We heard a LOUD bang !

Christian Egli_2

First off, rushing to the defense of steam that just does not go around blowing up things: it takes frying pan searing hot heat to build a 100 PSI head. You would be grilling a steak on top of the tank. Something else should happen before we reach the medium rare point. Neither is 100 PSI all that much pressure, but your tank has to be built strong.

In that regards, this tank has a very large diameter, which is good for volume, but terrible for strength. Because of the double increased diameter, the cylindrical tank walls need to be doubly thick compared to a more slender pressure vessel. The sheet metal in this tank does not seem all that thick (but I can't tell from the pictures and we'd have to do some math) and so, this could indicate a weak design that stretched safety factors a bit too thin. Given a choice, a slender tank is a potentially much stronger design -hoping of course the metal thickness is not paper thin either.

That said however, there are forces of nature we can't do anything about. Even if this tank had been built like a double vault Fort Knox type safe it would still blow up when faced with 1) unprovided-for thermal expansion of its water content, and 2) the ram effect of water hammer. That's why expansion tanks are needed, and it is important they are sized correctly and that they don't become water logged.

Back to some conspiracy theories.

This failure happened right at the weld. The weld failed. Welds are a weak point, they often are because of faulty welding. Several things can go wrong.

Primo

Perhaps in an attempt to make the tank strong with still the same thin thickness, rather than using a thick layer of low carbon mild steel which is nice and soft, they went for a significantly stronger steel which contains more carbon. Nothing terribly wrong except that successful welds are that much more difficult to produce on carbon containing steel, incrementally so. Past about 0.3% carbon content (30 points as in 1030 steel), you're on your own trying to keep your welds from cracking. Ever noticed the Do Not Weld labels on truck chassis frames?

It's because of the heat treating abilities steel starts acquiring beyond the 0.3%. You now can harden the stuff by heating it red hot -which happens during arc welding- and it becomes hard and brittle. Brittle things crack and break, and that's life. There are ways to deal with this unwanted hardening, but they are way beyond the scope of the ordinary.

Secundo

Hydrogen.... hydROgen... hYdrogen... Oooh... This gas of the future is found in the most common of all places: within water molecules. And if you weld with coated welding rods that contain moisture from the air (which is hard to avoid) this moisture will be avidly absorbed by the molten metal in the mini furnace you've created within the electric arc. This moisture becomes dissociated hydrogen which, included within the metal, makes the steel terribly brittle. Oh dear.

Now, I dont' suspect an atmosphere controlled welding assembly line would use wet welding rods, nevertheless these two problems I just described are very common and they are largely misunderstood or ignored by most. Oh well.

And now, for a little sales pitch

Consider steam is a gas; like air, it complies easily with what we want to do because it is bendable and compressible. This is a very nice feature of gasses. Oppositely, liquids are stubbornly incompressible. Such is water. If you mess with it, it strikes you with a flood. Like my flood of words here...

I hope this was fun, because learning is always fun. Thanks for the sobering pictures. It was a bang.

ScottMP

Good customers where sitting down

for dinner when they heard a loud BANG. They went into the basement and thier Amtrol indirect was spewing hot water. I shut it off and said we would be back in the morning to replace it. I told them that when the bladder fails the Steel jacket rusts away and the get a hole in them about the size of a pencil ( my experience ).

They told me this was a pretty big bang. Since they had it covered with an insulation blanket I could'nt see the hole.

Every ask a customer what they have for a Water Heater and they describe the Amtrol as the big blue bomb like thing ? I guess there's a reason ......

Check out the photo of what we found when we took off the insulation. Scary !!

Scott


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Bill Nye_2

Yeah but

But Scott, that must only happen with the wood fired ones. I see the pile of firewood to right of your photo.

Did that happen due to natural causes ? Or was there a runaway limit or jumped out aquastat ? or flash to steam or any other weird occurence?

Guy_6

Wow

I would say that a flash to steam would be fairly unlikely in an indirect, but it would appear that they could use an expansion tank on the DHW side.

