Removing the O-Ring from a Delavan Siphon-Nozzle Oil Burner

Many burner types have been discussed online over the years, and everyone seems to have their favorite burner for their favorite reasons.

One drawback of a Delavan siphon-nozzle is that it has an o-ring built into it, and while I have never melted an o-ring, I do pay careful attention and either withdraw the burner from the furnace when I turn it off, or leave the combustion blower running if the burner remains in the furnace.

While I like the simplicity of a drip-style oil burner and have very seriously considered building one, I don't want to give up the fine/instant control that I get from my Delavan siphon-nozzle oil burner, and so while tedious, I will make the changes to eliminate the 0-ring.

This will allow me to skim and/or add ferrosilicon with the burner off and the crucible in the furnace, without worrying about the o-ring getting overheated.

So here is my scheme for omitting the o-ring.
A bit involved, but I think it will work well, and the tip of the nozzle will still be replaceable should it ever get damaged.

 

I'm wondering how RTV silicone would work as a thread sealing material: it works up to 350 deg C versus 250 deg C for teflon. I made a conventional brass nozzle today, I plan on having an aluminium crush washer seal between the two components, with maybe silicone on the 1/2" UNF thread.

 

The first step is to drill out the adapter.
This photo shows a drilled-out adapter (on right) beside an original adapter (on left).





The oil entry hole in the side of the adapter was drilled larger and a brass plug fitted in the hole.











The end of the adapter drilled out. Be sure to drill out the correct side. Both sides look exactly the same, but they are not.
The nozzle will only screw into one end of the adapter.





A piece of tubing was purchased, and was silver-soldered onto the adapter.











A piece of steel brake line was purchased and silver soldered onto the small part that is inside the nozzle (the part that can be unscrewed).








The small spin vane is added back onto the unscrewed piece.




The small piece was screwed back into the outside piece.





The tip and associated brake line were screwed back into the adapter.









A compression fitting was drilled so that the brake line can pass through it, and the fitting was installed on the brake line.




A plug was welded together to go at the outer end of the burner tube, and a few fittings were added to it.




A brass nipple was drilled through and trimmed off to make a sort of gland nut.
If this joint is not entirely airtight, it will not matter since it only sees the pressure produced by the combustion air blower, which is very low.
I welded a steel pipe nipple on the end of my compressed air tube, which is not ideal since I would have to cut it off to remove the tube, but that is the only idea I had.





The compressed air valve is added.




The fuel needle valve, ball valve, and inline fuel filter are added.
The needle valve will be calibrated to give a 3.0 gal/hr flow rate and then fixed by tightening the gland nut.
The fuel ball valve will be used along with the compressed air ball valve to turn the burner on and off.
I guess it is obvious, but the oil flows in the brake line, and the compressed air flows in the 1/2" steel tube.
The interior parts of the burner are secured to the burner tube using a stainless steel band.
The band originally came with a rubber insert, and I discarded the rubber piece.




A support bracket was welded onto the burner tube.




The ball valves will be attached to the bracket, and this will prevent the brake line from getting bent or damaged.




I cut some fins into the end of the burner tube, and I don't know if they will work well or not, bit I thought I would try them to help with the mixing of the fuel and combustion air.
I think I am going to add three screws at 120 degrees to support the center tube, and this will allow me to adjust the nozzle and get it in the exact center of the burner tube.
My intent was to make the combustion air spin counterclockwise to match the small spin vane in the nozzle tip, but this orientation may spin the air clockwise.
I am not sure which direction is better for spinning the combustion air.
Edit: The burner seems to work ok without the fins in the end of the burner tube, so I may omit these on future burners. The fins tend to deform the end of the burner tube and can create problems when inserting the tube into the tuyere if the fit is tight (as it should be).

 

I am not sure, but I do know the furnace gets extremely hot when doing iron pours, and anything near its interior needs to have a pretty high temperature rating, ie: the melting point of silver solder or something along those lines.

 

True, I think I'll use a copper crush seal rather than aluminium.

