Process Safety New Episode Template

Podcast: Lessons Learned From 1988 Shell Plant Explosion

May 2, 2023
A corroded vapor line caused the deadly incident. This episode talks about ways to stay ahead of corrosion concerns and how to better protect workers in case of unthinkable catastrophe.


Welcome to Process Safety with Trish and Traci, the podcast that aims to share insights from past incidents to help avoid future events. This podcast and its transcript can be found at I'm Traci, editor-in-chief of Chemical Processing and as always, I'm joined by Trish Kerin, the director of the IChemE Safety Centre. Hey Trish, how are you?

Trish: Hey, Traci. I'm doing well today. How are you doing?

Traci: I'm doing wonderfully well and I did want to take this opportunity to congratulate you on winning a bronze ASBE for your 2022 article, Take the Right Steps with Hazard Assessments. That was our cover story for the October issue last year and the American Society of Business Publication editors were ASBE, as we call it, has awarded Chemical Processing three regional editorial awards, including yours in their 2023 ASBE Awards for Excellence Competition. The Annual ASBE Awards honor the best in B2B media, recognizing outstanding work by B2B Trade Publications, association and professional publications, and it's one of the most competitive awards programs for trade media, so that's a pretty big honor for you. Kudos to you on that.

Trish: Thanks. It is a bit of a surprise as an engineer that typically is not always the best at communication as a stereotype of engineers to get an award like that.

Traci: Well, and more kudos to you. We just had our editorial board meeting yesterday and our board members were really over the moon with your Stay Safe column and they were pleased with the zoology lesson they learned from the Platypus column and the Shell Middens column, so congratulations on that as well for launching a great Stay Safe column for us in chemical processing.

Trish: Thank you. I really enjoy writing those ones that it is a great chance for me to get a little bit creative out there.

Traci: And we did launch our first In Case You Missed It episode with you reading your first column for us. So one of our internal editors said, "Oh, it's Chemical Processing in a pleasant voice. It's like story time with Chemical Processing."

Trish: I did once get told I had a voice for radio.

Traci: Well, it is a very soothing voice. All right, well let's get onto the serious portion of this. In today's episode, we are going to look back on the 1988 Shell Plant explosion in Norco, Louisiana. An early morning explosion from the plant killed seven Shell workers, destroyed homes in the community and released 159 million pounds of chemical waste into the atmosphere. Can you give us a little bit of insight into what happened 35 years ago?

Trish: Yeah, so this was a very tragic event that took place. Within the catalytic cracking unit there was a vapor line coming off the overhead of a depropanizer and that line was at reasonable pressure from 1900 KPI or 270 pound at the time. It's believed that it had a catastrophic failure on that eight-inch line... Sorry, 10-inch line and it released a substantial amount of gas that found an ignition source. And the fact is that when we do release substantial amounts of gas, they will typically at some point find an ignition source. And what ended up occurring was a massive explosion that killed seven workers at the time that it occurred. One of the interesting parts as you mentioned, is that with those workers, they were in various locations around the plant when that explosion happened, but five of them were actually in the control room and we'll talk a little bit more about that in a moment. But it's believed that the line failed catastrophically due to corrosion and corrosion is always one of these things that we need to be very careful about managing.

It exists all around us and it will happen whether we are paying attention to it or not. So the catch is, we have to pay attention to what's happening with corrosion. We have to focus on it, we have to understand the mechanisms because if we don't, we can see catastrophic events like this happen. I mean, there was debris found up to five miles away from the site of the explosion when that occurred. It said that it was heard in New Orleans, which was 25 miles away and apparently even set off some burglar alarms in New Orleans with the shockwave. So this was a very substantial explosion that happened.

Traci: In just reading about that, just it's amazing that the distance that in 25 miles away in New Orleans to hear that explosion. I can't imagine what it was like at ground zero there. And you had mentioned, obviously, the corrosion. Corrosion is a concern for facilities and the culprit for many incidents including this one. How best to get ahead of that? Is there constant testing to be done? Is it a maintenance issue? Is it an operational issue? Is it a management issue?

