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The microprocessor‐based control system on the Deepwater Horizon BOP
stack received AC power from an uninterruptable power supply unit, which was
designed to keep surface and subsea equipment operational under all conditions.
All primary functions of the BOP stack were controlled through the multiplex
cables, which connected the rig to the BOP stack. As a result, the loss of the
multiplex cables would result in loss of power and loss of control of these
functions. To ensure operational redundancy and AC power supply, the
uninterruptable power supply unit included a battery system able to provide
power to the panels, diverter controls, event logger and pods for at least two
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hours of normal operation.

Cameron offers an option for a rig to have the ability to monitor each
pod’s battery voltages from any control panel. The Deepwater Horizon did not
have this additional Cameron technology, which would have enabled the rig
crew to monitor battery voltages.

C. Emergency Disconnect System

The emergency disconnect system is a system that can allow the rig to
separate from the BOP. This system can be activated from three different
locations: (1) the drillerʹs control panel; (2) the bridge; or (3) the subsea engineer
control room. The BOP had two emergency disconnect systems sequencing
options, referred to as “EDS 1” and “EDS 2.” Both emergency disconnect system
options were designed to close the BSRs, close the choke and kill valves, and
unlatch the LMRP Connector, along with choke and kill connectors. EDS 2,
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however, would also activate the casing shear ram. The step‐by‐step
sequences for the Deepwater Horizon’s emergency disconnect system are in
Appendix H.

The hydraulic power to perform the emergency disconnect system
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sequence came primarily from the conduit. Upon activation, however, two
functions – the high pressure closing of the BSR and of the casing shear ram –
would receive their hydraulic power from the BOP stack mounted accumulators.

330 Id.
331 BP‐HZN‐MBI00010443.
332 Id. The conduit in turn received its supply from the hydraulic power unit from the surface.
This unit had at least two triplex pumps to supply the pressure to the accumulator bank through
the conduit.

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