Exploding Grill?

[johnmeyer]

I "fixed" a friend's Traeger when it exhibited everything just described except, thankfully, the explosion at the end. The problem is that there is a design flaw. Because of this flaw, sometimes during operation, but mostly at shutdown, the pot fills to the top with pellets before the igniter is turned on.

When the igniter next cycles on when the pot is in this over-full condition, it can heat the chips to where they smoulder, but without enough air being blown through pot to actually ignite the chips into flame. More chips keep coming in from the loader, which continues to smother the ignition. The result? You get fantastic amounts of smoke; unburned chips get pushed up and over the pot edge onto the floor of the smoker, and the darned thing never actually ignites.

The solution is to turn the controller to the full off position, scoop all the semi-burned pellets into a fire-safe container, and then start it up again. It should work fine after that.

I expect the explosion was caused by the dust that gets created as the pellets get partially puverlized in the hopper and loader. If you have too many pellets in the pot, and lots of this dust is mixed in with the pellets, when the blower fan starts up, the dust hits all these glowing pellets and you could easily get the equivalent of the well-known grade school experiment where you create a small explosion using atomized flour.

Check out the following video that shows the power from even a really small amount of dust. All the guy did was load a little bit of flour into a funnel, and put a rubber hose at the end of the funnel so he could blow the flour into tiny little particles. The candle burning in the can provided the ignition.

Spectacular, eh?

 

[RiversideSm0ker]

Offsets don't explode. That's a point in my favor woohoo. I work in IT but sometimes technology scares the crap out of me. Cars that drive themselves into a ditch are another poor example of trying to leap forward a bit too quickly. I like the idea of a pellet grill but if I were to go for a set it and forget it I probably would go with electric. Not that they don't have their own risks but that is just where I imagine I would go.

George

 

[gmc2003]

Am I oversimplifying it or is the solution to always keep the hopper full.

The hopper doesn't have to be full, just keep an eye out for the funnelling of pellets in your hopper, and if the flame goes out then don't try to restart it without cleaning the burnpit out. Restart it like you would do on your initial ignition.

Chris

 

[Javaaman]

The hopper doesn't have to be full, just keep an eye out for the funnelling of pellets in your hopper, and if the flame goes out then don't try to restart it without cleaning the burnpit out. Restart it like you would do on your initial ignition.

Chris

Good advice. Thanks!

 

[hinds90]

Saw this earlier doing some research because I was interested in a pit boss.

 

[johnmeyer]

Saw this earlier doing some research because I was interested in a pit boss.

Yup, that's exactly what I described in my post above, and the explosion looks very much like the flour explosion. Given all the air being pumped into a pellet grill pot, it only takes a very, very small amount of powder to create an explosion like this, if the pellets have pulverized.

Actually, the more I think of it, I don't know why this doesn't happen more often because all the dust from the pellets will tend to go to the bottom of the hopper and therefore when the grill gets into this "flooded" mode, usually at startup, the first thing that will be pumped into the pot will be dust-rich pellets. The smoke, prior to the explosion, is precisely what I saw in my friend's grill while I was troubleshooting it. I now feel very, very lucky to have not been hurt.

To me, this is a fatal flaw (grisly pun intended).

 

[mike243]

I changed pellet flavors fathers day and ran all of the hickory out of the auger tube and when the fire had died out took my air nozzle and blew the dust out of it.Not sure if it will help prevent this or not but easy to do,also the Manuel sez to not shut the lid til a fire is established,I wonder if all of them would do this while starting with the lid closed?

 

[Blue Kettle]

Freaky situation for sure. What's concerning is my Camp Chef is almost continually doing the thing where it funnels out and I'm having to restart the fire on longer Cooks (you can say Keep It full but once you've done to bed...). Guess I I just need to be careful. Definitely makes me wish I'd just bought a 22 inch Smokey mountain and BBQ guru instead.

 

[dward51]

Is it possible that an environment favorable for the "gassification of the wood pellets" occurred? There is a way to extract a burnable gas from wood and bio mass in a low oxygen environment. Wood gas, also called “holzgas”, air gas or blue gas, is the product of thermally gasifying a biomass material. Wood gas is generated in a high temperature chemical reaction (>700°) between the wood and a limited amount of steam or oxygen. The heat and lack of oxygen causes the gases in the wood to release in the form of carbon monoxide, hydrogen and carbon dioxide. The hydrogen will burn (and could also contribute to an explosion in the right conditions). It think this may be the same as the flash over DaveO was referring to.

 

[hinds90]

Yeah after finding these issues over the weekend I'm sticking with my 26 Weber kettle and IQ110.

Freaky situation for sure. What's concerning is my Camp Chef is almost continually doing the thing where it funnels out and I'm having to restart the fire on longer Cooks (you can say Keep It full but once you've done to bed...). Guess I I just need to be careful. Definitely makes me wish I'd just bought a 22 inch Smokey mountain and BBQ guru instead.

 

[bluewhisper]

In structural fires, there is the phenomenon called a "backdraft" where a space like a room is hot enough to burn but it lacks oxygen. Open a door and let air in, and BOOM.