What's a T&P valve for?

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

Now, I have learned something. Saw a story on TV the other day about the Mississippi Riverboat explosion at the end of the Civil War that killed about 2500 returning Civil War soldiers and former P.O.Ws. It was supposedly the worst maritime accident ever but we've forgotten it because it's importance was lost to the story of the assassination of President Lincoln. Only a small paragraph or two was reported in the newspapers of the time.

Tom G.

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..........

........ 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.

Sigh..I knew I should have added the smilies...but I figured with the blimp comment...

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,

It would be much greater.

80 gallons of super-heated water (say 400 degrees) turns to much more steam (at 212 degrees) than 12 gallons of water when the pressure is relieved.

Wow! 40 gallons of confined water with 126 degF of superheat has about 44 million joules of energy more than 40 gallons of water at

212F and atmospheric pressure. When the tank blows, that mass of water abruptly reverts to liquid and vapor at 212F and atmospheric pressure by expansion, releasing the 44 megajoules. That's equivalent to about 18 lb of TNT. Doesn't have the brisance of HE, but plenty of boom nonetheless.

Hm. Thinwall pipe containing water and an electric heating element, buried in mole tunnel -- bye, moles! Might also give new context to the term "astro turf"....

Yeah! And it was completely blank out on the TV.

An exploding pop bottle is just gas pressure. At no point is a pop bottle going to reach over 800PSI inside to liquify CO2.

Isn't it wonderful that I live in a place where they don't put all sorts of safety stuff in the lines. If my water heater overheats, the pressure just equalizes with the incoming cold water line since there are no restriction between the water tank to the street water supply.

First the water tank would boil and the pressure would push the water back in the cold water line. When the boiling water level dropped to the upper electrode, the electrode would burn out, possibly turning the power off, but if not, the water would continue to boil until the lower electrode was uncovered which at that time the electrode would burn out and coldwater would fill the tank.

Of course if I had a gas heater (which I do now), it would just boil dry and then the bottom would burn out and cold water would poor in.

I wouldn't notice anything until the water flooded.

I'll bet way more people are killed by lightening each year than by an exploding water tank. Probably about 10,000 to 1 more by lightening.

I've wondered the same thing. You'd have to have a closed valve (or a check valve) before the water heater tank and all the hot water faucets closed to get in trouble. But if it ever did BLEVE, there's a *lot* of energy released.

Bob

Similar to the dynamics of a locomotive boiler going. The initial rupture is of enough violence to releive the pressure on the remainder of the superheated water in the boiler. When it all goes to steam at the same time, it becomes something that one would rather read about than experience. Part of the design of safety valves looks at limiting the rate that pressure is releived for that purpose.

Cheers Trevor Jones

So you could trigger the explosion opening any faucet, hot or cold?

I do not know about check valves but most utility have a antysiphoning valve, should not that vent as the pressure rise above the main?

Not trying to imply the T&P is not necessary, just want to understand all the physic involved.

Mauro

Many municipal water suppliers run over 100 psi, thus requiring each home to have a pressure reducer where the water line enters the home. The pressure reducer would act as a closed valve to a higher downstream pressure.

Shawn

Picture this. Seized up 2 stroke weedeater motor. Piston stuck above the ports. No way to get it out with penetrating oil. Frustration... thinking steam engine. Put a few drops of water in thru the sparkplug hole. Screw in sparkplug. Fire up propane BBQ set to low heat. Place cylinder on grilling surface. Close lid. Go inside house to watch auto racing and drink beer.

5 minutes. nothing. 6 minutes BOOM Piston is shot out of cylinder, thru the lid of cast aluminum grill landing in street about 100 feet away. Neighbors not happy. I still grin about it.

Boilers used to blow all of the time before regulations and Engineering. Purdue University - Boiler Makers

Many a steam engine and train engine and building heating boiler blew... Martin

Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member

D>

You assume electric. Ok - does the stove top or oven element burn out ? It is the same material - cal rod.

Many places have anti-back flow devices at the street so some dufus doesn't set up a sprayer of some agent orange class of material to spray bugs or such - and siphon it into the water system. If the dufus doesn't have his own on the hose line, he will do himself/themselves in.

Which then means another valve in the house must be open to take the expansion.

How about gas ?

Martin Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member

George E. Cawth>

I don't know how many "many" is but I would say that many do not. I say this because heater installation instructions call for a vacuum breaker on the supply line. This prevent tank collapse if water is sucked out the supply line, as when a fire truck is pulling water from a hydrant. In this case water is flowing "backwards" to the street.

My $.02, Bob

-------------------------------- Not likely IMO as the explosion is caused by a sudden rupture of the tank, If the rupture hasn't happened before you open the faucet, opening it only reduces the pressure. Yes, more steam will be released as the pressure drops but the pressure is coming down.

---------------------------------

Any house sytem with a PRV (pressure reducing valve) or on a well system will be a closed system with nowhere for excess pressure to bleed off.

Anti siphoning vavles open when a pressure -drop- occurs. They wouldn't open on a rise in pressure.

Harry K

No need, thanks. I live nearby. (Akron) :)

Serious accident alright; five killed, many injuries.