During the past decades, the equipment, system and interface complexity have rapidly increased. Conventional quantitative risk management methods may not be sufficient for identifying interlinked and/or human-caused failure sources in complex subsea systems.
Most accidents, such as Deepwater Horizon, occur due to a series of complex and interlinked failures, often caused by human decision-making. Hence, supplementing the risk assessment toolbox with specialised methods may be effective in identifying and mitigating possible hazards.
A Hazard and Operability (HAZOP) study is a multidisciplinary risk assessment workshop where a system is examined using a systematic approach. The system is divided into subsystems, i.e. nodes. For each node, possible failure scenarios and corresponding consequences are identified by the use of guidewords. It is one of a few forums where experts from all disciplines are gathered. This expertise is tried utilised through creative discussion; operational and dynamic aspects are also highlighted and focused on during the reviews.
Globally, the HAZOP tends to be a strict workshop setting where documentation of all more or less serious failures is in focus. However, this approach is considered to restrain creative discussion. The “Norwegian Approach”, on the other hand, has been found efficient in identifying failures in complex systems. Participants are encouraged to have creative discussions and to think outside the box. The quality of the discussion is in focus. Hence, failures that can be classified as trivialities are not discussed, but rather time is spent on identifying those failures often caused by complexity, interface or operational failures. Due to the high maintenance costs of subsea systems, availability requirements and the need for profitability, the most efficient risk assessment tools must be used. The creative HAZOP approach utilising available expertise in an innovative way and focusing on operational aspects should be an obvious part of this toolbox.