Trish: It's all of them. From a management perspective, we need to make sure that we have robust corrosion management plans in place. That means we need to understand the chemical conditions that are within the equipment and manage within those. So whether that is understanding what impact chlorine potentially has in your system because chlorine can cause stress corrosion cracking, hydrogen can cause stress corrosion cracking, and that's a different form of corrosion to iron oxidation that we see that occurs. So your standard... When we think of corrosion, most people just think of rust and rust happens and that's what corrosion is. Corrosion's actually far more complicated than that. It's a chemical reaction going on between the product in the vessel and the vessel itself. And so you clearly need to understand the chemistry of what's going on there and what can change that chemistry. A change in the temperature of operation, a change in the ambient temperature, a change in the humidity in the environment can have all sorts of impacts on corrosion.

So we can have another one called corrosion under insulation, which is also very common. That's where if we get moisture within the insulation of insulated pipes, then it creates an amazing little environment for corrosion to occur. So we need to understand the chemistry and then we need to make sure that we have adequate risk-based monitoring of the equipment. So that means we need to go out and inspect it and look at it, whether that's physically looking at the outside under things like corrosion, under insulation, that's actually what needs to happen. You actually need to take some insulation off and take a look at the equipment. Whether it is underground corrosion, whether it is internal corrosion, we might need to do ultrasonic testing, thickness testing of the pipework and science can direct us in all sorts of different areas of the key areas where we're likely to see corrosion and that's where you need to focus your testing on.

There have been many incidents have occurred because there have been corrosion management processes, but they haven't been focused in the right areas. They weren't looking at the areas where corrosion happens. They were looking at other areas and we understand, in theory, where corrosion happens. If it is your standard corrosion related to iron oxidation, then typically it's going to occur at the six o'clock point of a pipe. That's quite common. It's going to occur at elbows, it's going to occur near the welds on pipes. We know where these things are going to happen. We can look for them. If we understand the chemistry of what's going on, we can look for it. So we need to know the chemistry. We need to actively manage it and look for it and maintain for it, and we need to have replacement and repair programs in place so that when we find something, we actually fix it, not just wait and see how bad it gets or let it go to failure, particularly if it's holding a hydrocarbon or a flammable substance in it. We cannot run those things to failure.

So, there's some of the sorts of things that we need to do. Now if you are the operator in a facility, you need to be keeping your eyes open. You need to be looking, you need to be making note of unusual things that might be happening. If you're the maintenance people the same. You need to not only be managing the maintenance system and those activities in terms of preventative and predictive maintenance, but you also need to be keeping your eyes open and looking at what's going on. And then if you're the management, as I said, you need to make sure this process works. You need to make sure it's adequately funded. You need to make sure that you've got the right resources looking in the right places for this corrosion. Otherwise, it will happen because this is a chemical reaction that occurs and there's nothing we can typically do to stop the reaction. What we can do is manage its impact. In some rare instances, we can inhibit corrosion, we can stop the reactions occurring, but mostly in our product lines we can't. It's going to happen. We need to manage it.

Traci: You mentioned that the corrosion will happen and you know it's going to happen in certain areas, the welds and the elbows and the six o'clock. So if it happens in one area, is it safe to say that it's happened all throughout and do you have to deal with everything or do you just fix that one area?

Trish: I think you have to be willing to look and explore what's going on in the other areas because if you've got the right environmental conditions and I mean environmental both inside and outside of the vessel going on, then the chemistry says there's going to be corrosion occurring, the reaction is going to be taking place. You have to look for it and that's why you typically have quite substantial corrosion management programs where you will take sections at a time and you do risk assessments to decide which sections you look at first. You've got to make sure you've got quality data going into those risk assessments, so you're looking in the right places at the right priority and then understand that if you do find corrosion somewhere, you've got to expect it's going to be elsewhere. It's rare that corrosion ever just occurs in one place only and never anywhere else. In fact, I'm not aware of that ever happening. So it's going to be somewhere else. You've got to look and find it.

