Boiler explosion caught on nanny cam

Robert O'Connor_12

http://www.liveleak.com/view?i=f36_1426676645

roundrightfarm

what causes this type of explosion?

Paul Pollets

Dry fired HW boiler with defective relief valve and clogged feeder.

Bob Bona_4

Wonder if flooding occurred after.

icesailor

My money goes to a plug in a dripping relief valve.

icesailor

FWIW,

I've seen quite a few dry fired, or little water fired boilers. None of them exploded. They just cracked from overheating.

In the above case, the high limit control should have shut down the boiler before it got too hot. A good reason for a additional high limit control with a manual re-set. Like commercial boilers are supposed to have.

Consider this. A cubic foot of water equals 7 1/2 gallons of water. Water under 12# pressure boils at 244 degrees. That same cubic foot of water at 28# of pressure boils at 296 degrees. The expansion rate as I understand it will cause the cubic water to convert to 1200 cubic feet of steam. If the high limit fails and doesn't shut off the burner, a brand new fill valve operating at 12# PSI isn't going to add water when the system is at 25+ # PSI. The bigger concern is when the relief valve opens when the boiler pressure reaches 30# and starts to relieve. The pressure in the boiler drops, and the entire water content of the boiler converts/expands to steam.

When watching Mythbusters blow up a water heater, It was the drop in pressure below the temperature that causes the explosion. Or the tank rupturing.

Fred

My Dentist told me a couple years ago that his neighbor's boiler exploded and pieces of the cast iron went through the roof and landed in his yard. he lives in an area of very large homes and the boilers are good size but I thought he was exagerating, non the less. Maybe he wasn't!

icesailor

A few weeks ago, someone posted an album of steam boiler explosions. Quite stunning.

RobG

I'd love to find out what the final verdict is of the cause!

icesailor

RobG said:

I'd love to find out what the final verdict is of the cause!

There's a good chance that there will be some element of truth to what happened. You might need a magnifying glass to find it though.

ChrisJ

RobG said:

I'd love to find out what the final verdict is of the cause!

Neglect is my vote.

ChrisJ

icesailor said:

FWIW,

I've seen quite a few dry fired, or little water fired boilers. None of them exploded. They just cracked from overheating.

In the above case, the high limit control should have shut down the boiler before it got too hot. A good reason for a additional high limit control with a manual re-set. Like commercial boilers are supposed to have.

Consider this. A cubic foot of water equals 7 1/2 gallons of water. Water under 12# pressure boils at 244 degrees. That same cubic foot of water at 28# of pressure boils at 296 degrees. The expansion rate as I understand it will cause the cubic water to convert to 1200 cubic feet of steam. If the high limit fails and doesn't shut off the burner, a brand new fill valve operating at 12# PSI isn't going to add water when the system is at 25+ # PSI. The bigger concern is when the relief valve opens when the boiler pressure reaches 30# and starts to relieve. The pressure in the boiler drops, and the entire water content of the boiler converts/expands to steam.

When watching Mythbusters blow up a water heater, It was the drop in pressure below the temperature that causes the explosion. Or the tank rupturing.

What happens when a boiler dry fires because the autofill is clogged and then during it, for some reason the autofill opens?

I'd bet even the pressure relief can't handle that much volume.


EDIT : I just noticed you kind of covered this, but are you 100% sure a broke autofill could not start under those conditions? I have no idea how they work.

EBEBRATT-Ed

water changing to steam expands in volume 1700 times. Visually a box 28" x 28" X 28'' filled with water Change to steam the box would be 28' X 28' x 28' Stuf has some serious getti-up

AlCorelliNY

From the video, the relief valve looks ancient.

Hard to believe that even nowadays, people think gas boilers do not need to be serviced once a year.

What if a child were injured?

ChrisJ

AlCorelliNY said:

From the video, the relief valve looks ancient.

Hard to believe that even nowadays, people think gas boilers do not need to be serviced once a year.

What if a child were injured?

I'd think under those conditions multiple people could have easily been killed.

icesailor

AlCorelliNY said:

From the video, the relief valve looks ancient.

Hard to believe that even nowadays, people think gas boilers do not need to be serviced once a year.

What if a child were injured?

Ancient, and maybe not a 30# relief valve. Like maybe a pressure only valve for potable water. Way higher than 30#. The test lever is broken with a nail through it. It looks like it had been weeping from the rust on the inside of the valve.

I can hear the dialog. "I don't want to call someone to service the boiler. They all try to rip me off. Like the last time, 10 years ago, who told me I needed a new relief valve. Can you imagine? He tried to rip me off."

When the insurance company gets done "Adjusting" for age, They'll give him $100.00 towards a new boiler. What it might have cost to have someone go over the boiler and replace the relief valve.

Safe money says that the boiler was overheating long before the explosion. And Homeowner didn't want to get ripped off by someone. Selling him something he didn't need. He can afford a Nanny for his precious wonder. But can't afford to have his boiler serviced. Like he does all his new cars.

RLuck

I have seen a couple of times when homeowners have put the old style gas valves to manual open and have been very close to this happening. Generally they still have the old style relief that is not attached to the boiler and I doubt works. Wouldn't touch the boiler unless all repairs were made for safety. After hurricain s:andy a home owner did this then flagged down to utility workers walking down the street restoring gas service. As they walked down the basement stairs the boiler let go, leaving them injured and severely burned. (I don't believe the home owner ever admitted what he did, and not much left to prove anything)

AlCorelliNY

Gives a whole new meaning to;
"Back slowly out of the boiler room".

hydro617

I'm going to say faulty relief and hi limit . In turn boiler overheats and relief valve should blowoff. In this case it didn't . So pressure kept building and building until it exceeded max psi rating