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Podcast: Lessons Learned From Flixborough 50 Years Later

May 31, 2024
The Flixborough disaster in 1974 resulted in 28 fatalities and significant damage, leading to the introduction of management of change processes, improved asset integrity practices, emphasis on competency management, and enhanced control room safety measures. This landmark incident highlighted the importance of multidisciplinary collaboration and continues to serve as a lesson in process safety.


Welcome to Process Safety With Trish & Traci, the podcast that aims to share insights from past incidents to help avoid future events. Please subscribe to this free podcast on your favorite platform so you can continue learning with Trish and me in this series. I'm Traci Purdum, Editor-in-Chief of Chemical Processing, and as always, I'm joined by Trish Kerin, the director of the IChemE Safety Centre. Hey, Trish, what have you been working on lately?

Trish: Hey, Traci. Well, I've been traveling around again, so the platypus has been with me traveling all over the world, and I've been talking to people about safety leadership more specifically and trying to help them improve their safety leadership and how they can get better outcomes in that.

Traci:  I see your Instagram posts with the platypus. Do folks question you why you're taking pictures of a stuffed platypus?

Trish: I do get some strange looks at times when I all of a sudden reach into my bag and pull out this platypus and position him somewhere and take a photo. I was on vacation once, and I have a little tiny pocket-sized plastic one, and I was in the middle of the Australian Outback, and I was on this tour, and I pulled out my little platypus and I put it down in the middle of the Australian desert and was taking a photo of it, and this other woman on the tour got all excited because she thought I'd found some amazing creature I was looking at, and so she sort of rushed over, almost pushed me out of the way to look at it, and then just looked at me and went, "It's a toy." And I went, "Yeah," and picked it up again and put it in my pocket and walked off. So yeah, you get some strange looks.

Traci: And for people who were wondering what we're talking about the platypus for, Trish wrote a book, The Platypus Philosophy, talking about finding your weak signals, so if you're not familiar with it, you can Google it or go to Amazon and figure out what we're talking about. But for listeners to this podcast, you know the platypus well.

Trish: Yes.

Traci:  All right. Well, today we're going to be looking back. We're on the 50th anniversary of Flixborough. In your latest Stay Safe column for Chemical Processing, you talk about deliberate change, which occurs when you consciously intervene and initiate transformations, and also you talk about creeping change, where systems or equipment slowly deteriorate over time, and you use this as a way to extract lessons learned and apply it to the 50th anniversary of the catastrophe and the explosion and fire that tore through the Nypro plant in Flixborough, U.K., that resulted in 28 lost lives. This disaster occurred on June 1st, 1974. Let's talk about that day and to try and figure out what happened. Can you first tell us what caused the explosion?

What Happened At Flixborough?

Trish: Yeah, so this is a particularly interesting process to follow. So what was happening at this plant, there were six reactors in series, and they were oxidizing cyclohexanone and cyclohexanane through these reactors using air. Now what they discovered at some point earlier that year, around about March time, Reactor Number 5 in that series had a crack in it, and so they thought, "Okay, we've got to take it out of service so we can fix the crack." But what they then thought was, "Well, we can actually do enough oxidation without Reactor 5, so we can put a bypass pipe in." Now the reactors were also set at different heights. They actually fed into each other via gravity, so they stepped down in height as it went through. So Number 5 was quite low in that process, and then obviously Number 6 was even lower. So when they went to join Number 4 and Number 6, they basically just put a piece of pipe in that was almost a dogleg shape with some expansion bellows to allow for some movement, and they bolted in this pipe work, and then they restarted the process again.

Now, they actually ran successfully under that system for a few months when they actually had another leak occur somewhere else. And so they then took the plant down again to repair that other leak, and then on restart up, that dogleg catastrophically failed. That was a twenty-inch pipe, and when that catastrophically failed, it released 30 tons of cyclohexane at about 150 PSI pressure and 150 degrees C, and so that created a massive vapor cloud that then ignited and exploded at that time. So really significant incident. It killed 28 people when it exploded, it injured another 36 at the plant, as well as 53 people outside in the community, and it damaged almost 2,000 buildings in the community around it as well as destroying the plant.

Traci:  That's a huge catastrophe. Were any safety measures or regulations in place? And how did this occur? How could they do that dogleg without having anybody question it?

