Page 572 - Marine Structural Design

548 Part V Risk Assessment

The consequences of failure may depend on the type of risks considered, e.g. personnel risks,
economical risks and environmental risks. An example category of failure consequences is
given below,
. Catastrophic - fatality or disability injury; major loss of the FPSO or long-term loss of its
production; serious oil and gas release resulting in long-term damage to the environment.
Critical - severe injury; major damage to the FPSO or its production; significant oil and
gas release.
Significant - non-severe injury; some damage to the equipment and systems and minor
loss of production; oil/gas release requiring regulatory notification.
Minor - no injury; minimum component failure and no loss of production; record-able
event but no regulatory involvement.
The physical phenomena to be considered in consequence modeling include:
Release modeling, multi-phase, near field flow regime and internal-pressure time history
Thermal radiation effects to humans and equipment from jet fires and pool fires.
Explosion over-pressure that impacts human and equipment
Evacuation of personnel on board
30.6.4 Risk Estimation and Reducing Measures
If risks are unacceptably high, measures are to be taken to eliminatdreduce the risks.
Examples of the approaches to reduce risks are,
modify the design to eliminate the hazard,
reduce the frequency of occurrence of an initiating event,
reduce the fi-equency of the events that may cause an initiating event to become an
accidental event of unacceptable consequences,
reduce the exposure of personnel and equipment to the hazard,
implement strict operational procedures, safety procedures and emergency response
program.
More specifically major risk estimation and reducing measures include the following,
Process Leakage
Process systems are often the main contributor to personnel risk. The gas compression has the
highest leakage frequency followed by the fuel gas system and the gas dehydration system.
Most of leakage is small, e.g. less than 10 mm equivalent hole size. The process leaks may
lead to explosions and fires. Pollution from process leaks is limited by the process shutdown
and isolation system, unless an explosion with subsequent fire escalates to the cargo tanks and
threatens the overall integrity of the vessel. The process leak may be reduced by: relocating
process control center to within the accommodation, installing a protected escape route from
bow to stern, installing additional gas detectors in the process area.
Offloading and Shuttle Tanker Risk
There are two types of oil offloading systems, namely tandem assisted offloading and single
point mooring. The former is used with turret moored FPSO and the later is applied with