Process safety assessment of new and existing plants

Companies of the Royal Dutch/Shell Group operate a very wide range of manufacturing installations which include oil refineries, gas processing and liquefaction plants and chemical plants.

The safety assessment of these installations is approached from a background of experience. The necessary experience to do this is continously brought to bear in design by involving appropriately selected staff and by applying established guidelines, standards and design/engineering procedures throughout the development of a project. In addition, structured safety reviews are carried out to check that all aspects have been properly dealt with.

The safety assessment of existing plants follows a pattern of enquiry which is similar to that for new plants.

Finally the question of residual risk is addressed: in general the assessment of the consequences of a failure scenario is more reliable than the judgement of its probability. Nevertheless there are instances where a closer look at probabilities can help in making design decisions. It is questionable whether risk analysis results can be used meaningfully in an absolute sense to judge the acceptability of an installation.