Animation of 2015 Explosion at ExxonMobil Refinery in Torrance, CA

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Narrator: The Torrance Refinery is a 750 acre facility, located just outside of Los Angeles, California. At the time of the explosion, the refinery was owned by ExxonMobil. An important part of the refining process takes place in the facility's fluid catalytic cracker, or FCC Unit. In the FCC Unit, heavy hydrocarbons from crude oil are broken or cracked into smaller hydrocarbons, which can then be processed into gasoline and other fuel products. The heavy hydrocarbons are first fed into a reactor, where they mix with a catalyst. The heavy liquid hydrocarbons are converted into lighter hydrocarbon vapors, as they travel up the reactor. At the top of the reactor, the lighter hydrocarbon vapors are separated from the catalyst. The hydrocarbon vapors then flow to the main distillation column. The catalyst falls down the side of the reactor, where it moves through a slide valve, to a piece of equipment called the regenerator. During the reaction, a layer of carbon, called "coke" forms on the catalyst, that must be removed. Inside the regenerator, air is added and the coke on the catalyst is burned off. The catalyst is then fed back to the reactor through a slide valve and the cycle is repeated. When the coke is burned off the catalyst, this creates products of combustion called "flue gas". The flue gas flows out the regenerator and enters a system comprised of multiple pieces of equipment, which remove any remaining catalyst particles present. The regenerator and flue gas system comprise the air side of the FCC Unit. The last piece of equipment in the flue gas system is called the "electrostatic precipitator" or ESP. The ESP removes small catalyst particles, using static electricity. While the ESP is energized, it creates sparks, which are sources of ignition. It is critical that the flammable hydrocarbons in the reactor do not flow into the air side of the FCC Unit, as this could create an explosive atmosphere. To avoid this hazard, the two slide valves connecting the reactor and regenerator are used to maintain a catalyst barrier between the pieces of equipment. The sequence of events that eventually led to the explosion at the refinery began on Monday, February 16th, 2015, when a piece of equipment in the air side of the FCC Unit, called the "expander" vibrated forcefully enough that the refinery's control system automatically transitioned the FCC Unit to a standby mode known as "safe park". During safe park mode, the flow of hydrocarbons into the reactor is turned off. The flow of air into the regenerator is also stopped. The two slide valves connecting the reactor and regenerator are closed, to ensure a catalyst barrier is maintained. Steam is then forced into the reactor to prevent hydrocarbons in the main distillation column from flowing back inside. The ESP remains energized during safe park. One slide valve, however, had eroded over six years of operation. And even though it closed, it could not maintain a catalyst barrier in the reactor. Within seven minutes of the Unit going into safe park, all of the catalyst in the reactor fell through the slide valve, into the regenerator. A direct pathway was created for hydrocarbons to flow between the reactor and the regenerator. But the pressure of the steam flowing into the reactor as part of safe park mode was high enough to prevent hydrocarbons in the main column from flowing back inside. With the Unit in safe park mode, operators attempted to restart the expander several times, but were unable to do so. Refinery personnel met to identify a strategy to repair the expander and bring the FCC Unit back online. Operations personnel predicted the expander could not restart, because catalyst had likely accumulated inside. On Tuesday, February 17th, a meeting took place involving a group of refinery personnel. The group discussed a similar expander outage that occurred in 2012, for which the refinery had developed what is called "a variance". A variance is a management approved deviation from procedure. The group decided to use the 2012 variance, which allowed a departure from the typical requirements for isolating the expander. Part of that process involved installing a blind in one of the expander's outlet flanges. On the morning of Wednesday, February 18th, ExxonMobil maintenance attempted to install that blind, but were unable to do so, because steam was escaping through the open flange. Steam from the reactor had traveled through the leaking slide valve, into the air side of the FCC Unit. Using the variance as a guide, the flow of steam into the reactor was decreased in an attempt to reduce the amount escaping from the expander. But the variance did not evaluate whether this flow rate was sufficient to prevent hydrocarbons from flowing into the reactor, from the main distillation column. And unknown to the operators, light hydrocarbons from a separate Unit had flowed through a leaking heat exchanger into the main column, increasing pressure inside. With the steam reduced and less pressure in the reactor, nothing could prevent the hydrocarbons from flowing back from the main distillation column. The hydrocarbons flowed into the reactor, where they escaped through the leaking slide valve, into the air side of the FCC Unit. At 8:07 a.m., a maintenance supervisor, working in the FCC Unit, received an alarm on his personal hydrogen sulfide monitor, warning him that hydrocarbons were leaking nearby. By 8:40 a.m., multiple workers around the expander received the same alarm and the FCC was evacuated. In an attempt to mitigate the problem, a supervisor ordered the flow of steam to the reactor to be increased, but it was too late. A flammable hydrocarbon mixture was flowing through the air side of the FCC Unit and moving toward the ESP, with its multiple ignition sources. There, the flammable hydrocarbon mixture violently exploded. [Sound of explosion]
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Channel: USCSB
Views: 1,412,651
Rating: 4.8506308 out of 5
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Id: JplAKJrgyew
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Length: 7min 12sec (432 seconds)
Published: Wed May 03 2017
Reddit Comments