[Deleted User]

Wow...

I wonder what the actual vessel looks like?

I'd bet a box of donuts that the maker would like to see the installation and the tank...

ME

Brad White_9

Big Bang Theory...

Explosion- water was evident so hydrogen was involved... looks like a hydrogen bomb... works for me!

You can see at least one main point of failure right on the rolled seam, but what is the hole at 11:00 O'Clock?

I agree that knowing the pressure is a good thing and that a potable X-Tank might have postponed this, probably not prevented it. How old is the tank?

ScottMP

I have seen

Amtrol tanks bladder fail and then the insulation soaks up the water and eventually rusts away the steel tank.

Could steam have built up in the liner between the steel tank and bladder ?

Scott

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ScottMP

Bill

That photo os back at out shop. No jumped out limit.

As far as I can see its wear and tear.

We will check for other problems.

Scott

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Cosmo_3

what temp?

Scott,

What temp was the indirect set for? I can't see how the jacket could have gotten hot enough... Was the indirect thermostat pegged on, or the thermocouple temp sensor not working? What temperature is the boiler hi limit set for? Did this tank have a vacuum breaker installed?

Scary sight, I've installed lots of em over the years......


Cosmo

Cosmo_3

oh yeah

I was on a service call about 7 years ago on a leaking Amtrol indirect. When I saw the installation I noted that the 7" exhaust vent off the boiler was touching the water heater. I wondered if this heat might have weakened the inner plastic tank when the boiler was running and caused the leak.

I never got the chance to cut the tank and see because the homeowner wanted to keep the tank to fight over the replacement cost with the original installer, who wouldn't come out on the water leak call. Boy that job was a mess, especially having to be a witness when the homeowner sued the original installer......


Cosmo

hr

I had one do the same thing

but it separated around the belly weld seam. Used to be the bladder would develop a leak where the top nipple came through the tank.

Water would get between the bladder and the steel tank and rust away at that weld seam.

Same loud bang you described, and the whole top lifted several inches from the bottom half!

I think it was Ed N over at Viessmann, a former Amtrol guy that explained the "weak link" with these closet bombs

hot rod

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Gene_3

If they had covered it with insulation

they created the problem, possibly, the heat may cause a problem, they are not...actually no w/h except for electric should ever be insulated.

I used to work at a co. that rented w/h's and we a hell of time with customers that would insulate our oil fired and indirect water heaters, most burned out, you'd think that an indirect would not have a problem but they do, I wish I could find my old literature on it but can't, anyone got more info??

I did a search on the net --amtrol boilermate insulated fails splits explodes-- and got no hits

I'd call Amtrol and see what they say.

John Ruhnke

Steam....

I think I know what happened.

Water boils at 212 and 0 lbs pressure. The water in the tank on the pressure side of the liner was most likely over 210 or close to it. On the other side of the bladder the pressure was less, maybe even in a vacuum. This caused the water to boil. Water turned to steam. Pressure built up between the jacket and the bladder. Then..........

KaBoom!!

JR

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ScottMP

Too Much Insulation ?

I don't know on an indirect ? Viessmann has three inches, seems to work fine.

Scott

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ScottMP

John

I'll ask if the owners had experienced any high water temperatures but you would have thought I would have got a call Long before this happened. These people are friends and live right around the corner from me. Not like them not to mention it.

Then again it could have had a run away limit that night>


Scott

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Brad White_9

Das Hindenburg

Wild postulation here... I was partly serious about the hydrogen aspect, normal in electric water heaters. Wondering if some hydrogen built up and ignited. I do not see the steam theory holding water (so to speak), nor the vacuum assist. Compressible rather than ignitable gasses compared to water and all. If not an ignition of flammable gas, I would focus on the incompressible fluid theory. I could easily be wrong, but have my hunches.

What is the condition of the metal at the seam? Is it thinner than the rest? (That is metal is it not? The plastic liners I have seen are waxy-white color.)

Would be interesting to find out.

John Ruhnke

No carbon build up...........

