Changes to Processes and Plants

This chapter elucidates the processes industries need to look at systematically for possible consequences before making any change to plants or processes. Many publications describe accidents that occur because no one foresees the results of such changes and suggests procedures for preventing such accidents in the future. Nevertheless, as the illustrated examples in this chapter show, unforeseen consequences still occur. Sometimes there is no systematic procedure, sometimes the procedure is not thorough or is not followed, and sometimes the change is so simple that a formal review seems unnecessary. There is also reluctance in many companies to look in the literature for reports of similar situations. Certain changes like scale-up or unrecognized scale-up ignorance of a reaction are listed as causes of process failures. Changes to plant equipment have also been known as a cause for failures like in change of direction flow, adding insulation, or some unauthorized changes. Various other examples are also discussed in this chapter. Another mode of failure is associated with gradual changes such as in concentration and maintenance, procedures that span over a period of time. A most common cause of error is when changes are made because the reasons for equipment or procedures have been forgotten. As in medieval England where there were officials called Remembrancers whose job was to remind the king's courts of matters that they might otherwise forget, every process plant needs such persons.