Part 1. What is Nylon and How it’s Made. 

1. Originally designed to replace silk in 1938. Silk is extremely strong and durable but it’s handmade by a worm and mass production of the stuff takes forever. 

2. At its inception during WWII, nylon was produced by chemical titan, DuPont as a fully synthetic fiber that is immune to mildew, solvents, and could be structured in a variety of different ways for a multitude of applications. 

   1. Originally intended to replace silk parachutes

   2. Took off with women during the 40s for pantyhose and various other articles of clothing (today 52% of clothing is made from polyester with only 5% containing nylon, but in the 40s and 50s, nylon was super popular for clothing)

   3. Today, nylon is found in:

      1. Automotive industry- ability to resist wear and tear

      2. Industrial components- same as automotive industry

      3. Packaging- because of its ability to resist impacts. 

      4. Consumer goods and electronics 

      5. Medical and safety equipment- harnesses, safety vests etc. the body’s immune system doesn’t recognize nylon. 

   4. In other words, Nylon is found everywhere. It’s not as common in the things we wear, but it's super common in just about everything else around us. 

3. The advent of nylon stemmed from the synthetic fiber revolution of the 20s and 30s. 

   1. The first half of the 20th century saw the most scientific growth in humanity ranging from chemistry, physics, astronomy and engineering to medicine and biology.

      1. Having a world war in the 1910s really helped with technological advancement, because humans are totally fine living in the stone age, but if technology can help kill your enemies faster and further away, then we’re all for it!

      2. An example of this is the chemical warfare used in WWI. The toxic weaponry in WWI like mustard gas, phosgene, and chlorine were produced in converted pain factories that used the latest and greatest of large scale chemical production available. 

4. One such field of study in the early 1900s was the development and understanding of polymers.

   1. I’m not going to bore you to death with a deep lesson on what polymers are but I think I can give you a basic idea. 

   2. The soft squishy stuff that makes up a human being or most other living multicellular organisms on earth are made of proteins. 

   3. Proteins take organic elements like hydrogen, nitrogen, carbon, oxygen and a few other elements and arrange them into long chains called macromolecules. 

      1. Macromolecules can be combined together over and over again and we can make some cool things like silk, cotton thread, and human hair. The downside is that we need to farm, harvest, and manipulate these protein chains within the environment of living organisms. 

      2. So if you need to make a 300 square foot parachute out of silk, you’ll need hundreds of thousands of silk worms, eating, and producing silk 24/7 for god only knows how long. 

      3. That’s super time consuming and a huge resource suck… 

   4. This is where polymers come into play. Polymers are long chains of macromolecules like proteins, but they are synthetic, or man made. 

      1. Polymers involve very non-organic elements and compounds to make their chains. The benefit of using these compounds is that you can mix everything in a jar and poof! You have a polymer like nylon. 

      2. Some of the chemicals you find in polymer chemistry:

         1. Ethylene

         2. Propylene

         3. Polyethylene

         4. Polychloroprene

         5. Polystyrene

         6. Hexamethylenediamin

         7. Adipic acid

         8. Caprolactam

         9. Cyclohexane

         10. Hexamethylenediamine and Dodecanedioic acid

      3. What do all these have in common? None of these by themselves should ever be consumed by any living critter including humanoid critters. None of these are excreted by a living thing. Most of these chemicals are INSANELY FLAMMIBLE if not EXPLOSIVE!!!

5. Making macromolecules the “natural way” involves pee, poo, and farts as a byproduct. Making macromolecules via the synthetic method involves, mega factories, with giant vats of toxic / flammable chemicals heated to ungodly temperatures and everything is kept in check by thoughts and prayers. 

   1. Once we get past the notion that synthetic fibers in a factory can be detrimental to one’s health in the manufacturing process as well as explosive, the final product can be very useful. 

   2. So yes, a factory making polymers like nylon are ticking timebombs, but they can produce a high demand product by the ton everyday… just as long no one lights a match.

Part 2. Where and why to build a massive highly flammable chemical factory. 

