Scary Progress Backpuff

[BKVP]

Thanks for this advice. I was certain I was going to get a backpuff that time - so I raised the draft (in anticipation) from nearly fully shut to about 25% open, and I disengaged the Cat. A couple minutes later was the violent backpuff. I knew it was going to happen but evidently could not prevent it.

I guess the "mistake" was starting out with the air nearly closed when there was so little fuel in the stove. For some reason, when loaded less than half way, it seems more prone to backpuffing. And yes, I do have pretty dry wood, 3 + years stacked and top covered.

The smaller road must be the perfect air to fuel mixture. Try the ssame thing with some 18% moisture content fuel only and see if it still happens.

 

[fire_man]

The smaller road must be the perfect air to fuel mixture. Try the ssame thing with some 18% moisture content fuel only and see if it still happens.

I am definitely going to try this and report back.......

 

[toddnic]

fire_man, I would try to engage the cat at a little higher temp than 250 degrees. I normally engage mine at 350 degrees. Obviously wood gases were accumulating in the firebox that did not have enough oxygen to burn due to the stove being in cat mode with reduced air. When you opened the bypass up and increased the air, the additional wood gas in the firebox now had the ability to combust. Letting the stove get to a higher operating temperature should help alleviate this problem. I've had my PH for 2 years now and have never had one of these issues.

 

[fire_man]

I agree a higher operating temp would help - but what I think that does is simply force a constant flame in the firebox in which case I would never get a backpuff. It only happens when the firebox goes jet black (ie no flames). I have had the stove since 2012 and only had violent backpuffs about 4 times. This one was by far the worst, sounded like someone detonated a bomb. I had no idea wood smoke could ignite so violently. And of course the external spark shower added to the drama.

This explosion was unique for two reasons: 1) I loaded much less wood in the firebox than usual (about 1/3 full). 2) I had disengaged the cat in anticipation of a backpuff, since there was no flame and I knew to expect trouble.

I think BKVP is on to something, I ended up with the perfect air/fuel ratio (lucky me) which would have been prevented with lower MC wood.

Another interesting thought rideau pointed out: Texas Boy has a very similar story. He burned bone dry ancient wood (like 10+ years old) in his Progress and had been operating his bypass accidentally in reverse - he also reported lid popping backpuffs. I am also burning bone dry wood (I figure 4+ years for this load) and had purposely operated the bypass in reverse, thinking it would prevent the backpuff by improving the draft.

 

[Rearscreen]

Isn't this the same phenomenon as grain silo explosions where particles of a flammable particle mixes with the right amount of O2 and all it takes is a spark?