Residence Time - Incidents 1

There have been incidents where excess residence time, and thus inventory, was claimed as a contributing cause to an accident. <br><br>In my experience an accident or incident is the culmination of a chain of events and circumstances. Residence time can be a link in this chain of events and it may even be the root cause in some cases. <br><br>You should consider the ramifications of residence time in any hazard and operability study.

Lack of adequate residence time may be a potential cause for accidents in many cases. Three cases come to my mind immediately; these are:
a. Inadequate residence time in flare knock-out drums, which will lead to carry-over of liquid droplets to the flare tip and may result in liquid fire spray from the flare tip (unburnt /semi-burnt liquid drops).
b. Inadequate residence time in 3-pahase/2-phase separators, where gas stream is separated from liquid stream and sent for compression. Inadequate residence time may lead to carry-over of liquid droplets to compressors which may damage compressor internals badly.
c. Inadequate residence time in vessels like slug-catchers may lead to carry-over of liquids to downstream gas processing units (e.g. gas sweetening processes). Presence of hydrocarbon liquids in such processes may lead to operational problems like foaming which may result in major process upsets.