What Price Prosperity? The Watson Grinding & Manufacturing Explosion

People living in northwest Houston were awakened early Friday morning, Jan. 24, by a tremendous explosion.  A dramatic doorbell-camera video taken from a nearby neighborhood shows a brilliant flash followed by a rising fireball, and then the camera is knocked off its mountings by the arriving shock wave. 

The explosion demolished much of Watson Grinding and Manufacturing, killed two workers, injured about 20 people, and damaged some 400 homes and other structures nearby, 35 of them seriously. 

Investigators from the U. S. Bureau of Alcohol, Tobacco, and Firearms determined that the cause was likely a spark that set off propylene gas leaking from a 2,000-gallon tank, which was later secured by HazMat crews.  The family of one man killed in the explosion has filed a wrongful-death lawsuit, and Harris County has filed suit on behalf of its residents because it claims the firm failed to exercise due care to protect the public.  

Chemical explosions and fires are nothing new to the residents of Greater Houston and the coastal region near it, which has one of the largest concentrations of refineries and petrochemical plants in the world.  The things you can make by tormenting hydrocarbons and other materials with extreme heat and pressure are valuable to the world's economy, and so a lot of money goes into building plants and equipment that necessarily involve dangerous materials and processes.

At this point it is rather speculative to ask what Watson Grinding and Manufacturing was doing with all that propylene.  The most likely answer is that they were using it as a substitute for the even more hazardous acetylene in welding operations and other applications requiring lots of gas-fueled heat, such as heat treating.  Propylene is a gas at room temperature, but like other light hydrocarbon compounds, it can be compressed into liquid form, and that is probably how it was stored in the tank.

One news report points out that any facility where more than 10,000 pounds of propylene are stored has to conform to certain reporting requirements, which Watson Grinding and Manufacturing apparently failed to do.  By my calculations, 2000 gallons of the stuff weighs just about exactly 10,000 pounds, so they may have squeaked under the wire on this one.  Regardless of such reporting, it's obvious that not only did a serious propylene leak occur, no alarms were set off by gas-leak detectors, which these days are not that expensive.  The two employees killed were in the facility's gym, exercising before a work day they never had.

Did these men, who were probably glad to have reasonably well-paying manufacturing jobs, deserve to die?  I can't imagine anyone saying "Yes" to that.  Yet they knew, or may have known, that the stuff they were working with was dangerous, and now and then things go wrong even in the best-run facilities.  A society can be judged by the way it deals with clear cases of injustice, and many industrial accidents fall into that category.

The people who own and/or operate the facility rarely spend much time on the shop floor, exposed to the hazards that they have created.  The people who are injured are killed are either low-level operatives or sometimes just innocent bystanders who could afford only the kind of housing you find in the vicinity of manufacturing districts.  The days when factory owners would build a mansion next door to the plant are long gone. 

We don't have to imagine an alternative universe where regulations on manufacturing would be so tight that hardly anyone, down to the lowliest worker, would be at risk of injury or death.  We have only to look to places such as Amherst, Massachusetts, where I worked for many years.  The regulatory and civic environment was such that anyone wanting to run a plant offering hazards more serious than a paper cut had to flee to another location, such as Sunderland or Hadley.  If some dictator (I won't say anything about the current candidates for presidential nominations) managed to implement Massachusetts-style federal regulations on the whole country, including Houston, why, Houston would be a much safer place to be.  It would also turn into a ghost town, or large sections of it would, because the thing that has already happened to a great deal of manufacturing activity in the U. S. might well happen to the petrochemical and refining industries and all their ancillary commercial infrastructure as well:  it would move offshore to places less hostile to hazardous commercial activity.

This is not to set up a false two-way choice between prosperity and death for workers on the one hand, and third-world poverty and safety on the other hand.  There is a third way, one that allows for dangerous manufacturing processes, but with due attention paid to the hazards involved. 

To their credit, most of the firms doing hazardous manufacturing manage to keep their workers reasonably safe most of the time.  If factories blew up every day, it wouldn't be news.  Still, every explosion reveals a failure of attention:  attention to what might go wrong and diligence in stopping it from going wrong before it gets too far. 