 

Hopefully I can get if finished up tomorrow and do a test burn.

 

I think that would work well.

 

Looks good, I look forward to the video of it running.

 

Video; right, I need to remember to make that tomorrow.

 

Don't forget to charge the batteries too!.

 

Charge batteries (note to self).
Got it.

 

I am getting ready to test the revised burner tonight.

As I was fitting the burner into my tuyere extension last night, the extension sheared off, since it was not cast integral to the hotface shell.
I was not sure at the time how to cast the extension at the same time as the shell, but I think I know how to do it now, and if I cast another hot face shell, I would definitely cast the tuyere extension at the same time.
Not really a problem, the extension can be cemented back in place, and it acts mainly as an extended seal for the burner tube, to prevent blow-by at the tuyere from the pressurization of the interior of the furnace with the combustion air blower.

But the good part about the extension shearing off is that I can play around with the vertical angle of the burner.
I think oldironfarmer? recommended angling the burner tube down a few degrees to keep the flame lower in the furnace, so I will try that.

I will calibrate the burner to 3 gal/hr before I light it.

I am also interested to see if the spin vanes that I cut into the end of the burner tube will actually spin the flames, and if so, in which direction? (clockwise or counterclockwise).
When I have used spin vanes in the past, they have produced a visible spinning flame, but I have not used a spin vane in several years since I considered the ones I used as too restricting to the flow of combustion air. These vanes hopefully will allow enough combustion air for 3 gal/hr, otherwise I can bend the tube back straight again and remove the vanes.

I am not sure if the spinning flame will actually affect the burner/furnace operation, but the commercial oil burners do have spin vanes, although they are discharging into a much larger space at a wider angle.

If this goes well, then I will proceed with ramming the refractory for the lid, and then we should be ready for more iron tests/pours.

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I got the re-worked burner running tonight, and learned some very interesting things about operating a burner that I wish I had learned about 4 years ago.

I had a few false starts.
I hooked up the air and oil lines, but no fuel would flow.
No problem with delivery from the tank, so I knew it had to be the dreaded silver solder creep, and indeed that is exactly what happened.
When I silver soldered the small piece onto the brake line, the solder flowed into and sealed the small opening in the end of the part.

I disassembled the burner, drilled out the piece, tapped on the piece to clear out all the chips, and put it all back together.
The fuel flow started, but then slowed down considerably.
Failed to clear all the chips out of the brake line, so disassembled the burner (again), turned on the fuel, and flushed out ALL the chips.

Sipon-nozzle burners are not tolerant of trash in the fuel, which is why I run an automotive fuel filter.
If you use fuel with a lot of trash in it with a siphon nozzle burner, you better have a good filter, and probably a spin-on pre-filter, and a secondary automotive inline filter.

I have never had any clogging problems since I have always used an inline filter and run clean diesel.

So I got the burner running in free air, and took some videos.
I calibrated it to 3 gal/hr, and everything worked as is should.
I could turn on a little bit of combustion air outside the furnace, but not much, else the flame would blow out.

I will post the video of the exterior burner operation in a few minutes.

Edit:
Here is a video of the burner operating outside the furnace:


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The next step was to test the burner with the furnace, and this went well.
I angled the burner down a few degrees, and varied that up and down a bit, and it seemed to slightly help keep the flame down in the furnace, but it was not a big change from horizontal to angled down slightly.

I started with the lid off the furnace, and once the burner got started, I added the lid.

I did not vary from the 3 gal/hr fuel flow rate, but I did try varying the combustion air flow, to see whether the furnace ran hotter in a lean, neutral or rich setting.
In the past, an iron melt was always attempted after a hectic day of making molds, dragging out and setting up equipment, cameras, etc., with a lack of time, and generally darkness setting in during the melt.
So typically I would start the burner, adjust what seemed like a good flow rate (generally too much flow rate, like 5-6 gal/hr), and then cranked in a significant amount of combustion air (too much combustion air).
The iron would get red but not melt, and so I would start changing the fuel flow and combustion air flow in a random fashion, generally with very poor results.

