Furnace Drain Holes---Procedure for use?

This is an interesting discussion with good points on both sides of the drain vs no drain option.

I think I will see if I can have a setup that includes a plugged drain with a simple lever that will allow pooping the plug out if needed. I'll be melting iron over a sand surface, so having the liquid metal pour out might be better than it freezing in my furnace along with the plinth and broken crucible. I do have a Salamander Super, so hoping this does not occur, but....

At least that is my thinking so far as that addresses the controllability issue and potentially reduces the damage related to crucible failure. Does this sound like a practical approach? Maybe use pottery kiln peep hole kiln plug? I am not sure of the temperature limit on such a plug. Use refractory disc with a bump that roughly fits into the drain hole? Copper plug?

Denis

 

Why not just add a small round piece of steel to make a drain cover and attach it to a pivot and handle.

When a crucible fails just swing the little gate open for it to drain out.

 

Wouldn't you expect the steel to just scale like crazy at those temps---not quite melting but close to it? When I heat treat steel at only 1700, it scales pretty badly in only an hour if unprotected by a stainless envelope. A stainless cover might be OK, I suppose. But not sure how even stainless would do at 2700 degrees or so.

Denis

 

for the record...I have a 2" drain hole but it's covered with the plith that has a cross pattern groove. I haven't seen any flames coming out the bottom.
I use a cast iron skillet setting atop a steel can lid to catch what may come out the drain.

 

Other than my drain being smaller than yours, this is my experience as well. There has been times when I haven't bothered replacing the tinfoil plug I choose to use and don't notice anything getting passed the plinth. Now during a direct melt, (the forgotten benefit) I definitely see flame pushing their way out the bottom. I use steel crucibles for melting aluminium and use the drain as a means to remove rust/scale out after a melt.

It was commented on earlier about fluid fuel dripping out the drain. I run waste vegetable oil via drip burner and only use propane as a preheat. I did experience oil dripping out the bottom early on in my burner building efforts. It also seeped between the seam of my hot face body and base. Once I had the burner sorted out and learned how to use it, I had no further pooling issues. If you fluid fuel can puddle on the bottom of your furnace and then subsequently drain out, the drain shouldn't be considered the problem. In fact, I'd call it a bonus that you don't need to sob up the pool inside the furnace. An ingot tray will catch fluid oil just as well as it will catch fluid metal.

The notion of not wanting a spill to exit the furnace isn't something I can argue against if you believe it provides a greater aspect of safety. Different strokes different folks I suppose. Personally, I always leave an ingot tray under my furnace drain. Mainly because I was originally melting over an asphalt driveway and would rather not deal with the molten whatever damaging it. Now, I still follow the same practice. Force of habit I guess.

The assumption that the use of quality equipment and pre-melt checks will negate the advantages for a drain is fool hearty imo. I've used similar analogy earlier but buying a car with collision detection doesn't mean you should go without wearing your seat belt.

If you rather house a spill, then drain it, well no argument here. That said, I'd rather be melting down my newly accidentally made ingots then spending my weekend chipping out the frozen metal in my furnace.

 

I was talking about attaching it on the out side of the furnace on the bottom.

I don't see that getting hot enough to scale..... But then again I could be wrong as I've never tried it.

Just a thought.

 

I see. Somehow I imagined you were talking about a steel door located inside the furnace combustion area. I suppose one that butted against the outside of a drain hole would be less exposed to heat and scaling.

Denis

 

The lasts suggestion is very similar to the 'door' seen in a forge air blast pipe used to remove clinkers. Usually hinged and weighted.

 

Screw the drain hole.... Take a chance in life. Go Commando!

 

Ask the guy who went bungy jumping after an Indian takeaway

 

Over the course of time the hole will get filled from incidental metal unless it gets cleaned out routinely. That's just one more step to forget at pouring time. Once it's full and solid, it's not likely to melt back out. Even a hole left open can plug up because of incidental metal or use in a direct melt if it's not looked after. I've had my 1" plugged several times through the use of failing steel crucibles and less-than-judicious maintenance. The use of charcoal lends to it as well. A 1/2" drill will get it opened, and since I'm not using steel or charcoal anymore I feel that crucible failure is unlikely. Being more careful about what I'm putting in the crucible helps too. Over-length material is always the culprit. Yes, it will lower itself in as it melts, but just because I can doesn't mean I should.
Both of my crucible furnaces shoot flame out the hole like a rocket engine with both propane and oil burners. Even with the plinth in place. I plugged the hole in the small furnace from the inside with a mixture of sand and fireclay. Having some sort of ejector pin for it seems like a good plan.

Pete

 

I have a strange habit... I like to vacuum the inside of my furnace before I use it each time. Same goes for the kiln. Don't know why, but seems like a good idea.

 

I always just chuck a pussy cat or 2 in there before placing a crucible in the furnace.

A little VooDoo seems to help keep the hole from clogging up.

 

Yup, headless chickens work as well OCD...

I am thinking with a plinth on the bottom of the furnace, I am going to try about 1/2" of sand on the bottom. Not sure it will help in a release of hot metal but it may make things easier with splashes from drossing tools etc?

 

That's given me an idea. For reasons I don't want to go into, I accidentally encased my last plinth in aluminum. I've beat the living hell out of it with a 3# hammer and the plinth hasn't budged or cracked. Maybe I'll try a direct melt.

 

reply

 

So, I melted the thing.
got my plinth back.