In the coming months, investigators and lawyers will find out a lot about how Watson Grinding and Manufacturing dealt with these problems.  The most important "machinery" in a plant is invisible:  it's the network of minds and human relations that keep the place going while enforcing a culture of safety, and back up that culture with needed resources—or not, as the case may be.  It's obvious that something went wrong:  a leak that began small got bigger, a leak detector that should have sounded the alarm was malfunctioning or not purchased in the first place, and an unfortunate combination of circumstances culminated in the tragedy caught on the doorbell camera. 

The word "love" is rarely brought up in discussions of engineering ethics, but in the proper context, it provides the foundation for good corporate and industrial behavior.  Here's a question that those in charge at Watson could ask themselves.  Take someone you love—a son, daughter, spouse—and answer this question:  would you want your beloved to work at any job in your plant?  For years?  If not, why not?  The answer to those questions can motivate improvements that could prevent things like the explosion at Watson Grinding and Manufacturing in the future.  But only if they are asked, and answered in the right way, with actions as well as words.

Sources:  An Associated Press report on the explosion was carried by numerous outlets, including the Raleigh (NC) News & Observer at https://www.newsobserver.com/news/business/article239855223.html.  I also referred to reports by KPRC Houston at https://www.click2houston.com/news/local/2020/01/31/harris-county-injured-employee-sue-owner-of-watson-grinding-and-manufacturing-after-explosion/

and the Houston Chronicle at https://www.houstonchronicle.com/news/houston-texas/houston/article/What-we-know-about-company-west-explosion-gessner-15000960.php

Arkema's Crosby Nightmare: The Price of Ignorance

If you lived within three miles of a chemical plant where dangerous substances were being made or handled, maybe you wouldn't want to know all the details.  But I bet you'd like first responders in the area to know what was there so they could take appropriate actions if anything went wrong. 

Well, Texas is a good place to live in many ways, but about 3,800 people living within a 3-mile radius of the Arkema chemical plant in Crosby, Texas probably wish they lived somewhere else right now, that is, if they haven't already evacuated because of the record-breaking floods from Hurricane Harvey.  Because several refrigerated trailers parked at the plant are full of chemicals that must be refrigerated to keep them from exploding.  And as the plant flooded shortly after Harvey hit, the power went out, the trailers started warming up, and one of them has gone up in flames already, sending noxious smoke into the neighborhood and forcing 18 first responders to seek medical attention.  And beyond a few general statements from the plant owners about organic peroxides, the public still doesn't know what is in those trailers.

Here's what apparently happened, as I have gathered from news reports. 

Arkema is a multinational chemical-manufacturing conglomerate based in France.  Its Crosby plant is a few miles northeast of the center of town on U. S. 90, and Crosby is northeast of Houston.  The setting is suburban, not really rural, as the 3,800 people within a 3-mile radius can attest. 

Texans are used to chemical plants.  They provide jobs and tax revenues, and while the smells and other hazards associated with chemical plants are drawbacks, the extreme safety precautions taken by most plant operators mean that millions of dollars' worth of chemicals are produced every day in the state without incident, under normal circumstances.  But Hurricane Harvey was anything but normal.

Organic peroxides are extremely reactive chemicals that are used in the polymerization of plastics, among other processes.  While I am no chemist and don't know any more about them than any other random resident of Crosby, I can well believe that some of them are so reactive that you have to keep them cooler than room temperature or else they will decompose violently, leading to an explosion.  Handling such stuff is a challenge, naturally, sort of like shipping frozen fish around, except instead of spoiling if it warms up, it blows up in your face.  So the plant no doubt has a lot of refrigeration machinery to keep its processes cold enough to preserve the nasty stuff, and refrigerated semi-trailers to take it where it needs to go—namely, other chemical plants that are equipped to keep the chemicals cold until they are used. 

All this has gone on up to now without any major incidents, although Arkema has reportedly been cited by regulators several times in the past for safety infractions.  Then last week came forecasts that Harvey, which was only a tropical depression as late as the Tuesday before it struck, was heading toward the Houston area.

