Found Dreaming

I thought this warranted a post of its own.

As I was working with my evaporator burner today, all was going very well. I had just poured a pot, returned the crucible to the furnace, closed the lid and bricked it over to keep in heat. I was now relighting the burner for as second run. The evaporator was heated up, so I turned the oil on. A mist of vaporized oil naturally drafted into the furnace without the blower. As I reached over to turn the blower on in a calm and collected manner- BANG- the vapor in the furnace exploded.

Apparently, by complete randomness, the right air to fuel mixture was in there and something provided ignition. I swear that the lid jumped a bit. I have a big furnace and a light lid, so its not impossible. I really jumped. It sounded exactly like one of the big band cannons I have.

The moral of the story- LEAVE THE LID OFF WHEN RE-LIGHTING ANY SORT OF GASEOUS FUEL BURNER. It doesn't matter that its veggie oil- its a gas at that point and a highly flammable one. All you propane guys hopefully know this, but I don't think you would think of it with an oil burner like this.

It was certainly funny, but not exceptionally safe and would easily get metal casting privileges revoked for some of us.

Now the qestion- would this also happen with plain old atomizers?


Bill

I have gotten some pretty good booms on my furnace. Did you shut it down to pour? I leave mine on the entire time while I am casting which would be anywhere from 4 to 8 hours most times.

I turned the oil off, but everything was still smoking hot.

I would just leave it running while pouring especially if you are going to do another melt and even if I am going to shut down I return the crucible then shut down. My setup runs very low with little heat blowing up out the top with the lid open though and from pictures I have seen of a lot of folks oil burners where there are flames lapping up out of the top it might make more sense to shut down when reaching in with tongs.

You are right on about leaving the lid open to relight though, no need for that kind of excitement around molten metal.

if you want to prevent further bangs (I had some in the past as well) let the blower run for a while after you killed the oil flow that will prevent the buildup of explosive oil vapors

I just don't like the idea of throwing cold air into a hot furnace...my hotface is already cracked. The navy foundry manual also warns against it.

I would just leave it running while pouring especially if you are going to do another melt and even if I am going to shut down I return the crucible then shut down. My setup runs very low with little heat blowing up out the top with the lid open

I do the same thing, I always leave the furnace running until after I've put the pot back in. It is one less thing I have to turn off / do before the pour.

I'll have to get in that habit then. I always pour at least twice too so why bother shutting it off.

Thanks for this post. I never would have even considered that. You probably just saved me from blowing myself up. Thanks again

Barry