Melt time?

This is mostly a point of curiosity.

What sort of melt times do you get?

I'm running 50/50 waste oil and Diesel through a 0.75 GPH Monarch nozzle. Refractory lined beer keg foundry.

Just completed a melt of 15lbs of Everdur.

Roughly speaking, it took me half an hour to get the foundry up to temp (with propane) so the oil could take over.

From the point it was running good and hot, it was right at two hours until the metal was at the point of initial melt. Took another 45 minutes from there to get up to casting temp.

I'm looking to find out if I should work out some way of improving my burner/foundry situation, or if what I'm getting is pretty much on par for what these setups will deliver.

Any thoughts?

 

The inner diameter is right at 11". The working area is right at 13" tall.

 

Yeah, solid refractory. IIRC, it was called "Vesuvius".

 

I do not use propane to start my Diesel burner. I run 2.5 GPH through a .75 GPH Hago siphon burnet. I melt iron 30 pounds in 40 mins and 50 pounds ready to pour at 2550 in 90 to 100 mins. I think that is about on par with other folks. I pressurize my diesel at 9 PSI and at that pressure have to close the needle valve a lot to keep flow down to that rate. I atomize at 25 PSI and run a modest blower on my combustion air. My key to proper-tuning of air/fuel is to have a hint of reddish flame coming out the exhaust. Too much air(no flame) =cold furnace. Too little air (big yellow flame) = cold furnace Getting that mix right is crucial. My furnace is medium density, a combo of thin dense refractory an a wrap of wool.

Denis

 

I’m running a 1 GPH delavan siphon nozzle with similar pressures as Denis. I run primarily waste oil. I preheat with propane, but I usually switch over to oil after about 10 minutes. My furnace has a 10” bore and 2.5” solid walls (1” mizzou backed with 1.5” sand/fire lay). It’s not a real speedy heat-up, but 15 lbs of bronze would take me about 60-70 minutes from a cold start. A second heat would be about 20 minutes.
Do you have pictures of your setup Jeff?

Pete

 

Here is a link to a forum thread discussing melt time, which links to another forum thread discussing melt time:
https://forums.thehomefoundry.org/index.php?threads/melt-time.1651/#post-37486

 

Inside, it looks like this:



The fuel mix sits on top of this setup:



Other than the siphon action and the elevation from the fuel jug, it isn't pressurized. I didn't measure it exactly, but judging from the drop in the level in the jug, I'd guess I went through the 0.75 GPH that the nozzle says. More or less, anyway.

The air pressure is provided by my cheapo HF 21 gal, 2.5HP compressor. I have the regulator set to the max, which is about 110lbs. When the burner is running good, the compressor is really getting a workout. I timed it yesterday and for every five minutes, it is running for three.

(I do wonder how long that thing is going to hold up...)

The furnace itself looks like this:


In terms of getting it dialed in, what I get is that the needle valve for the air is just barely open. Like 1/8 of a turn. Same thing for the fuel. That one runs at something like 1/4 turn open. In fact, that's been the hardest part of this. The air in particular seems so incredibly sensitive. The tiniest adjustment to that can cause the burner to blow out. Denis' comment that he atomizes at 25 pounds makes me wonder if I'm doing this all wrong and need to dial down the compressor a bunch.

My technique for dialing in the air/fuel ratio is this: I run it rich initially. I know it's rich because the walls of the chimney soot up. Once it's running good, I slowly turn down the fuel until the walls turn white. My assumption was that I want to run this on the lean side. (In the hot rod world, we have a saying: "Too rich leaves power on the table. Too lean leaves pistons on the table." I've always equated "lean" with "hot".) I can tell when it get's too lean because the burner will "pulse". So I turn it down until it starts pulsing, then turn it back up a smidge until the pulsing stops.

Here's a video from yesterday with the thing in action:



One thing I wonder about: That block in the bottom that the crucible rests on...how tall should it be? The way it is currently set up, the top of that block is pretty much even with the bottom of the port that the burner goes through. In that way, the direct flame ends up hitting pretty low on the crucible. Any thoughts on that?

