What's a T&P valve for?

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Metal content: A water heater
This site has a downloadable video of an exploding water heater shooting out of a hole in a field. Powered by a deliberately caused boiling water eplosion:
http://www.waterheaterblast.com /
It was only a little 12 gallon job, but the tank landed 400 feet away.
It provides a good graphic demonstration for any fool who wonders why water heaters have to have T&P valves on them and is tempted to replace a dripping T&P valve with a pipe plug.
Imagine what the explosion of a six times larger 80 gallon water heater would have looked like.
Enjoy,
Jeff
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Jeffry Wisnia
(W1BSV + Brass Rat \'57 EE)
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Why would you install your water heater in hole?
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Simon wrote:

Well....Maybe if your home was in a cave?
There once was a hermit named Dave, Who kept a dead whore in his cave. He said, "I'll admit, She smells quite a bit, But look at the money I save!"
Jeff
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Simon wrote:

After watching that - you bet! In a very deep hole - far removed from me!
I wonder if your 'average' terrorist is aware of this?
KNOCK KNOCK!! "yes' HOMELAND SECURITY! "and?" ....WATER HEATER............NO FLY LIST............
Ken.
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Ken Davey wrote:

Fortunately I'm not a terrorist since I though of the hot water as IED idea a long time ago.
Pete C.
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wrote:

I'm surprised that in 14 posts, nobody has yet brought up the explosion vs. BLEVE* distinction. :)
*Boiling Liquid Expanding Vapor Event
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John Husvar wrote:

Plug "ohio steam engine explosion" into Google for info on a October 2001 accident involving a Case 110 steam tractor boiler failure.
Reportedly only operating in the 50 - 70 PSI range.
Old pictures of steam locomatives having 300 PSI boiler failures are impressive. Usually caused by someone not paying attention to the water gauge as I understand it.
Hugh
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No need, thanks. I live nearby. (Akron) :)
Serious accident alright; five killed, many injuries.

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John Husvar wrote:

John Husvar....... or is that John Henry?........ You beat me to it.........
Following courtesy of Peter van der Linden:
You'd better "BLEVE" it Water turning to steam expands 1600 times in volume -- so 2000 gallons of water instantly vaporises to 3 million gallons of steam! It's confined in a metal tube which bursts explosively. The vast majority of boiler explosions are actually firebox failures caused by too little water. These often happen when crossing the summit of a hill. As the grade changes, water surges away from the crown sheet.
See.......... http://afu.com/steam/ ........ for picture..............
A boiler explosion broke this locomotive into small pieces and sprayed them, and the crew, over a wide area of Florida.
The process of hot pressurized water turning into steam can be seen on any car. It's the reason radiators have the warning "don't unscrew this cap while the engine is hot". If you ignore the warning, and unscrew the cap, the pressurized water inside will vaporize and steam up in your face. Casualty departments, police charge sheets, and physics professors refer to this as a BLEVE - Boiling-Liquid Expanding-Vapor Explosion. It also happens when students try to sneak some dry ice out of the lab in a screw-top soda bottle.
Many commercial nuclear reactors are also steam engines. The reactor is the boiler, and it uses nuclear heat to boil water to make steam which drives a turbine that generates electricity. The biggest accident (so far) in history, the 1986 explosion that destroyed reactor 4 at Chernobyl, was a steam BLEVE explosion. It was caused by forcing operation into an unstable area of the power envelope. The engineers were experimenting to see if the turbine self-generated enough power for a safe shutdown, rather than requiring outside power. It turns out that it didn't.
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An exploding pop bottle is just gas pressure. At no point is a pop bottle going to reach over 800PSI inside to liquify CO2.
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Jeff Wisnia wrote:

Exactly. I saw the results of a steam explosion in my neighbor's basement. He rehabbed an old cook stove with a water back but plugged the pipes. Must have been a bit of water still in their. Fortunately, no one was in the basement when it went off and no shrapnel penetrated the overhead.
Harry K

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I'm trying to imagine. For the sake of argument, would it really be any greater. The steam is what causes the heater to explode, right? It seems the heater would explode when a certain pressure was achieved, regardless of the amount of water heated to begin with. Wouldn't the 80 gallons of water tend to hold down the remainder of the heater, thus you might get a greater "flight" from the 12 gallon. I don't believe the entire water contents would "instantly" become steam and rupture the tank. Now, as I said, I'm just trying to imagine what would happen...I don't really know and have no intention of experimenting to find out.
Tom G.
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I don't know either. I wish I had the info, but I saw where a commercial water heater blew. It was a larger one, 125-250 gallons, but I don't remember, but it about destroyed the building it was in and the heater landed several hundred feet out in the parking lot! Greg
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    --FWIW the fact that many of these things seem to blow *up* and land a fair distance from where they started out makes me think the rupture is beginning at the bottom of the pressure vessel. This might mean the thing's filled up with crud and has never been drained properly, thus there is a weak band around the bottom, yes?
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steamer wrote:

The pressure is highest at the bottom.
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I thought pressure was lighter than air and always rose upwards. Which is why airplanes fly and blimps float.
Gunner
The aim of untold millions is to be free to do exactly as they choose and for someone else to pay when things go wrong.
In the past few decades, a peculiar and distinctive psychology has emerged in England. Gone are the civility, sturdy independence, and admirable stoicism that carried the English through the war years . It has been replaced by a constant whine of excuses, complaints, and special pleading. The collapse of the British character has been as swift and complete as the collapse of British power.
Theodore Dalrymple,
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wrote:

At last! A topic I can contribute to on this NG. First, the pressure is higher in the bottom when the contents is all liquid. And yes, it is possible that the crud has corroded a region around or near the bottom. But the real interesting thing is that with a bigger tank you get a bigger explosion. Here's why: The state of a gas is determined by pressure, temperature, quantity of the gas, and the contained volume (remember high school?). For most gasses, if you increase the pressure enough it will liquify. Water, or more precisely water vapor, condenses to a liquid under normal conditions. So the exploding water tank reverses the process. The water is heated throughout so all the water is heated way above the boiling point and most importantly, the pressure is not relieved (it builds up, as a mater of fact). When the tank cracks, even a little, the pressure is suddenly and dramatically reduced within the tank. ALL of the water flashes to steam. Worse, now that the water is a gas it continues to expand and release energy causing more damage (i.e.an explosion). This is why high pressure systems (3000 psi) are tested with liquid and not air. Hope this helps.
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wrote:

pressure is not a "thing" like air or water that can rise or fall.Pressure is a measurement. http://en.wikipedia.org/wiki/Pressure
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On Sun, 16 Jul 2006 11:26:52 -0400, "digitalmaster"

Sigh..I knew I should have added the smilies...but I figured with the blimp comment...
<G>
Gunner
The aim of untold millions is to be free to do exactly as they choose and for someone else to pay when things go wrong.
In the past few decades, a peculiar and distinctive psychology has emerged in England. Gone are the civility, sturdy independence, and admirable stoicism that carried the English through the war years . It has been replaced by a constant whine of excuses, complaints, and special pleading. The collapse of the British character has been as swift and complete as the collapse of British power.
Theodore Dalrymple,
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On Sat, 15 Jul 2006 22:07:08 -0500, "Greg O"

In a closed system without pressure relief, the water can get quite a bit / a lot hotter than 212 without boiling. When the thing does burst, there would be a lot of pressure released from throughout the water, I think.
Something sort of like opening a warm 2-liter bottle of soda after shaking it up

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