Page 274 - Drilling Technology in Nontechnical Language

Chapter 11 – WELL CONTROL 265

8. A pressure regulator that feeds fluid from the low-pressure

manifold to the bag preventer control valve. Bag preventers
operate at a lower pressure than ram preventers (normally about
800 psi), but as the seal element gets worn, higher pressure is
required to make the bag seal around pipe. This regulator is
also used to lower the closing pressure to the bag preventer if
it is desired to strip pipe in through the preventer, as described
previously in this chapter.
9. Two sets of pumps to maintain system pressure. One set is driven
by compressed air from the rig air system, the other is powered
by electricity. This provides some backup in the event of either
the rig air or electric system failing. The air-driven pumps give a

higher flow rate and generally pressure up the system to around
2,800 psi. The electric pump tops up the system to the full

pressure of 3,000 psi at a lower flow rate.

Fig. 11–7. BOP control system, land rig

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