basic principles of operation.
This will enable them to ensure that the system is being properly main-
tained and operated. The following guidance is relevant to most
operations:
• The lifting eyes on the annular body are for lifting the annular only,
and not the entire BOP stack.
• If visible, check the color code on the annular element. It should cor-
respond to the elastomeric compound that is compatible with the
completion or workover fluid being used. For a description of the var-
ious packer compounds and color code (see Table 4.3).
• Shut-off valves are often placed in the open and close lines (for line
testing and isolation purposes). Make sure these valves are fully open
whenever the annular is in use, so it can be closed if necessary.
• H 2 S exposure causes a slow hardening of materials and loss of elasticity
in most annular elements.
• Ensure that opening hydraulic pressure is applied to the annular when
tripping pipe. This pressure keeps the element packing fully retracted
and avoids mechanical damage.
• Keep the manufacturer’s operating manual on location. It contains
valuable information about preventer weight and dimensions, closing