I'd found this Morgan furnace brochure a month ago which shows a range of "Lift Out" furnaces which is an identical type to what most of us are building. What I find most interesting is that they give performance figures like fuel consumption and time taken to melt a given crucible load of various metals. The fuel consumption figures shown are for the "subsequent melt" which makes sense I guess in a commercial setting. There's a lot of information given including furnace dimensions, capacities for various metals, fuel consumption, time taken to melt and a lot of indirect information to be gleaned about furnace construction from the photos alone. I can see my furnace which can take an A30 crucible (43 Kg bronze) is halfway between the L01 and L02 models but with fuel consumption and melt times closer to the L02 model. It's also interesting that for iron the only choice is a gas start, oil fired furnace. https://www.moltenmetalproducts.com/our-products/furnace/MMP-Lift-Out-Furnace-Gas-Oil.pdf
Also somewhat reassuring that it looks like their fuel consumption rates are in the same ballpark as the roughly 12L per hour rates we here have generally come to believe are about where our furnaces should run. I wonder how their real-world melt times compare with those listed in the brochure. And I wonder how purchasers of furnaces are instructed to determine appropriate air/fuel mixtures to optimize performance. Denis
That would be the interesting part, I guess you could set a given fuel rate and adjust air flow accordingly, maybe use an IR thermometer. The brochure states these are 500-700Kg weight for the smaller two units so you'd expect there's extra fuel used to warm such a mass for the first crucible and which they don't give a figure for, only for the subsequent heats. Edit: The time taken for the first melts are only five minutes longer, so only nine percent longer and nine percent more fuel for the L02 with iron.
That is a great bit of information. Thanks Mark. Their smallest furnace (from what I’m reading) might handle A16... and is 500 kg! Wow. I weighed mine the other day and it is 68 kg (150lbs.), and I could easily fit a A16 (A20 max). I can’t imagine the pump and blower weighing too much. I don’t know where the heck they’re getting all that weight from. Maybe they have 4 inches of dense refractory on all sides.
I just noticed in the brochure: "They are supplied with stand alone combustion air fans and automatic fuel/air ratio controlling devices". It's a bit of a puzzle: "backed by high grade insulation" could mean anything regarding insulation density
Whatever they quote, whatever smoke they blow, whatever lie they concoct, rest assured, none of us will be buying their stuff! The only guy that drops that kind of money is the man concerned with keeping his insurance company happy. The laws of thermal dynamics are pretty much set in stone. You old farts figured out what works long ago and the rest of just copied it. Monkey see, monkey do! If it worked for me, it will work for you.
I would LOVE to sit down with the furnace manufacturer and hear what they have learned in their many years' experience. They must have a huge cumulative experience with fabrication and operation of fuel-fired furnaces. Each of us has a little fragment. Perhaps we should do a group-buy and document the tear-down and user instructions. ;-) I am particularly interested in the fuel/air control system. Does it work right out of the box and does it stay in tune over the long term? Denis
Here's another brochure for the exact same Morgan furnaces which specifies oil viscosity and shows a bit more of the electronic control system for the furnace. It says you can get both manual and automatic burner controls. Like Denis, I'm curious about how the furnace control works: exhaust gas oxygen sensor?, something optical?. http://www.njcjdl.com/manage/newspic/20074423392479549.pdf
Kudos to you for finding more info Mark. I wasn't able to find a single thing. I'd be interested to see the burner construction and atomization. Translating the pressure and viscosity specs it seems that it will run in the range of #2 fuel oil through jet fuel at normal ambient temps @ 20psi. It probably wouldn't run well on the "custom" mix I push through my siphon nozzle. http://www.geotechenv.com/Reference_Pages/average_viscosities_liquids.pdf Pete
Thanks both Pete and Mark for the links. I did read in one of the links that preheating of the oil may be required 35 seconds Redwood #1. This is helping me with WVO.
After doing a little bit of research today... neglecting losses or saturation time... this furnace (The small one) is suggesting 14 L in 50 min (16-17L) . This roughly works out to 160-170 kilowatts per hour. 1 L/h of diesel equals 36, 500 BTU x 16.5 L= 600,000 BTU If I push my two torches to the maximum on WVO I might get 18 L per hour at 30°C . I’ve been testing viscosity with flow rate with WVO. Through a #4 Ford pant viscosity cup. I am getting 7.5s diesel at 24°C I am getting 21s WVO at 24°C I’m getting 8s h2o at 24°C I am getting 66s WVO at - 4°C I could push it harder or pre warm it. Or just not use it.
I guess the fuel viscosity issue is a relative thing, the last few days ambient temperature here has hit 42 degrees C in the backyard. It may be possible to heat the fuel with a thermosiphon water heat exchanger to heat the fuel tank in a hot water bath. I get my fuel pump too hot to directly touch: 50-60 degrees C due to fuel pump churn through the pressure regulator and the need to run the oil pump at a certain speed to get the needed pressure. I have heard of one oil fired furnace that had the fuel line loop near the furnace to harvest furnace heat: it ran great until the furnace was shut off and the nozzle got blocked, the fuel boiled and caused back pressure in the fuel system which was blocked by the fuel pump.... it could have ended badly. So if you directly heat the fuel line there had better be a pressure relief somewhere in the system just in case.
References to theoretical energy required to melt various metals are frequently compared to fuel consumption. You could expect to use 5x-10x more fuel than the theoretical energy required to melt. I think the general discussion of furnace efficiency is an interesting one. It could be a separate thread or maybe this one, but I'd like to see the theoretical energy to melt various metals memorialized and the source of the info, because it needs to include the latent heat at the phase change, not just that associated with the specific heat to raise the metal temperature. After that, the best test of furnace efficiency is the time to melt after the furnace has been brought to temperature divided by the theoretical time to melt, although heating the furnace and crucible are also another level of efficiency for the hobbyist who may only perform one melt per session. Even this isn't a pure indication of furnace efficiency if you are assuming complete combustion, which in many cases is unlikely so burner efficiency enters the overall equation. Best, Kelly
I'd heard of a figure of three percent for a gas fired furnace optimized for speed over all else: fifteen minutes for an A25 crucible of aluminium on the second melt.
I prefer measuring furnace efficiency by how many beers I can consume while waiting. I prefer somewhere around the 2-3 beer mark. Much more than that, things could get dicey!
Well you certainly want to avoid fainting from dehydration while running a furnace....it's thirsty work.