1. Real brief history of how the Flixborough chemical factory came about. 

2. Let’s go back to WWII. Germany had an air force that could get to England at any time and do a lot of damage. So Churchill  and crew decided to move a lot of production out to the countryside. 

3. England needed nitrogen to make everything from bombs and explosives to preservatives. 

4. So the plan was to build stuff out on the countryside where the land was abundant, a bit further away than London and very unassuming to the Luftwaffe. Hence Flixborough. 

   1. Flixborough is about 30 to 40 miles south of Leeds and about 100 miles North of London. Not sure if this helps give an idea of where Flixborough is, but it’s easy enough to find on Google Maps. 

   2. For the duration of the war, Flixborough produced a lot of nitrogen based chemicals such as ammonium nitrate, N2 in general, and a bunch of other things until the Luftwaffe found the site, correctly assumed it was a collection of factories, and blew the crap out of it in 1938. 

5. After WWII, the Flixborough region remained a popular place to manufacture nitrogen compounds where they could get the necessary ingredients from surrounding steelworks sites.

6. In 1962 a company called Nypro was founded in Clinton, Massachusetts and quickly became a world leader in plastics and synthetic fiber production. By the time of the contract for the Flixborough location (1965), Nypro had already developed a UK division with the very innovative name of Nypro UK Division.  

7. This region seemed like a great place to build the new Nypro factory since it was so remote, and yet there were enough people living there to sustain employment, and there was substantial infrastructure to transport goods to and from Flixborough. 

   1. The plan for Nypro UK was to set up this Flixborough chemical plant to produce a substance called “caprolactam” which is a key ingredient to making nylon. 

8. I am pretty sure that caprolactam is a substance that has its own toxic properties and it may be flammable as well. But for the purposes of this dumpster fire, we’re going to be looking at what goes into making the stuff. 

   1. To make caprolactam, you need lots and lots of “cyclohexane.” You don’t have to be a chemist to look at the word cyclohexane and immediately pick up a bad vibe. Somehow when we look at this word, “holy crap this stuff sounds flammable!” comes to mind and if that is the case, then your intuition is spot on. 

   2. And this factory was going to be handling thousands of gallons of the stuff on a daily basis. 

9. This is what leads me to believe the real reason why Nypro (with Parliament's blessing) chose Flixborough… the entire region was expendable. 

   1. If there was a disaster and everything went “tits up” as the Brits would say, then a relatively small community would be affected. If the tits went up in central London, then there is no telling what would happen or what the damage would be. 

   2. I’m sure that the public was told that Flixborough would be out of sight / out of mind to communist enemies, and the region was suitable for the production of caprolactam based on its history etc, etc.

      1. But the age-old philosophical question from 18th century George Berkeley remains: if a chemical plant processing thousands of gallons of highly flammable fluids ignites and goes boom and erases an entire community from the English countryside and no one is alive to hear it… then does it actually make a sound? 

Part 3. Inside a state of the art chemical plant.

1. The Nypro Flixborough chemical plant started construction in 1965 and was completed by 1967. 

2. To make things a bit more confusing:

   1. It was built by Simon Carves with Stamicarbon of the Netherlands, which was a subsidiary of DMS and Humphreys & Glasgow and run by Ambrose Congreve…

   2. … so yeah I have no idea just who is responsible for this plant… I’m not even sure who was responsible for when things went wrong because who knows who was even running things.

3. However, the chemical plant was designed from the ground up to be a state of the art facility with all the recent safety protocols, cleanliness, and overall aesthetics. 

   1. For hire signs went up in the surrounding communities for pretty much all positions and many were drawn to the cleanliness and organization of the plant. Some commented on the futuristic appeal. 

   2. The new hire signs were asking for a myriad of engineers ranging from chemical, electrical, and mechanical not to mention dozens of technicians and hands who would operate the facility. 

   3. In total, up to 550 people were hired to work at the plant. 

4. Here is the basic rundown of how the factory work:

   1. Everything surrounded and supported the function of 6 massive reactor tanks. Each tank was 16’ 4” tall (5 meters) and 11’ 6” in diameter (3.5 meters) and were capable of handling 20 tons of material or cyclohexane. 