Anyway, that's what I can tell you about what I'm running here. Based on some of the melt times you guys are talking about, I suspect I've got a lot of room to optimize things. Appreciate any ideas/advice!

 

Lean is hot in an engine but not necessarily in the furnace. The problem is that you’re literally loading tons of air into the furnace and having to heat it up. So what needs to happen is to get optimal furnace heating is to get just enough air to nearly completely combust of the fuel but not quite. Don’t make the mistake so many have of blasting way too much air into the furnace and then wondering why it’s cold. My own experience is that using just enough compressed air to not have buildup of coke in the furnace allows Sufficient atomization for good combustion. Then you just add in enough blower air to get the flame appearance that I mentioned. Maybe that won’t work out just right for you but I sure would give it a try and see what you think. It took me a long time to tumble to this.

Denis

 

Good stuff, Denis. I'll give that a shot and see how it goes.

Thanks!

PS: Did a little digging and found this spec sheet from Monarch. We'll see how the test goes, but this table agrees completely with what you're saying. I've been running at WAY too high of pressure!

 

Yes, many of us use more than the manufacturer recomemended atomiztion air because we are pressurizing our fuel and runningfmore than the nozzle is designed for. That extra fuel flow needs extra atomization. For 2.5 to 3 GPH, 20 to 25 PSI seems to be just enough to get full atomization.

Denis

Added: BTW, I’m practicing what I preach. This photo taken moments ago:
Fuel pressure 9.5PSI. Flow rate .19L/M

25PSI atomizing air.

The general crime scene.

All done 1:40 mins later. 55 pounds poured. Pouring basins glowing and molds smoking.
l

 

All good stuff here so far.
A couple of things to consider. As Denis mentioned, we are trying to burn way more than .75GPH. We (you and I at least) are burning fuel that is way thicker than #2 fuel oil which is what I think those nozzles are rated for. Denis is running straight diesel for the sake of consistency, and I sure don't fault him for that. That's how he's able to light it without preheating with propane as well. At any rate, thicker fuel will require a greater amount of atomization air, but 100PSI is off the charts. I started burning oil with an unpressurized fuel tank utilizing only the venturi action of the nozzle just like you are doing. I found several aspects of that setup to be limiting, mostly insufficient fuel delivery as well as combustion air sensitivity. Outside of increasing the height of my fuel tank and thereby increasing head pressure, the only other way to increase fuel delivery volume is by increasing the compressed air. Therein lies the balancing act. You'll get a marginal increase in fuel but a great effect on the amount of air in your furnace. As an aside, I believe there is a certain point at which increasing the compressed air no longer results in increased fuel flow, but I have nothing to backup that theory. By using a pressurized fuel tank the issue goes away for all practical purposes. You can find the amount of pressure necessary to atomize, and the optimal amount of pressure to deliver the amount of fuel you want independently and repeatably (is that a word?). I use about 15PSI with my 1GPH nozzle), and about 20PSI pressure in the tank. With these settings I have the ball valve for the atomizing air full open and my needle valve on the burner for the oil open just over 1/2 of a turn. I start with the needle valve somewhat lower when switching over from propane to oil, but once I'm up to temp I end up at just over half a turn.
The next thing I was thinking deals with the o-ring in the nozzle. You can cook that o-ring if you're not careful with it. Propane burning back up into your burner tube could do it, but based on how you have your propane coming out of the nozzle, that doesn't seem likely. Leaving the burner in the furnace with no fuel or airflow can destroy it as well, so checking that o-ring and having replacements on hand is a good idea. I actually replace my somewhat frequently. If you're trying to run with a bad o-ring it will certainly affect the fuel delivery. A final thought is that running the atomizing air at such a high pressure may actually cause the nozzle to not function correctly by getting past the o-ring. Again I have no proof of that, just a guess at the possibility.
Running with just the nozzle's venturi action will work, clearly. If running straight diesel you can light right off with it and can actually melt a pot of aluminum without ever turning your blower on. Adding a pressurized fuel tank just takes some of the variables out.
Pete

 

Sounds like the next step in all this is to figure out a way to add pressure to my fuel flow. That makes sense.

