So the other day I wet down the coal around the perimeter of my fire to keep it’s size contained and the second I started to crank my blower there was a deafening explosion/backfire in the three foot or so tin pipe connecting my blower and forge. Apparently the addition of water and the resulting steam pressure forced coal gas down into the air supply pipe and as soon as I started to push it up into the fire it ignited. Needless to say—it startled the XXXXX out of me!
Has anyone else had this experience?

I know that it can be a problem in coal stoves.

It can be a worthwhile investment of time to spend a day with an experienced smith focusing on coal fire management. I realize this may sound excessive, but there are nuances of coal fire management that are extremely difficult to learn from the exchange of Internet conversations. .... that said, try poking a hole in the center of your fire prior to containing the fire with water around the edges.

I have heard stories of bellows exploding from filling up with coal gas. It is best to open your ash gate or close the air gate if the fire will be unattended for any length of time.

I have personally experienced backfires and they WILL get your attention.

Many old time smiths know their forge and will first give a small and very gentle amount of air before going full throttle.

Keep the blower turning a little when your wetting the coal.

Yes. Keep the air moving when you add that water. You will experience little problems.

the fire is just reminding you you're alive! :o and to change your pants! :blink:

Right! I blew the counterwieght clean-off this bellows. I have had a number of backfires, but none while I had visitors here, thank the Lord!

By the way, I was trained on this forge, which I operate for the society and waas told that the explosion(s) I have is generated by the steam when too much water is applied and too quickly applied. The air blast really helps out, but if you stop the air too soon, it will still backfire, although not quite as strong.

I have never opened the ash dump when I leave the fire for hours at a time. To my knowledge I haven't had a "gas" eplosion when I'm not there. Then again, if a tree falls in the woods and nobody hears it, does it make a noise??????

we get them at Tannehill every once in a while..... we just tell our students that it is the past resident blacksmith Bill Shoemaker playing practical jokes on us from beyond the grave... It happens at our forges when the wind blows over the top of the forge for anytime pushing the gasses up the pipe going to the blower... it normally happens while we are letting our forges "coke up" a little. and yes, you may need to change your pants after it goes off like a shotgun

passing steam over hot coke was the method they used to get gas for all the gas lights of victorian times; and the old "committing suicide by sticking your head in the oven" as CO was a major part of it back before natural gas took over.

Experience with your system helps as does having a "weak link" so you don't blow up your bellows but rather pop a lightly fit connection that's easily put back together.

I've had it happen. The ash dump seems to serve as a pressure relief valve. But yeah, it gets your attention. :)

When I used dirty coal from an old tram bridge I learned to leave the ash dump opened when forging. When returning to the fire I twisted the blower to blow out the carbide gas and then closed the ash dump.

Do any of you old timers remember the little carbide cannons that were sold in toy stores and hardware stores?

Not carbide gas. Carbide gas is Acetylene. I've spent many an hour caving with a carbide lantern on my hard hat when I was younger. Still have a can on the shelf.

You are correct about carbide gas being acetylene. It is explosive when ignited in a confined space; bright when ignited in the open.

I got to experience backfiring on Sunday with my little brake drum forge. It was rather odd, and after reading this, probably due to my letting the air die while coking. Some of the pops were enough to stir my fire! At least everything stayed contained. It was more amusing than anything

Briefly it sounded like a hit-and-miss engine: pop whuff pop pop whuff pop pop pop pop whuff whuff whuff...kept this up for about a minute, stopped when I gave the fire air. I use a hand crank blower.

When I was tending the fire, keeping the blast going (more or less) and not puttering about getting tools and stock out of the garage it started to behave.

Phil

I know it's to be avoided, but I think this is a cool example of the detonation pentagon (like the fire triangle, but with mixing and confinement, too). At least it's a weak detonation, and the shockwave stays confined within the tuyere. It would be interesting to stick a pressure transducer in there sometime and see just how high it gets.

I use a Champion blower. A couple years back, I had a gas build up and when I turned the crank, I got a nasty backfire through the blower. Made a nice fireball. Thank God it was going away from all living beings! Yep, my son and I got a good scare out of that one. That's the worst one I've ever had.