I live and own a business a scant few blocks from a large field of petroleum storage tanks near Port Everglades in Fort Lauderdale. My shop is a block from the northern edge of this field of tanks (sounds beautiful, dosen’t it?). A developer is building a new shopping center nearby that is literally right up against the tanks. They’ve managed to convince a lot of the stores in our mall to move over there, but we’ve opted to stay put because we don’t want to be that close to these things.
When I told someone that this was one reason we weren’t moving, he said that was crazy because if the tanks exploded, it wouldn’t matter if you were a block away or right next to them because the explosion would suck out all the oxygen within a six mile area. Knowing almost nothing about science, I put this to the good folks of the Straight Dope board… would the above scenario actually happen in the event of a blast?
No. You would get a big-ass fire, and LOT of heat, but the oxygen sucking thing is just silliness. Just such a tank caught fire in Woodbridge, NJ a few years ago due to a lightning strike and the apparent failure of a safety system. Homes nearby were evacuated, but only because of the heat and smoke.
Also, these tank farms don’t explode or start on fire that easily.
Liquid petroleum doesn’t burn very well, it’s the fumes (petro + air) that is so flammable. In these tank farms, the petrol is kept in large, sealed tanks, not exposed to the air. The operators know very well that it’s the partially empty tank that is dangerous, so they make efforts to avoid that. They try to use from one tank at a time, and they pump petrol back and forth to try to keep tanks either completely full or completely empty.
The operators are well aware of the danger, and are pretty careful to follow proper procedures. (After all, they would be much closer to any explosion or fire than you would be!)
Personally, I’d be more worried about all the tanker trucks that are driving around every day, on roads with lots of careless, nut-case drivers around them.
Like the other two gentlemen have said, these tanks are just not that dangerous. Most heavy oils don’t like to burn to begin with, and don’t burn all that well in a simple open flame condition. There would be no sucking of oxygen to kill people like canaries in a massive coal mine.
The main risk is likely structural failure of the tanks, which can happen, and can lead to a spot flood of #6 oil or whatever soaking several dozen acres.
Our main worry is terrorism. I imagine it would take a awfully large blast to even dent one of those tanks. Authorities had claimed to break up a plot to blow up the large power plant inside the port (also near the tanks), but I don’t think it got past the discussion stage.
I know that a couple of times in Israel, police found remote-controlled explosive devices on the bottom of tankers, and one of them blew up right before the truck was going to load up at one of these farms. If the truck had blown up when it was actually filling it’s tank, the chain-reaction could have killed hundreds.
Back here in Fort Lauderdale, they actually built an apartment development mere feet from one of the tanks (close enough to hit the tank with a rock from your front porch). And the one-bedrooms start at $1300/month! Yeesh!
We worry about that too. Unfortunately, that scenario has happened a few times, usually because the driver is going too fast and wipes out.
It sounded pretty far-fetched, but I figured I’d get a more expert opinion. I imagine these tanks have to be insulated against lightning, since more lightning hits South Florida than anywhere else in the world. I’m sure we deserve it, too.
As for the tank construction, I’m sure Una can give you far more details than I can, but as far as lighting goes, the tanks are pretty well protected simply by being made out of metal. For the most part, they are pretty effective Faraday cages, diverting the electrical current through the metal skin, ultimately to ground. The weak spot is the ventilation, which is present to allow gasses to escape to keep the pressure down. Various safety features are included on and around these vents to prevent ignition due to lightning and static discharge.
Yes…but the good news is that more oxygen would fill in to replace the air used up by the fire. Unless of course you have a six mile dome over your town.
Your friend may have been thinking of the effects of a firestorm. A true firestorm can draw in air from a wide area. I suppose that this could be called “suck[ing] the oxygen” out of the surrounding area, but what your are really talking about is a tornadic effect, with air being drawn into the fire, and that air being replaced from farther away. This makes the fire more intense (think forced-draught furnace), but people are still able to breathe on the outside of the firestorm. Maybe not on the inside, but if you are on the inside of a firestorm, you have bigger problems.
I am no expert on tank farm layout and design, or that of the individual tanks, but I think you’re correct on those points - and the ventillation/fumes aspect is a good point that most don’t consider. Some of these tanks vent through carbon filters and water traps, but there still is a fire risk there.
I work with experts on these things, who are all out today, hopefully not on a 3-day bender. I have never noticed large lightning rods on tanks, and I went through some of my immense power plant digital photo collection and noticed some tanks having small rods, about 1-3 feet in length, which I assume are static discharge rods. I noticed some tanks had large grounding cables running down the side and into the base, presumably to a copper rod, but I don’t know. That’s all I can find…sadly I can’t post any pics from where I am.