I'm trying to think of the simplest way of doing that. Here's the first thing that came to mind. Get a basic HF air tank (like the kind you use to carry compressed air to a remote location). Cut a 2" hole in the top and weld in a threaded 2" black pipe nipple so I have some way of adding fuel. Cut a 1" (or whatever it is) hole toward the bottom on one of the ends and weld in a 1/4" NPT black pipe nipple for the outlet.

Anyone try anything like that? Seems almost too easy, like I'm missing something.

 

I use a Holley fuel pump in my setup. It is enclosed in the wood box above. You have to be sure whatever pump you choose is diesel compatible. Not all are. The nice thing about the pump is all I have to do is pour/siphon additional fuel into my 5 gallon fuel tank without interrupting the melt. No need to break a pressure seal. Most fuel pumps have an internal bypass limiting their pressure output. Not all do. Mine required no bypass over-pressure reducing line. Just fuel and fuel out plus 12V which I supply with a 120AC-in/12v DC-out power supply (cheap.) If you pressurize your tank, its pressure will continue to drop as fuel leaves the system. You will have to figure out how to prevent that.

I like having fuel pressure guage on mine as that is a simple check to make sure the pump is doing its thing and that there are no supply restrictions---found a kinked hose that way quickly the other day. Also the flow meter you see is really nice to have. Once you have one variable nailed down in the air/fuel mix issue, tuning gets a whole lot easier and reproducible melt-to-melt.
Most folks do not use flow gauges. But I really like it and would not be without it.

Here is a link to the meter I use. http://forums.thehomefoundry.org/in...with-a-pelton-sensor-and-digital-readout.811/

As near as I can tell all the cheap garden and home flow meters are useless at low flow even though they claim to be low flow meters. I tried a couple and wasted time and money on them. This meter has been bullet-proof and is well-documented. Plus its pinout is in the thread I linked! ;-)

Denis

 

I use a retired gas hot water tank. I could have used one of the small ones but I went with a 50gal cause that’s how I roll (plus that’s what was available at the time. Lol.) It has exactly the right number of holes already in it, including one for a pressure relief valve. Did I mention the pressure relief valve? I didn’t have to strip the skin off it or anything! Bonus! I run air into the hot side and it pushes the oil up the dip tube and out the cold side, through an automotive oil filter, and then on to the furnace. The air comes in from the bottom quick connect from my compressor and out through the top to the burner nozzle outside. I’ve since added a regulator to the outbound air and also replaced that little hose barb with a garden hose fitting to fill the tank. Everything is obviously stationary and my lines run outside through a hole in the wall of the barn.


Pete

 

Ok, now we're getting somewhere!

This is what I ended up coming up with:



Just finished my first melt using that, and WOW! Totally different ball game.

The biggie is that the transition from propane to oil was effortless. I used to struggle beyond belief to get the oil burning right. Tonight it was nothing.

(I've never before completed a melt where I only had to light the furnace once.)

I've got to go dunk my flask, but wanted to thank the forum first! It is such a blessing having your help. Can't tell you how much it is appreciated.

 

You already have a solution but wanted to post this idea up for those people looking in the future. I don't have the opportunity to have "forum time" like I used to and have way less experience than Petee and MelterSkelter (haven't had much time for that lately either). But when I was starting and after having issues with the variability of siphon nozzle & diesel, MelterSkelter helped me see the light on reducing the number of variables (both through post and messages).

My solution, I purchased a Corny Keg for my fuel. I control the air pressure to the keg via its own regulator ... I think I have it center lined at 7psi. Without looking, I think I have my nozzle air center lined at 20psi. Now I have only one variable to mess with, blower air. Less variables = more consistency.

One potential issue is if I need to refill my keg, I cannot do that on the fly and would have to shut down to refill. The 6gal capacity has not been an issue yet, but there may be times when I might need to plan accordingly.

Oh, for the Corny Keg fittings, I did have to change out the o-rings to a petroleum resistant material (Buna-N I think).

 

Oh, yeah ... to save some others from looking ... Corny Kegs are a stainless tank that fountain soda syrup used to come in. Quick connect fittings, relief valve, designed to be pressurized (albeit low pressure). Basically a beer keg for soda.

I am guessing anymore most soda probably comes in a box.