   2. The 6 tanks were positioned right next to each other, however they were staggered in descending height. So tank 2 sat 14” below tank 1 and tank 3 sat 14” below tank 2 etc. 

   3. Each tank would be connected with a pipe about 28” inches in diameter. 

   4. Basically, 20 tons of cyclohexane would be pumped into tank number 1 and then heated to 155 degrees Centigrade at 116 psi of pressure. Once up to temp and pressure, massive amounts of O2 would be pumped into the tank and from what I understand the environment turns the cyclohexane into a vapor of sorts where it would rise up and transfer to the next tank via the 28” pipe where the process would happen again. 

   5. It’s similar to a distillation process, but instead of trying to separate water from alcohol, you’re trying to turn one substance into another and repeat the process so that by the time the caprolactam leaves tank 6, it’s in its purest form. 

5. Now let's do some thought analysis and see what conclusion you can draw:

   1. We have a factory that turns an insanely flammable substance into something else.

   2. To do this we have to pressurize this flammable substance and heat it to nearly 300 degrees.

   3. Then pressurize it to 116 psi to keep it in liquid form. 

   4. Then blast literally tons of pure O2 into the tanks of heated, pressurized, insanely flammable substance.

   5. And pray to god that nothing goes wrong like a leak and hope that no one or a random thing throws a spark. 

   6. Can you guess what the dumpster fire is going to look like when it takes place, based on what the dumpster has been filled with?

6. In terms of operation, the plant worked well (or as wells could be based on witness testimony after the “incident”

   1. It was commented to the news later on that it was a common occurrence to hear fire trucks heading to the plant to put out some sort of a fire. 

   2. It was common knowledge that working in such a place was inherently dangerous, however there were two factors that kept people working there:

      1. 1. The pay was really good. The perks of working in an industry that is in high demand, at the only facility in the country that is producing what the industry needs to function. 

      2. 2. If a catastrophic event took place and the whole plant went up, you would be erased from this plane of existence before you even knew what happened. That was the perspective of the workers. However, the family members including the wives of the workers were under the impression that an explosion would go up into the sky and leave everyone on the ground safe… 

   3. From 1967 when the plant was finished with construction to the first quarter of 1974, the plan worked and was for the most part safe. 

   4. During the work week, the plant would have over 200 men and women working and the weekends had between 70 and 80 men working. 

7. And it wasn’t as though safety was lax during this time either. 

   1. Everyday, workers were searched for lighters or anything that could throw a spark. 

   2. Special shoes would have to be worn that negated the collection of static electricity. 

   3. Even clothing was inspected to make sure it was the right kind to have inside so that a shirt wouldn’t throw a spark. 

8. The only issue was that the pant needed to produce 70,000 tons of caprolactam a year. However, less than half of that was being manufactured and the pressure (no pun intended) was mounting to get that yield as close to the quota as much as possible. 

9. Everything was going to change starting in March of 1974.

Part 4. The Crack to End All Cracks

1. On March 27, 1974, during a routine inspection of the 6 reactor tanks, a massive crack was discovered on tank #5. 

   1. As in all things, size is subjective depending on who you ask, however, when dealing with a 16’ 4” tall tank with 20 tons of explosive solution, ANY crack is going to be too big. 

   2. However, the crack that formed on tank #5 was 28” long! I don’t care who you ask, 28” of anything is too big…

   3. Who knows if the crack went all the way through the tank, but given the contents, it was decided to shut down the entire operation.

      1. This was a sound idea. Even though the emphasis was on increasing production at all costs. Management understood that something like this crack could be a deal breaker for the entire facility if it went unaddressed.

   4. The issue wasn’t management leaving a problem unaddressed, it was how they addressed the problem that made things go sideways. 

2. So the whole facility was shut down and evacuated on the 27th. Cool. The discussion quickly turned to what to do about the cack. 

   1. Option 1. Stay shut down until a replacement tank could be manufactured and installed (keep in mind, all tanks of this size are pretty much custom jobs. It’s not like you can pick one of these things up at your local hardware store. So this could take weeks if not months to complete. This would be a 100% guarantee that the problem would be solved safely, but management nor the workers wanted to be shut down that long. 

