h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

In my days as a chemical engineer, I was involved in a project to build a new plant using nitromethane (NM) as a feedstock, available from a supplier in an adjacent state. This is a highly flammable substance that contains its own oxygen AND fuel, somewhat like rocket fuel, and is the liquid used in some high powered drag race machines.

On two occasions decades ago, very large craters were left by exploding tank cars of NM. The U. S. Dept. of Transportation (DOT)ran many test such as firing shells into drums of NM, but could never generate an explosion - fire, yes, but nothing to explain the craters. The DOT eventually required that NM be shipped in drums only - a major headache for my proposed project, especially the empty drums.

So what caused the explosions? It was finally concluded that an accident nearby caused another tank car to fly up and land on the NM tank car, causing a rapid adiabatic (no loss of heat) compression inside the heavy walled tank car. This led to the massive explosion. A thin walled drum is not strong enough to generate that kind of pressure buildup, the wall will fail quickly.

I suspect if anyone had brought this up during early talk on NM tank car design (not very likely), someone would have said "What are the odds?"

(Another cynical quotation regarding DOT regulations - "If propane were discovered today, they would not let us ship it.")

Ah, chemical engineering - that's my BS degree (Bachelor's of Science for non-USA readers). Nice story about the NM tanker, thanks for sharing it! There seem to be some cases wherein making a container of some sort a bit TOO strong for its own good introduces another failure mechanism (or maybe just making an existing one more likely). Complex stuff.


- JD

Yup, my response was to your fine entry.

But on the other hand we should all be thankful for the American Society of Mechanical Engineers (ASME) and their extensive standards for pressure vessel design. After a series of boiler explosions a century or so back - some in schools - the ASME standards virtually eliminated pressure vessel failures in new equipment. The ME's (who all agree that Chem. E. and BS go well together ) did a great job on this issue.

The last time I was involved, the issue had become vessels and piping that were 50 years old or more. A huge problem is determining the acceptable pressure rating of such equipment - which is in many, many Gulf Coast (USA) refineries and chemical plants.

"The ME's (who all agree that Chem. E. and BS go well together ..."
Ahhhh, the good ol' MechE/ChemE rivalry! We used to play pickup games of football against each other on the half-size field out in the horseshoe park on my old campus - we had great fun, us ChemEs! Due to some freak of statistics (or possibly freak of nature!), us ChemE's back in those days were of the large, ex-football playing, athletic type. (I myself have always wanted to play rugby very badly, and after years of practice I can finally say that I do indeed play rugby very badly ). When I left school, I believe we were still unbeaten by the MechEs!

I nearly worked for the petroleum industry in your part of the country - for Chevron, in fact. But, one thing led to another, and I visited Beaumont and Longview and other areas, and decided I was more of a dry-weather kinda guy - so I stayed in New Mexico and eventually got into the risk assessment biz from here.

FWIW, the nuclear laboratory industry is also wrestling with aging facilities and equipment. Tough problems to solve.


- JD