The Arkema operators apparently decided that they ought to shut down the plant and move the existing stock of explosive chemicals off site in trailers.  So at some point before the hurricane hit, they loaded nine refrigerated semi-trailers with volatile chemicals that needed to be kept cool, and connected the refrigeration machinery to the local power utility, which was backed up by emergency power onsite. 

A skeleton crew of 11 stayed through the storm, making sure the power was still on to the trailers and switching to emergency power generators when the local utility power failed.  Then the water started to rise, and on Tuesday Aug. 29, the crew was ordered to evacuate, leaving the trailers behind.  As of today (Sunday, Sept. 3) one trailer has exploded, and the others are expected to go at any time.

At that point, one can question why they didn't take the trailers with them.  A number of reasons come to mind:  (1) they didn't have enough tractors (trucks) to haul them out, (2) the flood waters were so high that it might not have been possible to drive away from the plant in such heavy vehicles, (3) the prospect of dragging potentially explosive stuff all over flooded Houston was worse than leaving it there.  For whatever reason, the crew left the chemicals behind, and shortly thereafter Arkema officials announced that within a few days, the chemicals would of a certainty explode and make quite a mess.

An article in the Austin American-Statesman raises the question of why the contents of the plant have not been made public.  Every such plant has to file what's called a Tier II report detailing the chemicals made or used with the U. S. Environmental Protection Agency.  But under current law, it's not easy to gain access to that report.  You have to go to special reading rooms in Federal buildings and you can't photocopy them.  After the 2013 ammonium-nitrate explosion in West, Texas that killed more than a dozen people, the Obama administration proposed requiring the Tier II reports to be in a user-friendly format more widely available to the public.  But manufacturers and Texas regulators opposed this proposal, saying that such information could be used by potential terrorists.  And the new EPA administrator under the Trump administration, Scott Pruitt, has agreed to delay the change by at least two years. 

I said it after West and I'll say it again.  It is stupid that a Tier II report, or something like it, is not made available to first responders near any plant which they might reasonably be expected to respond to.  If you can't trust your local firemen to keep a secret, who can you trust?  And to me, the terrorist excuse sounds phony.  The more likely reason companies don't want Tier II reports released to the public is either out of concerns that competitors will use it, or that environmental protest groups will use the presence of certain chemicals to bring pressure to bear to shut the plant down. 

These concerns are legitimate, but they do not outweigh the needs of those sworn to protect the public from harm, to know what they are up against. 

So far, nobody has died as a result of the Arkema plant explosions.  But there are more trailers waiting to go off, and we still don't know what's in them.

Sources:  I referred to reports on the Arkema explosions and hazards that were carried by Houston TV stations at http://abc13.com/arkema-plant-explodes-after-power-loss/2366889/ and https://www.cbsnews.com/news/flames-erupt-at-arkema-chemical-plant-flooded-by-harvey-in-crosby-texas/.  The Sept. 2 print edition of the Austin American-Statesman carried an article by Jeffrey Schwartz entitled "Information scarce on chemical plant blasts," on p. A11.

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. 

The Disaster in West

Anyone who drives along Interstate 35 in Texas between Waco and Dallas or Fort Worth will pass through West, a small rural Texas town with a Czech heritage that was known, at least until last week, mainly for the pastries that you can buy at a bakery right next to the Interstate.  It would not have surprised me to learn that a distributor of fertilizers to local farmers operated on the east edge of town, nor that one of the kinds of fertilizer sold by the dealer was ammonium nitrate.  But when I learned of the tremendous explosion that killed at least 14 people, injured hundreds, and destroyed a good fraction of West’s built environment last Wednesday evening, April 17, my sadness was tinged with the knowledge that in warehousing large quantities of ammonium nitrate fertilizer, the firm was taking a chance that such a thing could happen.