Traci: You talked about the five workers that were found fatally injured inside the catalytic cracking unit control room as a direct result of this blast. What can we learn from that?

Trish: So here's where we start to talk about occupied buildings and making sure that we have people away from the risk areas. The first significant incident example that we talk about when we talk about occupied buildings is actually Flixborough in the United Kingdom, and that's actually having its 50th anniversary next year. Next year we'll be remembering 50 years since Flixborough and that was a significant incident that completely destroyed the control room. In this incident, as well, we're looking at a control room that was basically destroyed and the people inside it didn't survive when the blast happened. We used to build plants with control rooms right in the middle of the plant so that the operators didn't have to walk too far to get to the plant and they were right in there, in the heat of it. They knew what was going on, they were involved in the whole process.

But when an incident happens, if you've still got a control room that's right in the middle and you haven't done anything to strengthen it, that is basically an area where, if an explosion happens and people are in there, they're going to die in there. So we really need to be careful about making sure we manage our occupied buildings very well, whether that's either moving the buildings elsewhere so that the operators, you don't have a large gathering of people in the area where an explosion could occur or it is armoring those buildings in a way that protects the inhabitants. And there's a range of ways to do that as well. You don't need to actually build a blast-proof building that's going to survive, potentially. You might only need to armor it so that it survives enough to protect the people inside. Then the buildings are knocked down because in an explosion event, you've got a lot of damage occurring in a lot of places.

It's not going to be only worrying about having to knock down that building. You're going to be knocking down a lot of other things to bring the facility back online. Making sure we understand that and again, in 2005 we got another big wakeup call on occupied buildings with the Texas City refinery incident, and that was the demountable trailer in the Raff eight unit. So we saw the people killed within that demountable trailer during that tragic start-up incident. I think of the 15 that were killed in that incident, 11 of them were in the trailer, from memory. When we have people inside buildings in areas where we can have the blast radius occur, we need to be concerned about how we're managing the safety of those people in an incident. We need to understand the occupied building risk we've got and we need to take controls to address that occupied building risk.

Now, when we think about that occupied building as well, you'll often in your risk assessments say, "Okay, so we need to think about how often people are there and we can rationalize a way that it's not really that big a risk because they might not be there all the time." It's not occupied all the time. But you also need to take into account that when an incident occurs or an incident's starting to evolve, you may have a situation where people are drawn to it to respond. Be really careful about whether you're trying to justify a way doing improvement work to a control building for occupied reasons. If you are justifying not doing it based on, "We don't have people there," because in an incident, as an incident unfolds, you will have people there, and so your occupancy numbers are higher than you think they are.

You need to be very careful about falling into that trap as well. So we need to make sure that we really learn this lesson of occupied buildings because so many people have tragically died in buildings as a result of explosions. We need to learn this lesson. We can't keep doing it.

Traci: Are most occupied buildings reinforced properly or is that an exception to the rule? Are there only a few buildings that do it right? I'm trying to understand if we do get it right more than we don't or if there's a bigger problem.

Trish: Look, I think we get it right in newer facilities, without doubt. What worries me is there's some small facilities around the world all over the place that still have old original control buildings in them, and these facilities have not seen any significant financial investment in upgrading them at all, across the entire facility, and they're still running. We have an enormous legacy issue here because we didn't always get it right when we built it, and we haven't necessarily fixed those issues. I couldn't tell you how many we have relative to how many are good, and I'm sure that there are a lot of companies out there investing a lot of money in getting it right. And there are companies that can provide you with demountable shipping container-type reinforced buildings for various points in time or for even putting control rooms in at that point in time.

