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Steam Boiler Door

Boiler cement is short-term to get you buy on the assumption that the replacement is imminent (IMHO). Sure it can last a few years. But doing it right means ceramic fiber rope. You use cement and if you fill the keyhole parts of the casting where the sealing rope goes you will be chipping it out or compromising the fit of a proper rope.

I have seen Mills Boilers dating from the 1910 era still working. One I think was earlier than that.

Generally installing a Mills Boiler was a sad event because the installer knew it was his last install in that building... the boiler was expected to outlive him :)


  • David_30
    David_30 Member Posts: 34
    Steam boiler door

    I have an old Mills boiler (circa 1965) and I just noticed that when it is firing I can actually see the flame from the open seam of the plate on which the door to the chamber hangs. Should this be sealed/insulated? The inside of the door has the remnants of what looks like old insulation but there is nothing around the seam of the door or the seam of the plate. Should it be sealed/caulked? Thanks
  • Brad White_36
    Brad White_36 Member Posts: 30
    Unless it is a sight port, you ought not see any flame

    Is it the door itself? Or the plate? Either way see what Smith recommends for ceramic fiber rope, what diameter and so-on. Ideally the combustion chamber should be sealed or you are not really controlling it. And if your chimney gets clogged a bit...

    BTW: "1965" does not denote an "old" Mills Boiler. It is still in it's late teens or early 20's. I would still not trust it with car keys nor alcohol :)
  • David_30
    David_30 Member Posts: 34
    It's the plate...

    It's definitely the plate. Can I simply use some sort of boiler cement around the outside seam of the plate as a short-term fix? Also, should the inside of the door be insulated? I plan to replace the boiler at some point. How long should a Mills last?
  • Guy_6
    Guy_6 Member Posts: 450

    Ah one of mine...
    A mills is considered a lifetime boiler with proper maintenance.

    I will send you the proper Mills parts breakdown so that you can figure out what is needed. Just let me know what model Mills the unit is (250, 350, etc..).

    Guy Woollard
    Smith Boiler Company (MFG of Mills boilers)
  • David_30
    David_30 Member Posts: 34
    Photos attached

    See attached photos. Sadly, it's been converted to gas. Should this thing really last a lifetime? Can you tell exactly how old it is based on this? Any recommendations appreciated. Thanks!
  • adayton_2
    adayton_2 Member Posts: 130
    Weil McLain Door seal

    on our 572 steamer has same condition.So you say perhaps the white ceramic rope-like gasket would be a good seal (far better than none)? Also the mica sighet port is getting holes. Is there a source for mica (2 1/4 inch diameter .010 inch thick) for boiler sight plates? Weil McLain has none and Sid Harvey and Blackman Plumbing have none. Where do you get the ceramic rope gasket?

  • Guy_6
    Guy_6 Member Posts: 450

    My gut says that 3/8 inch rope seal around the inside perimeter of the door , and some insulation board cut to fit the inside should do the trick.
    Let me ask some of the lifers out at Westfield how that particular boiler was sealed, and I will get back to you.

  • David_30
    David_30 Member Posts: 34

    Guy - Sorry to be a pest but have you had any luck determining what size/type ceramic rope seal this would need? Also, any idea how old this boiler really is? Thanks!
  • Yvon Blais
    Yvon Blais Member Posts: 5
    steam boiler door

    Brad ........... it's not a Mills Boiler. It is actually a Smith-Mills Boiler. They had been manufactured by the old HB Smith Foundry in Westfield, MA. They were not manufactured with supply and return headers, such as a true Mills Boiler. Instead, they were dry base, wet leg push nipple type Boilers. Over their design life, they were used for hand fired coal, stoker fired coal, oil fired and gas fired. I even had a pair in a DEM shack in the Pittsfield State Forest area that had a hand fired wood boiler installed in tandem with an oil fired boiler. Both were this same series. Quite the useful apparatus in the "oil crisis" days. The early Boilers, which were designed with a 14" inch dry base eventually lost their base, chambers were eliminated due to the advent of flame retention burners and were re-configured to "base-less" firing, then became known as their "lo-set" design (200L/2000L). Combustion chambers/bases were replaced with steel channels under the boiler. In a lo-set configuration, burners were attached to burner mounting plates (which were replacements for the old-fashioned doors which allowed you to view and tend the coal bed) and you could no longer look at the burner flame. They were dropped by the Foundry sometime in the mid-80s. As to the age of the one I see in the picture, with the insulated metal jacket - it could date back to the early 60's or before. I am not interested in searching through my archives in the attic - it's too cold up there tonight. But, if there is an Insurance Certificate on the wall (typically found in a commercial building) it will give you the installation date.

    Take care Brad

This discussion has been closed.