East Palestine, Ohio: An Abnormal Accident

 

When a wheel bearing overheated on a train carrying five tank cars of vinyl chloride through East Palestine, Ohio on Feb. 3, a sequence of events began that turned into a major accident with nationwide political implications. 

 

Overheated bearings (so-called "hot boxes") are not new to railroading.  With the thousands of wheel bearings in use every day, it's almost inevitable that some of them will fail by running hot and basically grinding themselves to pieces.  What is new in the last few decades are a number of safety devices that the railroads have installed to deal with overheated bearings. 

 

The Ohio train's bearing was sensed by three track-side hot-bearing detectors.  The National Transportation Safety Board (NTSB) has determined that one sensor noted the suspect bearing was warm (38 F above ambient, which was a cold 10 F) about twenty minutes before the derailing occurred.  Ten miles and 12 minutes or so later, it had heated up to 103 F above ambient.  The detector system's threshold was set so that these readings did not set off an audible alarm in the cab.  But the third sensor's reading of 253 F did.

 

By that time, it was too late.  Trains up to a mile or more long can't be stopped on a dime.  Three crew members were on the train, all in the lead engine.  By the time the engineer stopped the train, they could see fire and smoke behind them.  The train dispatcher authorized the crew to set hand brakes on the lead cars and move the front engines a mile or so down the track to safety. 

 

A total of 38 railcars had left the tracks, and the ensuing fire damaged 11 more.  Firefighters determined during the following two days that some intact tanks of vinyl chloride were heating up.  This chemical, which is used to make the ubiquitous plastic PVC (polyvinyl chloride), can undergo a spontaneous polymerization reaction that can cause an explosion.  To avoid that dire consequence, firefighters released the vinyl chloride into ditches they had dug nearby and burned it. 

 

Subsequent news coverage has dealt with the environmental consequences of the release of vinyl chloride and other toxic chemicals into the air, water, and soil around East Palestine.  One news report says monitors have estimated about 43,000 animals have perished, but 38,000 or so of that number were non-endangered minnows.  Residents have complained of odd tastes in the drinking water and air, and extreme measures have been and will be taken to clean up the extraordinary mess that several tank cars of toxic chemicals can make.

 

In an interview, NTSB chair Jennifer Homendy said that the accident was "100% preventable."  On the face of it, that makes railroad operator Norfolk Southern look pretty bad.  But exactly how could this accident have been prevented?

 

Certain safety requirements such as advanced braking systems for "high-hazard" trains that the Biden White House said the Trump administration removed would not have made a difference in this case, according to Homendy.  So attempts to turn the accident into a political football seem to amount to more smoke than fire, so to speak.

 

Norfolk Southern may rethink their thresholds for hot-box detectors.  This particular bearing seems to have gone from barely sensibly warm to disintegrated in less than 30 minutes.  The spacing and sensitivity of such detectors is a matter of engineering judgment, and accidents have a remarkable way of leading designers to reconsider safety precautions and adjust them so that the previous accident, at any rate, will not happen again. 

 

Too low a threshold on the detectors would mean that the trains are stopping needlessly, as a bearing may run warm for some unknown time before it fails.  Only the railroads have the statistics on these kinds of problems, but now that we know what can go wrong if the detection system doesn't stop the train in time, there may be a lot of readjusting going on in the future.

 

Some statistics from the Federal Railroad Administration cited by National Review say that train accidents caused by axle and bearing-related failures have fallen 59 percent from 1990 to 2019, largely due to the use of hotbox detectors.  So far from doing nothing about the problem, the railroads have been steadily improving their performance in this regard.

 

Sociologist Charles Perrow devised the term "normal accident" to express the type of mishap that very complex systems such as nuclear reactors can produce when multiple interacting parts do something that is very hard to predict, let alone forestall.  The East Palestine derailment was not that complicated.  But the system that should have prevented it failed in this case, and because of the particular cargo being carried, the consequences were awful. 

 

Despite an apocalyptic-looking crash scene, no one was killed or even injured in the derailment or fire.  This accident was far less consequential in that sense than the one, also involving derailed tank cars, that devastated the town of Lac-Mégantic, Quebec, on July 6, 2013 and killed 47 people.  So as bad as the East Palestine situation is, it could have been much worse.

 

Norfolk Southern is going to be paying for the consequences of this accident for a long time.  Already, millions of gallons of contaminated firefighting water have been shipped to Deer Park, Texas, where a specialist firm will inject it deep underground.  While some would question the propriety of this type of disposal method, Deer Park is in the middle of the most concentrated cluster of oil refineries and petrochemical plants in the U. S., and a little vinyl-chloride-contaminated water way beneath their feet will trouble Deer Park residents not at all. 

 

Someone will have to pay for all the contaminated dirt to be dug up and shipped somewhere else, and so East Palestine is getting more national attention and commerce, although of an undesirable kind, than the mayor and city council ever dreamed of.  While I hope that life returns to whatever passes for normal in eastern Ohio, East Palestine will never be the same again.

 

Sources:  I referred to the following articles:  the NTSB preliminary report on the accident at https://www.ntsb.gov/investigations/Pages/RRD23MR005.aspx, a CNN piece on the report at

https://www.cnn.com/2023/02/24/us/ohio-train-derailment-east-palestine-friday/index.html, a USA Today report at https://www.usatoday.com/story/news/nation/2023/02/24/east-palestine-train-derailment-fish-animal-deaths/11337404002/, a National Review article at https://www.nationalreview.com/2023/02/whats-going-on-with-the-ohio-train-crash/, and the Wikipedia article on "Normal Accidents." 