When I see new facilities, I'm seeing a lot of explosion proof buildings, which is fantastic. But when I see old facilities, I'm still seeing the buildings are still there and they're tucked away and you get the, "Oh, we don't use them very much at all." So okay, but at night shift, when the operator is there in the middle of the night, are they in that building rather than in the nice new building you built them because it's 500 meters away? Where are people actually spending their time? Do we really know? When we still leave these buildings in place are people actually still using them? That is a possibility. And likewise, as I said, a number of facilities that have probably never invested in it because it's one of those, "Well, that's never going to happen here anyway." Sadly, I'm sure all these facilities thought it was never going to happen there, and it did and it killed people.

Traci: You've mentioned before that that's a very wrong statement, a dangerous statement, "It can never happen here." Here we are 35 years later and there are still reports of residents suffering from illnesses borne from this incident. What insight can be applied to avoid this impact to the communities in the future?

Trish: Well, fundamentally, the best way to avoid the impact is to have systems in place to manage your corrosion. Then you make sure that you have processes in place that if you do have a leak that it's detected and it's dealt with. So things like water fog automatically activated on gas detection to knock down the vapor cloud so the ignition doesn't happen. And I've seen some really interesting developments in recent years around ways that those sort of things, either foam or water fog can be deployed or even a dry powder can be deployed to knock down a vapor cloud before it finds an ignition source. Some amazing technology coming out there. So there's a whole lot of interesting ways to prevent the incident happening. Fundamentally manage your corrosion and you won't have a corrosion-related loss of containment. So if you get that bit right, then we're not impacting the community at all, and that's something that we need to be focusing on.

Then in the instance, if it does occur, preventing that ignition source in any ways that we can, knocking down the vapor cloud. Then lastly, making sure we have good communication protocols with our neighbors so that we can inform them of whether they need to shelter in place and what that actually means for them, or whether they need to evacuate and get them out of there before they suffer illness related to exposure to whatever is in the air at the time. So we really need to make sure that it's a multipronged attack here, but let's remember and focus on if we don't have the explosion in the first place, the community's not impacted. Let's get the preventative bit right so we don't have the incident. There's so many benefits to not having the incident. Then if it does happen, how do we mitigate it? We've got to get better at that mitigation stuff. As I said, there's a lot of new technologies out there now to prevent vapor clouds exploding, which is amazing stuff. Then making sure that we have the emergency response as well. Those three stages need to all be dealt with adequately.

Traci: Anything you'd like to add that we haven't touched on?

Trish: Oh, I remember years ago sitting in my office when I worked in a refinery, and at the time I was a very young engineer and I don't think I knew any better and I sat in my office and I had a lovely big window, and that window overlooked the reformers very close. And I think back now, and I'm horrified that I used to sit there every day looking at these reformers and during startup and shut down for maintenance activities there was a little car park just outside my window between the reformers and my office, and that used to be the contractor lay down area and there would be demountable huts in there for the contractors when we did the turnarounds. I hope we've learned, I hope we've got better because time and time again we've seen that that is not a safe thing to do.

Years ago I got to revisit the refinery I worked at and I actually went back to the building I used to work in. I went back to my old office and it still overlooks the reformers, but remember how I said there are ways to armor a building? The building won't necessarily survive, but the inhabitants of the building will? That refinery had done that. They had basically, they build an exoskeleton, so to speak, on the outside of the building so that it bears the brunt of the explosion. Now the buildings are knocked down afterwards, but the people inside survive it. It stops the blast wave smashing glass through the buildings. It stops the blast wave entering the building effectively. And I looked at that and I thought, "Oh wow, that's actually impressive. I wish that we had of had that when I was here." But then as I said, at the time, I was a young naive engineer and I don't think I really realized the risk of what I was looking at at the time.

But there are ways that we can improve even the older sites. So take a look at what you can do. If you've got people in buildings that are located within a credible blast zone in your facility, you got to do something about it.

Traci: Well, Trish, thank you for the thoughtful insight. Always appreciate when you pull your past into it and put us in your shoes, and I think that really resonates well. 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 and 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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