   2. Option 2. Patch up the current tank. It would be the quickest option, but everyone knew that it would be the dumbest for a multitude of reasons. 

   3. Option 3. Run the plant without tank #5 and just bypass it so the caprolactam process would go from tanks 1 to 2 to 3 to 4 and then to 6. This way the plant could stay up and running and a new tank #5 could be manufactured and replaced in time. 

3. Option 3 was heralded as the best option and planning and work immediately began to disconnect tank #5 and make a makeshift pipe that would go from tank #4 and descend 28” down to tank #6 (remember, the tanks are arranged in a descending order). 

4. A repair of this magnitude needs a lot of careful planning and measuring and forethought and execution. So the plans were written out in chalk on the floor of the plant. 

5. Management did bring in every expert on the payroll to oversee and execute the repair. On hand they had the following:

   1. A few chemical engineers

   2. An electrical engineer who didn’t have a degree but I guess he knew more than the average layman. 

   3. A plumber (check out images of the plant before and after the disaster on thedaysdumpsterfire.com to see why a plumber would be in such high demand).

   4. A mechanical engineer… still a vacant position at the time of these events. 

Part 5. The McGuyver Repair Job

1. So based on the above roster of qualified repair folks, here is how the repair went down. 

2. The main crux of the repair centered around the pipe that was going to connect tanks #4 and #6. The normal pipe connecting each tank to each other is 28” in diameter. However, no one could find a similar sized pipe that could span the 15’ or so between 4 and 6. 

3. The biggest one they could find was 20” in diameter so they figured that would be good enough. 

   1. The vacant mechanical engineering position would be screaming right now. 

4. Since tank 4 was around 28” higher than tank 6, to connect the two tanks the 20” pipe was cut into 3 segments. Two long pieces and one piece in the middle that was going to be cut at an angle at either end. When it was welded together the pipe was going to have what is known as a dog leg. This means that when everything was welded it would come out of tank 4 for a few feet, angle down at a 45 degree angle to account for the width of tank 5, then level out again to attach to tank 6. 

5. To account for heating and cooling and the subsequent expanding and contraction of all the metal of the pipes and tanks, a bellows adapter was put on either end of the dog legged pipe to connect it to tanks 4 and 6. The bellows would allow for some flexing between tanks without putting undue stress on the repair job. They used the same exact bellows that connected tanks 1-4 so everyone figured it would be good enough. 

   1. Now the vacant mechanic engineering position would be losing his mind now based on all the jerry rigging that was going on… 

6. To really make sure things were secure, a 2x5 frame was constructed around the pipe connecting 4 and 6 to reduce the weight of the 20” pipe repair job from over stressing the bellows connectors and snap off.

   1. Insert vacant mechanical engineering position throwing up his hands in exasperation. 

7. Lastly, there were no tests performed on the repair pipe, bellows, or the entire assembly. The whole thing was designed, cut, welded (no experienced welders by the way) assembled, and attached to tanks 4 and 6… WITHIN 30 HOURS!!!

   1. That’s right, everything was slapped together with only a couple certified chemical engineers, a plumber, and supervised by a non credited electrical engineer all without the one person who could see all the red flags from a mile away, the mechanical engineer. 

   2. At this point the vacant mechanical engineering position is contacting his lawyers to protect himself from the fallout associated with this dubious repair. Thankfully there was no mechanical engineer around that could either do the repair correctly, object severely to what was going on, or quit work at literally any other location in England that is safer than what is going on here. 

8. Everything was hooked up by March 29th, slowly the process of manufacturing caprolactam was initiated and without warning, suddenly… everything worked!

   1. That’s right folks, the McGuyver rigged worked perfectly. No real leaks were detected and nothing had exploded. 

   2. This was a remarkable repair and everyone who worked on it patted each other on the back and celebrated the idea that a lot of payroll that was going to be spent on a mechanical engineer’s salary wasn’t needed. I’m not sure if that is what they were thinking, but I can imagine that the plant managers were extremely excited that this temporary repair worked perfectly. 

