New to me furnace and new problems.

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Lazz
Posts: 131
Joined: Sun Jul 29, 2012 11:06 pm
Location: The Warm Arizona Deserts... Phoenix to be precise...

New to me furnace and new problems.

Post by Lazz » Tue May 21, 2019 3:55 pm

I found a Pyramid #8 furnace in new unused condition.
When running molten metal comes out of the vent.
https://imgur.com/a/34PwyYv

Adjusting the gas or air does not seem to effect the problem. Opening the lid partially fixes the problem.
Pictures on the internet suggest the vent is small.

Any suggestions?

Harold_V
Posts: 17618
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: New to me furnace and new problems.

Post by Harold_V » Tue May 21, 2019 4:06 pm

While I am not aware of any particular rule that determines how full you should use a crucible, I can't help but wonder if, maybe, you are filling yours too far?

I've never had the same problem with the furnaces I've operated (all home built), but I also didn't melt aluminum. I strongly suspect you wouldn't have the same problem with heavier alloys.

A larger opening would likely slow the exhaust at the port, but the distance between the top of the crucible and the lid is likely the reason you have the problem, as the gasses are running quite fast to get to the exhaust port. You may enjoy success by adding a gate valve between the internal port and the blower, so you can control the amount of air introduced to the furnace. It will then demand less fuel, and increase your melting time correspondingly, but that should solve the problem. Needless to say, you'd also need a valve on the fuel, so it can be balanced as well, although you may already have that feature. You might also discover that the plinth can be made shorter, increasing the space between the crucible and lid.

Damned shame you had to go through this and damage the lining.

H
Edit. I just re-read your post and see that you said that controlling the air and fuel doesn't make a difference. I find that strange. Raising the lid results in slower discharge, and less air supplied should do the same thing, especially if you can lower the crucible a little.
Wise people talk because they have something to say. Fools talk because they have to say something.

Lazz
Posts: 131
Joined: Sun Jul 29, 2012 11:06 pm
Location: The Warm Arizona Deserts... Phoenix to be precise...

Re: New to me furnace and new problems.

Post by Lazz » Wed May 22, 2019 12:44 pm

Thank you for your reply....
I found the problem last evening. Firing the furnace in the dark provided the clue I needed. The propane was not regulated. Flames were invisible in day light but at night they were several feet above the vent hole. Im guessing the flames burning outside of the furnace created a vacuum and it sucked droplets of ammunition into the air.

It was the regulator.
The new regulator I bought from Amazon is more of an on off valve than regulator. Full blast or nothing no matter what the position of the knob. I swamped it out with another off the shop heater and fixed the problem.

The aluminum droplets cleaned off the furnace easily this morning so no damage to anything.

Thank you again.

Harold_V
Posts: 17618
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: New to me furnace and new problems.

Post by Harold_V » Wed May 22, 2019 3:15 pm

Nice troubleshooting! Also good to hear that there was no damage to the lining. Looks like a nice little furnace.
I'm facing the build of one----although larger. I have several crucibles, some of them still in the box, which I hope to put in service if I live long enough. So many projects and so little time.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

FKreider
Posts: 50
Joined: Fri Feb 02, 2018 8:44 pm
Location: Sturbridge, MA

Re: New to me furnace and new problems.

Post by FKreider » Tue May 28, 2019 6:57 pm

I own a Pyramid #10, very cool to hear of someone else owning one, I think they are relatively rare these days.

What size crucible are you using in your model #8?

Mine came with a very used #6 crucible which I use for aluminum and I just purchased a new #5 which will be for bronze only.
-Frank K.

Lazz
Posts: 131
Joined: Sun Jul 29, 2012 11:06 pm
Location: The Warm Arizona Deserts... Phoenix to be precise...

Re: New to me furnace and new problems.

Post by Lazz » Wed May 29, 2019 8:28 am

There were 4 new crucibles in the deal, 3 #8 crucibles and a #10. And 2 new silicon carbide plinths
The #10 is a tight fit but it does fit.

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