i'm subscribed to this channel and love to binge it. It scratches that itch that old school history or discovery channel shows did.

πŸ‘οΈŽ︎ 140 πŸ‘€οΈŽ︎ u/RetrogradeMarmalade πŸ“…οΈŽ︎ Jul 26 2018 πŸ—«︎ replies

I could listen to this man describe disasters all day

πŸ‘οΈŽ︎ 77 πŸ‘€οΈŽ︎ u/salmon10 πŸ“…οΈŽ︎ Jul 26 2018 πŸ—«︎ replies

What I don't understand is why the electrostatic precipitator wasn't shut down the second leaking hydrocarbons were detected. Wouldn't it make sense to mitigate the risk of ignition when flammable hydrocarbons are detected in places they shouldn't be?

πŸ‘οΈŽ︎ 54 πŸ‘€οΈŽ︎ u/AllaboutPC πŸ“…οΈŽ︎ Jul 26 2018 πŸ—«︎ replies

By the sounds of it, a lot of equipment failed around the same time. Why wasn't that stuff maintained properly?

πŸ‘οΈŽ︎ 15 πŸ‘€οΈŽ︎ u/nagrom7 πŸ“…οΈŽ︎ Jul 26 2018 πŸ—«︎ replies

The refinery damn near killed thousands thanks to this explosion. A 40 ton chunk of debris crashed three feet away from a tank holding 25 tons of an alkylate called MHF. MHF is both acidic and poisonous. It would've been released as a dense, low-hanging cloud that drifts with the wind... out into population-dense LA. Good luck with that evacuation! A ton of people would've been killed. Hundreds of thousands are still at risk.

Check out https://www.traasouthbay.com/ and (NSFL) https://duckduckgo.com/?q=HF+acid+burns&t=canonical&iax=images&ia=images

πŸ‘οΈŽ︎ 17 πŸ‘€οΈŽ︎ u/plst767 πŸ“…οΈŽ︎ Jul 26 2018 πŸ—«︎ replies

USCSB is both a very cool and highly controversial organization. Some quick hits:

1) The director of the organization recently (I wanna say 2007, plus 10 years) drove the organization into the ground. If you ask people in the industry (Chemical Plants, Chemical Engineers) you'll find that there was not a lot of praise during the Moure-Eraso era of the USCSB, with the main driver being that the quality of the output from the USCSB had fallen in the past years.

Now, you could say that this is because the USCSB took it's model from the NTSB, a very similar organization. The difference is, Cars/Planes etc are all very standard. But each chemical plant is very different. Leading to very long investigations. Overall, the efficacy of the USCSB had been declining for a very long time.

2) Fun fact, Trump's Skinny budget from last year wanted to straight up eliminate the USCSB, despite it being the only chemical safety organization in the US. Keep in mind, every chemical plant has it's own internal process safety boards whose job is to try and prevent these kinds of accidents. But they still happen. The USCSB is a great organization on paper, because they try to determine what went wrong without assigning blame and give suggestions to plants and the industry on how to prevent accidents.

πŸ‘οΈŽ︎ 5 πŸ‘€οΈŽ︎ u/chimpfunkz πŸ“…οΈŽ︎ Jul 26 2018 πŸ—«︎ replies

Oooo now do PEPCON

πŸ‘οΈŽ︎ 12 πŸ‘€οΈŽ︎ u/Oceanswave πŸ“…οΈŽ︎ Jul 26 2018 πŸ—«︎ replies

This is a great find. Thanks for sharing!

πŸ‘οΈŽ︎ 4 πŸ‘€οΈŽ︎ u/spottydodgy πŸ“…οΈŽ︎ Jul 26 2018 πŸ—«︎ replies

Can’t upvote CSB enough

πŸ‘οΈŽ︎ 5 πŸ‘€οΈŽ︎ u/brad274 πŸ“…οΈŽ︎ Jul 26 2018 πŸ—«︎ replies
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