Part 6. Temporary Schempoary! Everything is fine!

1. Take a look at your home or car or anything else that is complicated that you’ve repaired in the past by dodgy means. 

2. How many years has it been that you used electrical tape to cover up that frayed wire? How many gallons of catalytic cleaner have you run through your car to clear out the P0420 code indicating that the catalytic converter isn’t working right? How long was it that you superglued a ripped off button to your shirt vs watching a youtube video on how to sew one back on?

3. Human beings are marvelous engineers. Whether we know what we’re doing or we don’t, humans are notorious for trying to fix things. 

4. However, we often fall into this trap: we intend a repair job to be temporary until it works fine for so long that we say screw it, and promote the repair to a full time permanent repair… 

   1. But how many times have temporary repairs freshly changed status to permanent, have blown up in our faces, often catastrophically? Probably more times than we can count. 

5. The management and crew of the Nypro Flixborough plant discovered this idea the hard way on Jun 1, 1974. 

   1. For months the jank welded, 2x4 supported 20” pipe ill-fitted between two tanks filled with 20 tons of pressurized heated flammable solution worked perfectly. There were no serious issues to report beyond the usual calling out the fire brigade for the ritualist random fire that needed to be put out. 

6. That is until around 4:30pm on Saturday, June 1, 1974 when 72 men experienced what many thought was the beginning of World War III. 

7. Insert Flixborough Clip 2. 

8. The Nypro Flixborough facility that took up 10 to 15 acres of land, comprising miles and miles of piping, tubes, metal structures, office buildings and hundreds of tons of cyclohexane essentially disappeared off the British countryside. 

   1. The explosion was regarded as the largest explosion in peacetime English history.

   2. Over 40 acres of the English countryside had caught on fire which took 10 days to put out. 

   3. The explosion was so massive that it damaged buildings 1 mile radius away from the site and people up to 3 miles away could hear or see what happened and people over 30 miles away heard the explosion. 

   4. 1,800 homes and other structures were severely damaged or completely destroyed as a result. What’s interesting to note is that the closest homes were over 300 yards away and they were pretty much leveled. 

9. Inside the plant 28 men were killed instantly. All 18 men inside the control room that oversaw the reactors as well as pressures and operation of the reactors had died…

10. Another 36 men were severely injured with many now living with permanently disfiguring burns, blindness, and deafness. 

    1. Hop on over to the daysdumpsterfire.com to see before and after pictures. 

11. For days following the incident, the rest of the Nypro roster came out to help look for bodies or anyone who might be alive. All the fire and rescue teams in the country were called out to assist. When a body was found by search and rescue, the workers who volunteered to help out were sent on a teach break to spare them the sight of the corpses for obvious reasons. 

12. Years following the explosion, the communities surrounding the Nypro plant could remember exactly where they were and what they were doing the day of the explosion and the maimed and disfigured survivors around town were constant reminders of what happened. 

Part 7. So What Did Happen?

1. As you can imagine, after the investigation and forensic research and what not, the cause of the explosion stemmed from that janky repair back in March. But how was it that a repair that worked fine for months with no issues, suddenly failed randomly?

2. The best way to explain this dumpster fire is to break things down to sections because so many components failed at the same time. 

   1. The 20” pipe: pipes operate in two main variables, volume and pressure. When an amount of fluid transfers from one volume to a smaller one, then the pressure WILL go up. Conversely, if a fluid exits a pipe of a smaller volume into a bigger one, then the pressure goes down. The 20” pipe was never rated or tested to handle the increase in pressure from the 28” fitting from tank 4 being necked down to 20” for the repair pipe. 

   2. This also ties into the issue with the dogleg section of the repair pipe and the welds. The welds on the outside probably looked ok. However, there was no investigation into how much pressure those welds would have to sustain on top of the pressure increase associated with the decrease in volume. As soon as a pipe needs to change in any direction, the pressure on the bend and subsequent welds skyrockets. All it would take is the wrong kind of welding wire to be used, or a wrong mix of gas and oxygen, or one welding bead being thinner in one part and thicker in another part to fail catastrophically. 