Brad,

I don't see any signs of carbon or heat build up as in a high temp explosion such as could be caused by hydrogen though. The edges look clean. They aren't discolored either. Leads me to believe my steam theory. Interesting hydrogen theory though. I could be wrong too. I am just guessing.

JR

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Brad White_9

Hydrogen

does not need carbon to ignite (except for the proverbial match stick! ) Any carbonization occurs as collateral damage and secondary combustion. (Fuel cells as one specific aspect use pure O2 or air devoid of CO2.)

In conventional ignition the only carbon generally present is that within the atmosphere as CO2, not enough to soot anything.

Cosmo_3

hydrogen

Brad may have a good point. I have seen evidence of a hydrogen explosion in a dishwasher. One of the guys brought an article to the Master Plumber's Meeting.

Seems the gas collected in the hot water heater, and the homeowner had been away on vacation for 6 months. Upon her return the first thing she did was throw some dusty dishes in the dishwasher, and kaboom.

Found a link- http://www.amresupply.com/industrynews.php?viewupdate=indupd828122&PHPSESSID=a404a25293a57d929a7bad24312ddbf7

But where did the spark come from in an indirect water heater?

Cosmo

Al Corelli

We've replace dozens

We've replaced dozens of these, possibly hundreds over the years.

As described above, the plastic tank fails and water leaks out into the insulation where it starts rust that kills the outer tank shell.

Troy_3

Amtrol

I have seen this also. I make it a point to touch these whenever I go near them. If they are warm to the touch the end is near. Let me save you the call- It's not their fault. I was credited $80 for my last dead amtrol. Whuppee!

Plumdog_2

Two Times

I had those fail because of leak between the bladder and the nipples. Niether popped open but I had to eat the labor costs for replacement twice. No more Amtrol tanks for me. The engineer at the factory told me every one of them is defective.

Leo

If this is

If this the tank I think it is, look underneath at the little relay and see if it is hanging up causing the circulator to stay on and overheat.

Leo

Scott Gregg

Never seen it

I've never seen it happen to a Bock! Loks like a pressure issue with the blown out rupture, but it might be time to put in something better.

Unknown

amtrol tank

I don't have any experinces with the indirect tanks as I the part of counrty are free standing water heaters.. However, as a well water contractor, I will never use amtrol tanks due to tank fittings failing at bottom as well plugging at the elbow... I found out they went cheapie by using the black iron elbow and painted blue... We all know not to use black fittings on plumbing... I still have the elbow in my garage for the stake of arguement from the last victim, my home. Now I'm seeing extrol tanks failing in short time...
Any helps from Amtrol... Don't count on it.

Bill Nye_2

amtrol

Hey they try. The well-x-trol tanks have a SS elbow now. I replaced an 11 yr old tank with the plugged elbow just yesterday.

I have replaced too many leaking hot water makers. Never saw one blow up though.

When ever there were issues they stepped up with improvements. Like CU/Ni coils etc. I think they have one with the coil on top now.

Water conditions, enviroment, usage, etc. play a big part in how long a product will last. Water + metal = rust fe + H2O = oxidation reduction

Weezbo

BANG! is not good. Trust me on this one*~/:)

The cold does some severe stuff to anything man made:) that tanks looks old enough to have been made in another century ....maybe its the light...does it have a product date on it?

Gene_3

ok let me ask this

it looks like that tank split above the weld on the fold, not right on the weld and it split up the side where no seam existed, now that rot spot to the left near the top of the tear, is that where it was leaking?

if so is all the metal rotted beneath from there down??

I'm wondering if that was rotted and then with a water hammer the tank split?? but it sure looks like a violent split that I can't explain with just rot, I could see it rotting and leaking but the split is akin to a super heated condition, if I'm looking at the picture right, that seems to not be explainable.

Has anyone else seen one go EXACTLY LIKE THIS??

I was thinking about putting a new Amtrol top down with 2 coils so I could hook up to solar panels, maybe I should rethink??

much appreciated in advance