Recently there’s been some robust discussion over on the Safety Critical Mail List at York regarding the utility of safety cases and performance based safety standards (as exemplified by the UK safety case regime) versus more prescriptive design standards (as exemplified by the aerospace industry FAR regulations). To provide one UK regulator’s perspective here’s a presentation by Taf Powell, Director of the Offshore Division of Health and Safety Executive’s Hazardous Industries Directorate, UK, on the state of safety cases in the UK offshore industry circa 2005. Of course his talk was well before the 2010 Deepwater Horizon disaster.
The presentation provides a very interesting perspective on the challenges of the the industry and the sins of probabilistic thinking:
… Global companies set their own performance standards for their operations. Under pressure to lift production, the major companies are degrading their own standards, often using probabilistic and uncertainty calculations to try to justify this.
From his perspective while safety cases are very revealing for a new facility, the safety case over time has not prevented high rates of asset degradation, due to cost cutting measures. This degradation has in turn resulted in adverse effects upon overall asset integrity e.g. keeping the bad stuff contained and maintaing primary structure integrity.
What began as cutting corners in things perceived as non safety critical such as painting, rapidly became a culture of shortcomings, maintenance backlogs, seized plant hindering maintenance shut-downs and escalating outages which reduced profits and led to further cost-cuttings, down-sizings etc. Particularly ahead of divesting assets.
Interestingly when the HSE looked at the accident data (circa 2000 to 2005) in more detail they found that the ratio of fatal to less severe accidents was increasing over time. The HSE also found that the mobile drilling fleet was comparatively worse that other parts of the industry. There is an interesting parallel here to changes in the decadal distributions of accident severity in the aviation industry.