Monday, April 08, 2019

Facts, Investigations, and Rumors: The Houston Tank-Farm Fire

NOTE:  Due to an oversight, this blog was not posted last week.  It was intended to appear on Apr. 1.  My apologies in case you missed it.---KDS

As most readers of this blog know, most of what appears here is commentary on engineering-ethics-related news from other sources.  First-hand reporting is not my bag, if for no other reason that I don't have time for it, and there aren't a lot of sources who are willing to be called at 5 AM, which is usually around the time I'm writing it.  But a week or so ago I received some information almost by chance, and it puts me in something of an ethical dilemma.  Do I write about something that wasn't intended for publication or not?  Well, with certain precautions, I've decided to go ahead.

Here's the known and widely publicized facts:  On Sunday, Mar. 17, a fire began at the Intercontinental Terminals Company (ITC) tank farm in Deer Park, an industrial suburb of Houston.  It quickly spread and at one point involved 11 of the 242 tanks at the facility.  Firefighters could only spread foam on nearby tanks to keep the fire from spreading, but had to wait for the products contained in the tanks to burn away, which took several days.  These products included toluene, xylene, naphtha, and benzene, a known carcinogen.  The fire made a huge black plume visible for miles, and caused the closure of several local school districts for a day or two.  Authorities also temporarily closed a portion of the nearby Houston Channel to shipping due to the fire.

Naturally, the fire is going to be investigated.  Although no one was killed or injured as an immediate result of the fire, millions of dollars' worth of chemicals and plant facilities were destroyed, and an unknown amount of toxic chemicals was released into the air, the ground, and the water nearby.  Anything this consequential is worth investigating because of the lessons that can be learned to avoid similar accidents in the future.

An independent agency, the U. S. Chemical Safety Board, announced last week that it was opening its investigation into the accident.  This board is recognized for its thorough and reliable conduct of mishap investigations, which can take months or even years before a well-researched report is issued.  In the meantime, before such reports are available, the cause remains officially unknown, although the facts that wind up in the official report are presumably somewhere waiting to be investigated.

And in the meantime, the last thing any company official is going to do is talk loosely about what they think might have happened.  This explains the relatively small amount of information that ITC released on its own during the fire, which burned off and on for nearly a week.  Lawyers flock to major accidents like—well, I was going to mention a species of bird, but we'll just let it go at that.  Already the Texas attorney general has announced that he's suing ITC for the pollution caused by the fire, and other suits will follow as night follows the day.  And the less fodder given by a company's officials to lawyers to use against them, the better, as far as the company is concerned.

So much for officialdom.  Now for the rumors and unconfirmed reports.  I did manage to find a reference in a minor Houston news outlet (the Houston Press) to the following report:  "Also Wednesday morning, the Houston Chronicle was quoting an unidentified worker as says the fire may have been started when a tank overheated and a safety valve did not shut that down."  I was unable to locate the original Chronicle story, but (and here's my contribution to the mix), it fits in with what a friend of mine heard from his connections back in Deer Park, where he was raised and worked in the refining business for most of his career before retiring to my area.  For obvious reasons, he will remain anonymous here.

On the Friday after the fire began, he told me the following.  At a tank farm there are tanks, pipes, valves, and pumps to send the various products to nearby facilities or transportation points such as loading locations for tank cars and tank trucks.  Some of these pumps are quite large, using multiple-horsepower motors that consume many kilowatts of power.  If an order comes through to a technician to send a certain amount of product to a certain pipe, the appropriate pump is turned on first and then the valve is opened, because otherwise, unforeseen back pressure or other issues might cause products to go the wrong way and get mixed up.

But it's vitally important, especially when a large powerful pump is involved, to turn on the valve shortly after the pump is turned on.  If this isn't done, all the energy that the pump's spinning impeller puts into the liquid can't go anywhere and turns into heat.  And the product—often a flammable one such as naphtha—can get hot enough to rise past its flash point, so that once the valve is turned on and any air is present, the product will spontaneously catch fire.

Normally there are thermal cutout sensors that will detect when a pump's outlet overheats due to misguided operation such as this, and shut off the pump automatically.  But sensors sometimes fail.

What my friend heard was that someone turned on a pump in preparation for shipping some flammable product out of the plant, but due to paperwork or some other delay, the appropriate valve wasn't turned on for some 17 hours.  That's plenty of time for a pump without a safety thermal cutout to get its product way too hot.  And so sometime Sunday, the product caught fire, and the rest is very public history. 

Distorted through a rumor mill and two news outlets, that more detailed story fits in with the unconfirmed and unattributed report that a "tank overheated" and a "safety valve" (read: thermal cutout) did not shut it down.  So strictly speaking, I'm not reporting a scoop here.  But it does sound like confirmation of another unattributed report.

Whatever the rumors say, we'll have to wait for the Chemical Safety Board to interview everyone concerned, compile the data they can obtain from SCADA (supervisory control and data acquisition) digital records, and anything else they find that's relevant to getting to the bottom of this accident officially.  But in the meantime, plant operators everywhere should pay extra attention to pumps and valves and timing.

Sources:  Besides my friend, I consulted the report on the fire carried by Chemical and Engineering News at and found the unattributed report of the overheated tank at 

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