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Boiler at Minnesota daycare explodes

There are a few comments that I could make, but I'll let all of you do that.  The pictures are pretty impressive.

<a href="http://www.dli.mn.gov/CCLD/BoilerIncidentsDayCare.asp">http://www.dli.mn.gov/CCLD/BoilerIncidentsDayCare.asp</a>



  • Paul Pollets
    Paul Pollets Member Posts: 3,656

    Looks like a missile strike! Where were the boiler experts that should have been servicing this system? Good thing nobody was hurt.
  • hot_rod
    hot_rod Member Posts: 21,874
    good that nobody was injured

    Had the boiler fill valve been left on... just saying.

    A corroded boiler is safer then an exploding boiler, if it is maintained by un-trained personal regarding LWC operation.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Bob Harper
    Bob Harper Member Posts: 1,030
    root cause?

    From the info. provided, we can make a few assertions:

    -the boiler was improperly installed. You don't valve off a LWCO.

    -when the change in boilers was made, where was the municipal permit and inspection?

    -where is the annual maintenance log by a qualified agency?

    -when was the last time the pressure relief valve was replaced?

    -what was the rating of the PRV?

    -is there a written policy on auto fill valves such as leaving them open?

    -who is there to track fill water consumption and investigate higher than anticipated usage?

    -was the building owner given instructions on the care and maintenance requirements so that they understood how often to call for HVAC service or when?

    -did the HVAC contractor who made the conversions sit down with the owner and review the operation and signs of trouble then draw up a maintenance schedule based upon the individual mfrs. requirements including the LWCO, PRV and fill valves?

    -was a detailed step by step set of written instructions posted in the boiler room clearly visible?

    -was a 24hr. emergency phone number clearly posted in the boiler room?
  • Tom_133
    Tom_133 Member Posts: 880

    I'm sure you figured this out but if you click on the pic in the report a bunch more photos show up!!! That could have been really bad!!
    Montpelier Vt
  • Jamie Hall
    Jamie Hall Member Posts: 22,942
    How many things

    can be done wrong?

    Bob enquires, however, about the rating of the PRV.  It would be interesting to know -- but is irrelevant if the theory that cold water somehow hit the red hot, dry, boiler.  That creates a bomb -- as has been seen -- and no PRV that I know of is going to help.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Bob Harper
    Bob Harper Member Posts: 1,030
    pressure relief

    I agree with you Jamie regarding a PRV being incapable of venting a boiler dry fire. That's why we now require LWCOs on ALL boilers. Yes, when that water expands 1,600 times, a little PRV has no chance of venting it. The most they could hope for would be to control some of the blast in a direction of choice with blast gates and dampers to vent the overpressure.

    I would be curious to know in the days and weeks preceding if the excessive water consumption was not related to a failing PRV or one of a rating too low for the required head pressure while still within that boiler's capability and rating. Same with the autofill valve. Had it ever been serviced or replaced? What was the feed water condition? Prone to causing failures of the components? How about the isolation valve upstream of the fill valve reported to be closed. Was this deliberate, an oversight or did the stem break off leaving the operator to think they left it open?Was the expansion tank waterlogged or diaphragm ruptured?

     Most incidents require a set of conditions, defects, failures or events that collectively result in the Ooops!. Thank God no one hurt.

    I was on another forum and someone pointed out one mfr. clearly stated in their manual to leave the upstream valve 'off'' even when you have an auto fill valve. It really just becomes a pressure reducing fill valve at that point.
  • Jason_13
    Jason_13 Member Posts: 304
    Shut off fill valve

    Not sure if they still do it but B&G stated in their manual for auto-fill valves to close the manual vale prior to the auto-fill when the system is filled and purged.
This discussion has been closed.