Could this hazard have been discovered if a computer assisted HAZOP was performed?

posted Jan 28, 2017, 12:00 PM by Niels Jensen   [ updated Mar 22, 2017, 3:32 AM ]

Blocked In - Williams Olefins Plant

Safepark certainly believe the answer to this quesiton is YES. The reason is that MFM models of the unit can easily be developed, and that such models allow the reasoning about causes and consequences of deviations, the results of which would assist HAZOP teams during either a MoC or HAZOP study. A simple model could be developed with less than a days work by an expert in MFM model development.

The video to the left was recently released by the #CSB. A small design change that was performed at the Willams Olefins Plant many years ago to allow a distillation tower to run with just one reboiler instead of two in parallel resulted in 2013 in an #overpressurization and rupture of one of the reboilers. The resulting explosion killed two workers and injure many more. A copy of the CSB Case Study can be downloaded from this page. The above pictures are curtesy of CSB.

The design change resulted in it being possible to isolated the reboiler from its protective safety valve. This hazards was not discovered during a MoC or 3 later PHAs. That different teams of experts did not identify the hazard which caused the explosion in 2013.

I would be relatively easy to construct a functional model using multilevel flow modelling (MFM) to investigate possible overpressure scenarios, and hence identify the hazard, which humans overlooked. Safepark is involved with a Danish research group at DTU, which is working to make computer assisted HAZOP a reality for situations, such as this one. 
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Niels Jensen,
Jan 28, 2017, 12:05 PM