The Pemex Vinyl Chloride Plant Explosion

Unless you work in the petrochemical industry, you have probably never been near the substance called vinyl chloride.  It is a chlorinated hydrocarbon that is made when one of the four hydrogen atoms in the compound called ethylene is replaced by a chlorine atom.  On the other hand, unless you live in a house whose plumbing is all more than forty or so years old, you probably use products made with vinyl chloride every day.  Polyvinylchloride (PVC) pipes are used in the plumbing of nearly all new residential and business construction, and about 40 million metric tons (units of 1,000 kg) of PVC plastic were made in 2013.  But all PVC pipes were once the toxic, flammable liquid called vinyl chloride, and that is what may have got loose at the Pemex chlorinate 3 plant in the Gulf Coast city of Coatzacoalcos, Mexico last Wednesday, Apr. 20.  The resulting explosion and fire killed at least 28 people and injured over a hundred, with more still missing as of today.

Besides the immediate human tragedy, this accident raises important questions about the safety record of the state-owned petroleum company Pemex.

At this writing, little is known about the cause of the blast.  Coatzacoalcos is a town at the very southernmost tip of the Gulf of Mexico, in the Mexican state of Veracruz between central Mexico and the Yucatan Peninsula.  It is one of the main export terminals for Mexican oil and is a logical location for a vinyl-chloride plant, since its manufacture requires large quantities of the petrochemical ethylene.  The chlorinate 3 plant is a joint venture between Pemex and a PVC-pipe manufacturer called Mexichem. 

As with many petrochemicals, vinyl chloride is hazardous in several ways.  If released into the air, it evaporates into a dense vapor and can catch fire if a source of ignition such as an automobile engine is nearby.  Worse yet, the products of combustion are themselves hazardous:  hydrogen chloride (which when dissolved in water makes hydrochloric acid), and phosgene, which was used as a poison gas in World War I.  Besides the danger of explosion and fire, vinyl chloride is extremely toxic, and causes liver damage in animals at concentrations in air as low as 500 parts per million.  Higher concentrations cause acute illness and even death.  Because of these hazards, vinyl chloride is usually stored in double-walled containers under pressure, with leak monitors that detect low levels of leakage from the inner container before the outer wall is breached. 

It may take months before we can learn exactly what happened at Coatzacoalcos, but it is obvious that a large amount of something flammable got loose.  Some reports mention a strong odor of ammonia, which could be from refrigeration machinery used in process cooling operations in the plant.  Whether or not vinyl chloride itself was released, the high death toll says several things about this accident.

First, one can ask why there were so many people in a hazardous area.  The trend in modern petrochemical operations is to reduce staffing to the point that in emergencies or during strikes, an entire plant can be operated safely from one central control room.  Although this is speculation, it is possible that Pemex, being owned by the Mexican government, has adopted a different policy and relies more on hands-on operators in its plants as a way of increasing government-paid employment.  Whatever the reason, Pemex's safety record is not good.  News reports of this accident relate that in 2012, 26 people were killed in a natural-gas facility owned by Pemex and in 2013, an explosion in Pemex's Mexico City facilities killed 37 people. 

Next, what kind of safety culture does Pemex have?  To run a complex petrochemical plant without accidents is a monumental task, and many safety priorities are expensive, in the sense that they take resources which otherwise could be used to enlarge the firm's bottom line.  With the recent crash in oil prices, there are reports that Pemex is cutting expenses, and this latest accident raises the question of whether safety has been sacrificed to budget considerations.

Finally, there is Pemex's status as a state-owned enterprise.  I am not familiar with Mexican law, but it is quite possible that it is either statutorily or practically difficult to sue Pemex.  Also, Pemex may be self-insured rather than purchasing hazard insurance on the open market.  Both of these factors, if true, remove two of the greatest incentives private firms have to run their operations safely:  fear of lawsuits from injured parties and financial pressure from private insurers to run a safe and low-claims operation.  Without such incentives, Pemex management has only its own integrity to rely on for worker safety, and the demands for sustaining profits in the face of falling oil prices may have overwhelmed safety concerns. 

I hope that the investigative bodies in Mexico have all the competence and authority they need, not only to get to the bottom of this tragedy, but to publicize its causes and assign responsibility wherever it needs to be assigned.  Again, the status of Pemex as a state-owned firm may lead to conflicts of interest between state officials who want to make workplaces safer, and other officials who do not want to see a state-owned enterprise called to account.  The loser in such a conflict will be the workers who have the choice of being paid to put their lives on the line in a hazardous workplace, or to go somewhere else and earn even less than the $12,000 US annual salary that was the average in 2005 for Mexican chemical engineers. 

If reports surface in English as to the cause of this accident, it will be interesting to learn whether poor safety practices contributed to it.  In the meantime, my sympathy goes to all of those who lost loved ones or were injured.  And I hope this latest incident leads to a re-evaluation of the entire safety culture of Pemex, which looks like it could use a lot of work.

Sources:  I referred to a Reuters report on the accident at http://www.reuters.com/article/us-mexico-pemex-idUSKCN0XH2N2, an ABC News report at http://abcnews.go.com/International/wireStory/death-toll-28-mexico-petrochemical-plant-explosion-38614458, a Fox News item at http://www.foxnews.com/world/2016/04/21/blast-at-mexico-petrochemical-plant-kills-3-injures-more-than-100.html, and a CNN report at http://www.cnn.com/2016/04/23/americas/mexico-pemex-petrochemical-blast/.  I also referred to statistics on PVC production at http://www.plasticstoday.com/study-global-pvc-demand-grow-32-annually-through-2021/196257501821043, a salary survey for Mexico at http://www.worldsalaries.org/mexico.shtml, and the Wikipedia articles on vinyl chloride and ethylene.