Rethinking Bhopal- A Process Safety Perspective

Author of ‘Rethinking Bhopal’, Kenneth Bloch, is a process safety professional who has taken a very deep interest in the Bhopal Disaster story. Rethinking Bhopal is a meticulously researched account of history’s worst single-incident industrial disaster. It contextualises the process facts of the Bhopal plant, comparing them to accepted norms, and presents them in a relatively easily-digestible format. A major aim of Rethinking Bhopal is not just to produce a historical account of one terrible disaster but to engender better thinking and practice within industry professionals operating today.

Kenneth Bloch has now put together, for our benefit, a four-part series that explains the important technical elements of the Bhopal Gas Tragedy:

“The Bhopal Gas Tragedy drove improvements that made industry safer. By protecting the lives of others, industry now honors those whose lives were suddenly changed on December 3, 1984 – some of whom may read this blog regularly. Among these are survivors who lost their health, family, or friends. Also included are workers and others who designed, operated, and maintained the equipment that became hostile. Like parents of a rebellious child that was raised and nurtured with love, care, and affection to be a productive member of society, their unjust sense of hindsight must be unbearable. My heart goes out to all of you.

“It is with deep respect for personal sacrifices involuntarily made to benefit industry that I offered my friends at the Bhopal Medical Appeal a 4-part “Technical Series” on the Bhopal Gas Tragedy. The topics speak to those with positions in industry today who might incorrectly think that the Bhopal Gas Tragedy does not apply to them. They introduce fundamental process control and safety concepts to those entering the industrial workforce today – many of whom amazingly have not heard about the incident previously! The series also explains to the curious how good things we control can become hostile under our watchful care.
“In many ways, the Bhopal Gas Tragedy affects us all even if we never see the inside of a factory. The series will help anyone determined to make a difference “rethink” their actions before going too far. I thank the Bhopal Medical Appeal for accepting my offer and I hope that readers will learn something valuable from each installment of the series.”

 

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Series 1 of 4: Methyl Isocyanate (MIC) Rundown & Storage System

The series begins with a Process Flow Diagram (PFD) of the MIC Storage System that was involved in the Bhopal Gas Tragedy. The drawing is “As-Built,” which means that it shows the system as it appeared upon placing it in service. The PFD reveals how the process was both remarkably efficient and vulnerable.
When reviewing the PFD, pay close attention to (1) using carbon carbon steel for all equipment in MIC vapor service, (2) the need for a clear, open, unobstructed path between the E-210 MRS and the E-408 VGS atmospheric vent, and (3) nitrogen injection into the E-610, E-611, and E-619 tank head manifolds. An unbreakable dependency was formed between these three items, which made it impossible to change one without impacting the others. The dependency was rooted in deviating from a design standard that prohibited the use of carbon steel for equipment in MIC service.
Adherence to the design standard would have resulted in the use of stainless steel in MIC vapor service, where carbon steel was used. MIC polymerizes upon contacting rust; thus, a rust-resistant material such as stainless steel was needed to avoid incompatibility complications. Why was carbon steel, which would rust upon contact with air, used instead? To save money by reducing construction costs.
Saving money is something that most people can relate to. Most people must learn to survive on limited resources that prevent us from spending more money than we make. The same is true for any company that expects to stay in business. Companies that spend more money than they generate will eventually go out of business. Looking at the PFD, it becomes clear that the system was designed to operate under a continuous nitrogen purge starting at the storage tank heads and terminating upon its discharge through the VGS atmospheric vent. Stainless steel resists rust, but nitrogen in this case does the same thing by eliminating oxygen (air) that carbon steel needs to rust. The purpose for nitrogen was to eliminate air that could allow MIC in the storage tanks to ignite. It also served as a corrosion inhibitor for carbon steel equipment found in MIC vapor service by preventing air from migrating into the system through the atmospheric vent.
When I look at the drawing I see an efficient, compact, and reliable process design. On paper, everything works perfectly. But although perfection is the goal we all work toward, nothing could be further from our reach when operating a typical industrial process.
Part 2 HERE
Girl with candle Bhopal

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