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Theoretical Boiler Meltdown?

I'm trying to figure out (theoretically) what would happen if the low water cutoff on my boiler failed, all the water boiled out or was lost, and the burner stayed on, for an infinite amount of time (say, if I was away for a weekend).


The melting point of cast iron is 2150F to 2360F according to some random engineering website.  I understand that in the above situation, the boiler would definitely crack, but would the cast iron actually melt?  Would it actually cause a housefire, or would it sit there and fire at an empty cracked boiler until I came home? 


How do you prove this either way, thermodynamicallywise?


Or, better yet, anybody have pics?
beautiful Conshohocken PA


  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    You might wish to ask

    You might wish to ask what would happen if someone were to notice the lack of water, and turn it on. Or if it shut off and water in the system ran back into the boiler.
  • Joe V_2
    Joe V_2 Member Posts: 234
    my guess is

    the burner would fail before meltdown.
  • Matthew Grallert
    Matthew Grallert Member Posts: 109

    This is the result of a run away Smith Pac:-)  I always forget to take before pictures.  The old boiler ran for well over 12 hours before the FD was called.  They shut it down.  LWCO never dropped and the feed never came on.  The boiler cracked, but now melt down.  I think I am going to have to lower those returns. 


  • haaljo
    haaljo Member Posts: 112
    That is a good link. Should have 2 LWCO on all boilers,

    Two automatice water feeders as well and alarms when stuff isn't up to snuff.

    Maybe another $300 if all done at factory. Kind of like air bags.
  • Jamie Hall
    Jamie Hall Member Posts: 22,916
    belt and braces with your pants, sir?

    Not sure what the codes say, but...

    Every boiler should have two LWCOs, one of which is manual reset.  The upper, automatic one can be tied into an automatic water feeder, if you like.  And if you keep track of how much water it feeds.

    Every steam boiler should have at least two pressuretrols.  One of them might be a vapourstat, but the other should be set to something sane -- like 5 psi -- and again be a manual reset.

    And a gauge glass, with blowdown taps.

    And there is no substitute for looking at the dad-burned thing once in a while...

    Just one man's thoughts...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
This discussion has been closed.