Ammonium nitrate is a curious chemical.  A “molecule” consists of an ammonium ion (four hydrogens arranged around a nitrogen) with a positive charge and a nitrate ion (a nitrogen atom surrounded by three oxygen atoms) with a negative charge.  At room temperature, it is a solid, but its constituent elements are all gases.  And the only thing holding it together are the opposite charges retained by the ammonium and nitrate ions.  When heated gently in an open container, it breaks down into nitrous oxide (laughing gas) and water.  But when it is in contact with easily oxidized materials, such as the fertilizer urea or even some metals, heating can cause it to release oxygen, which greatly increases the heat of the reaction and can lead to a fire.  When confined by walls or even the pressure of a high stack of the material itself, burning ammonium nitrate can self-detonate.  A detonation is an explosive shock wave that travels at very high speed through a volume of material, and differs from burning as traveling by jet aircraft differs from walking.  This is apparently what happened a little after seven in the evening at the burning warehouse in West.

A back-of-the-envelope calculation of the power of the resulting blast can be done by beginning with an aerial view of the fertilizer plant before the explosion, which is still available on Google Maps.  Comparison with views of the devastated explosion site indicate that the explosion was probably centered in a large, flat warehouse building that appeared to be one story high and measured about 60 feet by 110 feet.  If we assume it was packed to a height of eight feet with ammonium nitrate (not an unreasonable assumption as distributors stock up for the summer growing season), the total mass of chemical in that building could have been as much as two thousand tons.  Pure ammonium nitrate has about a fourth of the energy content per pound as TNT.  Still, given these rough assumptions, if the whole mass went off at once, which it appears to have done, the force of the explosion could have been as great as a thousand tons of TNT, or one kiloton.

You may have run across the word “kiloton” in reference to nuclear explosions.  While there were fortunately no nuclear weapons or radioactive materials involved in the West explosion, the nuclear weapon dropped on Hiroshima at the end of World War II had a yield of only about 16 kilotons of TNT.  So what happened in West was one-sixteenth of a small nuclear bomb, in terms of destructive power.  No wonder it showed up on seismographs as a magnitude-2 earthquake.

If ammonium nitrate is so dangerous, why isn’t handling and use of it more regulated?  That’s a good question.  The Wikipedia article on ammonium nitrate notes that in 2005, Australia passed a Dangerous Goods Regulation law which requires a license for the sale or use of the material.  But if even licensed users store huge quantities of the stuff in places where it can catch fire and explode, licensing would not prevent disasters such as the one that happened to West last week, or Texas City in 1947, or over twenty other occasions since 1916 listed in a separate Wikipedia article devoted to ammonium nitrate disasters. 

Chemical companies that deal routinely with explosives know how to handle these materials so that when they explode, the explosions are limited to a small area that is sacrificed in order to protect the rest of the property and lives involved.  You simply restrict the amount of explosive allowed in one place to a maximum amount that you can afford to blow up, and then physically isolate it from all other concentrations of explosive in a series of small bunkers.  If the fertilizer stored in the West Fertilizer Company plant had been dispersed in this way, perhaps one of the small storage areas might have blown up, but with sufficient earth-berm isolation and other precautions, the explosion would not have spread.

That is small comfort for the survivors in West.  And as a practical matter, you can handle ammonium nitrate in an ordinary way without special precautions, as it is done thousands of times each year around the world, and most of the time, nothing bad will happen.  If the West firm had been required to invest in the additional storage facilities needed to treat ammonium nitrate as a true explosive, it would have gone out of business for sure.  (News reports indicate the firm nearly went bankrupt a few years ago and was rescued at the last minute by the present owner.)  So we face the dilemma of either requiring a huge investment in safety facilities on the part of fertilizer manufacturers and retailers everywhere to prevent disasters like West, or we leave things as they are and wait for the next one.

A compromise solution might be the rigorous training of anyone who deals with ammonium nitrate, enforced by a licensing law similar to the one on Australia.  This would include mandatory evacuations based on scientific calculations of a worst-case explosion whenever a fire occurs near large quantities of the stuff.  While regulations like this would not have prevented the damage caused by the West detonation, it could have reduced the death toll. 

Our thoughts and prayers are with the residents of West, whose tragic experience may lead to changes that at least mitigate the dangers involved in dealing with ammonium nitrate in the future.  

Sources:  I referred to the Wikipedia articles “Energy density,” “Ammonium nitrate” and “Ammonium nitrate disasters” as well as Google maps of the vicinity and photographs in various publications of the disaster site, and the book The Science of High Explosives by Melvin A. Cook (Reinhold, 1958).