What Went Wrong?

Chapter 18. Reverse Flow, Other Unforeseen Deviations, and Hazop

[To] divide each of the difficulties under examination into as many parts as possible, as might be necessary for its adequate solution.—René Descartes (1596-1650), Discourse on Method

This chapter describes some incidents that occurred because of deviations from the design intention, as expressed in the process flow diagrams (also known as line diagrams or process and instrumentation diagrams). The fact that these deviations could occur was not spotted during the design stage, and they had unfortunate unforeseen results. Ways of spotting these deviations by conducting hazard and operability studies are discussed in Section 18.7.

Errors introduced during modifications are discussed ...