Page 132 - test2

The Deepwater Horizon had multiple inspections and surveys that should
have included the inspection of the engine overspeed shutdown devices. The
panel has been unable to ascertain exactly when each overspeed device was
tested. Accordingly, ABS indicated that it inspects 20% each year; however,
neither ABS nor Transocean document which devices are tested to ensure that
the same device is not tested each year and that all devices get tested within the
rotation frequency. The failure of ABS and Transocean to document which
devices are tested to ensure all devices are tested is a possible contributing
cause of the DWH explosion.

The emergency shut‐down response on a DP MODU utilizes a different
operating philosophy than employed on moored MODUs. Instead of the single
top level shutdown of all engines, the DP MODU rig is designed with an
emergency disconnect capability from the wellhead in order to escape the
hazardous area in the event of an uncontrolled blowout. Based on this mindset,
the engines should not be shutdown because of the need for DP power. Even if
the process of manual activation is fully understood by those responsible for it
on a DP MODU, it adds additional complexity to response of the well control
event. Further, the philosophy creates a conflict since the rig needs to maintain
power to get off location while maintaining that power creates a possible ignition
source during the presence of free gas on the rig. The DP MODU operating
philosophy when considering the performance of an Emergency Shutdown
(ESD) is a possible contributing cause in the Deepwater Horizon explosion.

D. Other Possible Ignition Sources

1. Electrical Equipment in Hazardous Areas

The most likely location for the ignition of flammable gas by unguarded
electrical equipment would be in the area on or near the drill floor. The
Deepwater Horizon drill floor required the use of properly maintained and
certified explosion‐proof, intrinsically‐safe, or purged and pressurized
equipment, which should have prevented the ignition of flammable gases by any
electrical equipment installed in this area. The Panel found no evidence that the
electrical equipment located on or near the drill floor’s hazardous area was a
cause of the ignition.

127