Trish: Yeah, so this is where it gets quite interesting, that the UK legislative system at the time wasn't the same as what it is today, so there was not a lot of guidance around it. There were still industry standards and there was still manufacturing standards for various different pieces of equipment, like the bellows, and in fact, the bellows were not recommended to be installed in a pipe that wasn't straight. So straight away we had a dogleg pipe with a bellows on each end of it. Now, what had actually happened there is the facility in about the January or so had its mechanical engineer leave, and so there was no mechanical engineer on that site. There were qualified and very competent chemical engineers managing and working on that site, but typically, if you want to talk about pressure in pipework and how pipework responds under pressure, that's when you need a mechanical engineer, because mechanical engineers do pipework design and they understand the pressure loading on pipes and how that can create what we call moments on a pipe. So a moment is it's a way a force is applied to a particular piece of equipment.

So a mechanical engineer would've looked at that dogleg and looked at that design and said, "No, the moment on that pipe is too great. It's not designed for it. It needs better stabilization or a different design," but there was no mechanical engineer there at all. So anecdotally, this piece of pipe was actually drawn up in chalk on the workshop floor and fabricated that way. The connections that it was bolting onto were 28-inch, but they could only find a 20-inch piece of pipe, so they had to reduce the size as well. And so it was a very ad hoc construction, and it only took them about four days to manufacture this piece of pipe and install it, and so it didn't go through any detailed design calculations that you would've expected a pipe to go through, and there was no one to recognize that it needed to go through those detailed calculations because they didn't have the right competency at the facility. There's no mechanical engineer there.

How the Flixborough Disaster Influenced Safety Standards

Traci:  Now not having the right competency, not having the mechanical engineer to look in and say, "Listen, this chalk design is not sound," how did all of this influence changes in industrial safety regulations and practices? Obviously, looking back at that and moving forward. How did this influence change?

Trish: So Flixborough is the incident that we credit with the creation of management of change, the focus whereby we do a detailed assessment of a change that we're about to make, whether it's a permanent or a temporary change. So in this instance at Flixborough, it was a temporary change that always intended to put Reactor 5 back. So now we have a management of change process that we use throughout the world. We still don't always get it right, but we at least have a process that we can understand and follow, where we have to identify what the change is, consult with subject matter experts, and do appropriate risk assessments to make sure that the change that we are doing is safe, it's not introducing any additional hazard, or if it is, we are managing that hazard to an appropriate level, and then also making sure if it is a temporary change, that we take it back safely again. So certainly management of change has been a significant development out of Flixborough.

It also caused us to focus more on asset integrity and understanding why the leaks occurred, understanding the importance of primary containment a little bit more, a bit focus on that. Competence and capability management, the fact that we do need to understand that different disciplines contribute different things to safe design and operation of a plant. So it's not just chemical engineers, or just mechanical engineers, or just electrical engineers, or even just civil engineers. We actually need all of us working together to deliver the safer outcomes for our facilities. And another really important lesson that came out of Flixborough was the placing of control rooms. Now, sadly, we've seen this happen in a number of other incidents around the world. If we think of Texas City refinery, where there was the demountable trailer where people were gathered when the isomerate tower was being refilled and restarted.

So the focus that we now try and remove people and control rooms from in the middle of the process, and if we can't remove them from that, then we actually armor and strengthen those control rooms so they become a safe haven in the event of an explosion. I actually had the privilege many years ago to work in a facility that was the first major facility constructed by the company ICI at the time, following the Flixborough incident that had occurred, and that facility was built in the 1970s in Australia, and it had a blastproof control building.

Emergency Response and Cleanup

Traci:  So plenty of lessons learned. I know that Flixborough has been analyzed and talked about so many times, and through tragedy, we find ways to help people stay safer, so at least we are going forward with that. Let's dial back a little bit and talk about the challenges faced during emergency response and cleanup efforts with Flixborough.

Trish: Yeah, so it was an absolutely massive amount of destruction that occurred at that particular facility. As I said, it completely flattened effectively the whole facility, but it did enormous damage to the neighboring houses and town of Flixborough. Something like 1,800 houses and almost 200 businesses were damaged as a result. Some of those houses were damaged so much that they had to be demolished. The fire that burned burned for three days over 10 acres. This was a massive, massive fire that took a lot of resources to try and bring under control, and managing, dealing with not being able to effectively shut anything down because the entire facility was damaged beyond repair at that point, so very significant emergency response activity.

