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Gasifier safety issue

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Nofossil, Feb 1, 2008.

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  1. Nofossil

    Nofossil Moderator Emeritus

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    Ran into a frightening situation that's convinced me that there are a couple of steps that would be prudent in any gasifier installation.

    Inexperienced operator was reloading the boiler. A small stick blocked the bypass damper open. Operator closed bypass damper as far as possible and turned on the controller. The 'puff' almost dislodged the stovepipe from the chimney, and blew open the cleanout door at the chimney bottom. Stovepipe temperatures then proceeded to get much higher than normal.

    My thoughts: There needs to be a 'fan disable' relay in series between the controller and the fan so that the fan is disabled unless the relay is energized. The relay power should come through (1) a limit switch that's closed only when the bypass damper is fully closed, and (2) a 'panic' button.

    If you have a fire and can't close (or haven't closed) the bypass damper, then you don't want the fan to run. You might want the controller to be on, though, so that the circ pump can operate.

    If things go wrong, there needs to be a 'panic button' - a clear and appropriate way for a civilian to put the system in a safe condition. My thought is that controller on, fan disabled, and doors closed is the safest state.

    Other thoughts? Do other gasifiers have interlocks or other features to deal with this class of issues?

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  2. Eric Johnson

    Eric Johnson Mod Emeritus

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    How were they able to close the fuel loading door without the bypass damper being fully closed? I thought the handles were designed to prevent that. My point is that if you can't close the door, you know there's a problem with the damper.

    I have a master switch (panic button) that cuts the power to everything but the main circ pump right next to the boiler. Quite often I simply use it and leave the controller switch on.

    Fundamentally, I think most safety features are a good thing, but at the same time, they're one more thing that can go wrong, so I'm not surprised to see them left out of the final product. And Europe, for all its regulations, has some odd attitudes towards safety. Alcohol, for example, is a common thing to find on active logging jobs. Woodcutting safety gear can be hard to find on those same operations, even in the places like Sweden where it supposedly originates.

    But I guess my bottom line is that somebody who doesn't understand the importance and function of the bypass damper probably shouldn't be operating the boiler in the first place.
  3. wdc1160

    wdc1160 New Member

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    2 questions.

    What did the "inexperienced op" do? How did they react to the surprise?

    I have thought about this, and expect idiots to have to operate my boiler while I am away(I can't have you drive to my house to load it afterall). My thoughts centered about the problem of awareness and handling. But, I am stuck/troubled by awareness. How to you indicate a problem to an idiot? (Short of the stovepipe blowing off the damn boiler???)
    I plan on mounting a red led digital display in the shed. This won't go into effect until next year, but I already have the parts. The display will correspond to a course of action or status. I have everthing from water hoses to extinguishers that can be used if I can convince the idiot that there is a problem.

    I have more questions than answers when it comes to idiot proofing. It truely is the hardest endeavor --of this I am sure. GL Bill
  4. Eric Johnson

    Eric Johnson Mod Emeritus

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    Well, Bill, they keep making better idiots, so it's hard to keep up. (Not to suggest that nofossil's inexperienced helper is in any way an idiot).

    I've given this a lot of thought and would have to say that my gasifier is a lot safer, hands down, than any other wood-fired appliance I've every owned. And that's pretty impressive considering that it produces a much hotter flame and puts out a lot more heat than any of the others.

    The lack of creosote and low stack temps alone accomplish that. But beyond the obvious, I have trouble seeing how you could screw up in a way that would do more than fill your house (boiler, room, whatever) with smoke, though I suppose if the stove pipe blew off and the bypass damper was open and the blower was going, you might get some flame shooting out of the chimney connector. But in my case, there's really nothing to burn. And most of the smoke would still get sucked up the chimney.
  5. wdc1160

    wdc1160 New Member

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    Well, are all idiots/rookies at something. Just because you can't load a boiler doesn't mean your doomed to failure in life. Its has become slang term in my consulting without a negative connotation. It derives from idiot proofing software and systems. Ironically not one of the people who would make the mistakes could possibly be considered idiots by any measure. Just a change in the lexicon.

    Keep in mind, I just spent 2 hrs fixing a blown radiator I froze.

    I also have very little that can be burnt, but I don't want to ruin the boiler. I think ruining its most delecate parts in a cold snap could break a great number of pipes.
  6. Eric Johnson

    Eric Johnson Mod Emeritus

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    My understanding is that if you left the ash door and bypass damper open, you could eventually overheat the damper and warp it. But it's easily replaceable. It's just a high-grade steel disk bolted onto a lever. Simply leaving the bypass damper open, even with the blowers going, is not going to overheat the damper flap because there's not enough heat produced in the firebox. And when it gets hot, the blower shuts down. In all likelihood (IMO), the biggest bummer to operating for extended periods with the damper open would be a creosoted chimney.

    I don't see what else could get damaged, short of trying to fire the boiler without any water in it. The low-water cut-off switch provides some protection from that, though you could still ruin it if you really tried.
  7. eekster

    eekster New Member

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    I had a issue last year when using too small of wood and my "puffing" cycle was too long that the bypass damper popped open due to too much smoke in chamber and re- ignition. It never over heated the boiler just burned my wood fast and made alot of smoke out the chimney according to my neighbor. I think that anything that just about could happen last year happened to me. Once again learning the new machine.
    Keith
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