   3. The bellows: they used the same bellows that were used on all the other connects in tanks 1 through 4. The reasoning was that if it worked for those sections, then it would work for this repair. However, the bellows used in between tanks 4 and 6 were the ones responsible for necking the 28” diameter pipe down to 20”. That means the rubber bellows would absorb a brunt of the pressure increase not to mention the heat from tank 4 at 115 psi. 

   4. The 2x4 support structure: this one is pretty self explanatory. Wooden beams flex a lot and that’s on purpose. One of the reasons why houses are built from wood is that wood flexes while still maintaining strength. That makes it so the house can settle into the ground over time and not completely fall apart. It’s the reason why over time you see random cracks on the ceiling or where the walls come in contact with a horizontal surface. But when you’re relying on wood to hold up thousands of pounds of metal transporting hot liquids, it was a matter of time before the 2x4’s would eventually break down. 

   5. Testing: there was no check of the repair prior to installing it. Granted it would have been very difficult and expensive to do, but by today's standards, these sorts of repairs are tested to conditions far exceeding the parameters that the surrounding materials would have to deal with. If the management had taken a week or two to test the repair properly, perhaps there would have been no catastrophic explosion. 

3. But I think there was a problem that superseded the above issues: Money. Like so many decisions resulting in dumpster fires, the revenue stream is the ultimate determiner of how things are going to take place. In the case of the Nypro plant going up, lost revenue and wages was ultimately the thing that promoted the temporary repair to a permanent one. The repair job itself was in fact pretty brilliant and it would have remained that way, if management had used the bought time to replace tank #5 all together instead of relying on it forever. The fear of lost money forced everyone to make ill advised decisions. 

4. However, I think there is another major issue that played a part here that has nothing to do with the plant, the repair, the workers, the managers or even the surrounding communities.

   1. Talks about my experience in CA years ago where there wasn’t enough electricity to go around and many businesses could only work certain days of the week. 

Part 8. The aftermath

1. After weeks and months of sorting through the wreckage and making sure there were no more bodies to be found. Work began on the construction of a new facility. 

   1. Albeit, the new facility was built with way more attention to safety, reliability, and survivability in case of an issue. Today the area looks nothing like the original Nypro facility. 

2. While the chemical plant was being rebuilt, there was a major run on Nylon made items in England. Since all the production of caprolactam came from one location, there was no immediate recovery of nylon production. Yes it’s logistically cheaper and easier to locate all the production of something in one spot, if a devastating event takes place, there is no way to get production up and running again quickly. 

   1. However, I’m sure America and other countries stepped in to sell nylon to England at less than favorable rates…

3. Shockingly, no one was blamed for the incident. 

   1. I think this was tied to the fact that there were so many different entities involved in the designing, construction, and running the whole complex that it was impossible to pin it on any one person. 

   2. I’m not sure how I feel about that, but it beats a witch hunt along with years of expensive lawsuits between entities and innocent people going to jail. 

4. In the end, even in these economic times. Never rely on a bandaid repair to fix a permanent issue. Sometimes you need to bite the bullet to get something fixed correctly because a little extra money now can save ten fold down the road. 

Resources:

https://sewport.com/fabrics-directory/nylon-fabric

https://www.hse.gov.uk/comah/sragtech/caseflixboroug74.htm

https://www.sciencedirect.com/topics/chemical-engineering/cyclohexane

https://www.sciencehistory.org/stories/magazine/nylon-a-revolution-in-textiles/

https://www.theguardian.com/environment/2021/nov/06/clothes-made-from-recycled-materials-sustainable-plastic-climate

https://www.theworldwar.org/learn/about-wwi/spotlight-first-usage-poison-gas

https://www.britannica.com/science/polymer

https://www.pbs.org/wgbh/aso/databank/entries/dt35ny.html

https://www.chemistryworld.com/news/remembering-flixborough-50-years-on-from-one-of-the-chemical-industrys-deadliest-disasters/4019577.article

https://northlincolnshiremuseum.co.uk/discover/flixborough-1974-memories-debra-harding-morris/

https://www.bbc.com/news/articles/c0wwepe5g10o