I think what was most interesting is that because of the legislative structure at the time, there was actually no legal proceedings following this incident at all. It was settled out of court and there was no prosecution associated with it, yet it is one of the most substantial and significant incidents. I mean, it was not as significant as Bhopal, obviously, which we will have the 40th anniversary of in December this year, but it was at that time the most significant incident that had occurred other than some of the ammonium nitrate explosions that had occurred in previous decades.

Traci:  How does Flixborough compare to other major industrial accidents in terms of its impact and lessons learned?

Trish: So as I said, it's not as big as Bhopal. Bhopal killed thousands and thousands of people when it occurred. Mexico City BLEVE that also is having its 40th anniversary later this year killed hundreds and hundreds of people when that occurred. So in terms of loss of life, it's certainly nowhere near some of the biggest ones we've seen and, as I mentioned, some of the previous ammonium nitrate incidents, things like Texas City in the '40s, when they had the ammonium nitrate ship explode, and Oppau in Germany. So massive incidents had occurred previously as well.

But it's the one that really has, it created a significant focus. It was interesting at the time in the UK that they were debating in Parliament a new law for health and safety, and so when Flixborough occurred, a lot of lessons were taken out of it and put into the new laws. So it created very much a different legislative framework going forward in the UK because it just happened to occur at a very precise time when they were doing a review of their health and safety laws as well. And so we've seen that propagate through other countries around the world at the same time, and so that very much informed sort of where the UK went with its safety case legislation that then after Seveso happened in Europe, the Seveso directive then also compounded into that safety case legislation, which was how we get effectively modern safety case legislation around the world now as well.

So Flixborough is one that it really was a turning point for industry because we hadn't focused on processing plants like this in any way before, in any significant way. Hazop had only just been invented by the ICI company. So that had started to be invented into the late-'60s, early-'70s, just before this incident happened, though it wasn't widely published when this incident happened. So we now have structured hazard processes, and all of these things started to happen at around about the same time when Flixborough actually occurred. So it really then did become a catalyst for more rapid and significant change at the time, I think, and it is one of those incidents that, sadly, I'm not sure we're teaching our young engineers enough about it, because you talk to young engineers that's like, "Oh, but that was 50 years ago." Yes, but the lessons are still there. If we still get our management of change wrong, if we still have our people in the wrong place at the wrong time, if we still have people making decisions that they're not capable of making, we can have another one of these incidents happen.

And so we need to always remain vigilant about we can learn and also look at what we can learn coming out of it from safety culture. So safety culture wasn't really a concept back then. We now talk a lot more about organizational culture and how that influences safety and particularly how it influences process safety as well. So I think there's still a lot we can learn either from what we missed at Flixborough or from what we've now seen as a result of Flixborough. This is what we class as one of our true landmark events.

Traci:  Trish, is there anything you want to add on this topic?

Trish: I think for me, one of the most important parts that comes out of it, everybody talks about management of change for Flixborough. Personally, I think one of the most interesting parts for me is actually the capability management and making sure that you've got the right people making the right decisions, and that's a personal hobbyhorse of mine. As a technically qualified mechanical engineer in a world surrounded by a lot of chemical engineers, I find it interesting that even back in the '70s, we were talking about the fact that we needed different disciplines involved.

And so I find that one quite interesting. It's also interesting that as a mechanical engineer in my career, I made mistakes that I should have known better as a mechanical engineer, too, pipeline-related mistakes that I learned a lesson. So even mechanical engineers, like chemical engineers, none of us are perfect, but at least when we come together, we can help each other because we all bring different knowledge to the table, and that for me, I think, is a greater enduring lesson that really is a personal one for me, having been a mechanical engineer in this industry all my life.

Traci: Well, as always, thank you for helping us look back and learn from disasters so that we can become better. Unfortunate events happen all over the world, and we will be here to discuss and learn from them. Subscribe to this free podcast so you can stay on top of best practices. You can also visit us at for more tools and resources aimed at helping you run efficient and safe facilities. On behalf of Trish, I'm Traci, and this is Process Safety with Trish & Traci.

Trish: Stay safe.

About the Author

Traci Purdum | Editor-in-Chief

Traci Purdum, an award-winning business journalist with extensive experience covering manufacturing and management issues, is a graduate of the Kent State University School of Journalism and Mass Communication, Kent, Ohio, and an alumnus of the Wharton Seminar for Business Journalists, Wharton School of Business, University of Pennsylvania, Philadelphia.

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