Occasionally I would get the air and fuel settings correct, but it was an accidental success, and not something resulting from knowing exactly how to adjust the burner and combustion air.

So tonight I stuck with 3 gal/hr, and did not change that.
The only thing I changed was the combustion air flow, and I took my time, and just watched the furnace for a long time over a wide range of combustion air settings.

When I added a large amount of combustion air, the furnace and crucible visibly cooled off, and the interior furnace surfaced went from bright red to dull red.
I tried the other extreme with considerable blue flame coming out the furnace lid, and the furnace ran hotter than with too much combustion air.
And lastly I tried a medium amount of blue flame coming out the lid (not sure why the flames where blue, but they were), and it was at this setting that the furnace very obviously ran at its hottest temperature, with a bright interior glow and a red hot crucible.

There have been a number of discussions here about optimum fuel/air ratios to produce the hottest temperature, and I understand that there is an optimum point which runs hottest, but actually observing that while a burner and furnace is operating has not been an intuitive process for me, and as I mentioned above my iron melts have always been too rushed an affair with a lack of attention to small details.

At one point I started to build a multi-flow set of valves to control fuel flow, and experiment with various fuel flow levels, but then discovered that several people who were having a lot of success with iron were running about 3 gal/hr, so I decided to discard the multi-flow idea and stick with a fixed rate of fuel (3 gal/hr).

I can't really explain what is happening when the optimum heat is reached, other than to say that the fuel flow is significantly rich, and this seems to create a very hot combustion process from the bottom all the way to the top and out the furnace.
Thermodynamics was not my strong point in school, but suffice it to say, I finally figured out how to get the maximum heat out of a burner.
I am very surprised at how little air it takes to produce maximum heat. I had to valve off most of the output of my leaf blower, and the leaf blower was running on its lowest speed.
All those big blowers that you have seen me and others use are totally counterproductive. Big blowers are quite effective at cooling a furnace.
What is really needed is a small blower. Less is more.

I have no double I can melt iron in a relatively consistent way after tonight's tests.
I think the final pieces of the puzzle have been sorted out, at least as far as getting the furnace hot enough to melt iron in a reasonable amount of time.

I have videos of the burner running in the furnace at various settings, and will post a link when I get them uploaded.

Here is a video of the burner running in the furnace.
It starts with oil and compressed air only, and then the combustion air is turned on.
The mixture was varied from lean, to neutral, to rich, to very rich, and it seemed like the rich setting (with the blue flames outside the lid) made the furnace run hottest.
Towards the end, the burner was turned off, and the hot-restarted.



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Edit:
I hand-lifted the lid on and off while the burner was running tonight, and it actually worked fine and without wearing leathers. The trick is to lift the lid and swing it away from the furnace in one quick motion. No problem; it worked well, and nothing overheated in the process such as my gloves, etc.
I am not sure I would recommend hand-lifting a lid to the general public, but is is quite feasible and no real safety issues that I saw.
I generally place the lid on a raised metal bbq grille to minimize shock on the hot surface.

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Edit 02:
I could not detect a difference in the burner operation with the spin vanes cut into the end of the burner tube. I guess I will leave then in place for now and do a few iron melts, and then try the burner with them straightened out (no spin vanes).

 

I drilled three holes in the burner tube at 120 degrees, welded on some 1/4-20 nuts, and added bolts to allow precision adjustment of the burner nozzle inside the burner tube.
My burner is not exactly a precision instrument, and so nothing on it is exactly straight.
The three bolts do a great job of aligning the nozzle exactly in the center of the tube.

 

Here is the burner operating in the furnace.
The flame spread seems relatively even with the burner tube angled down a few degrees; not a huge change but perhaps a bit better.

 

Some odd things were happening with the furnace and burner tonight.

Generally the flames coming out of the furnace lid are yellow when the mixture is rich.
Tonight they were blue.
It could be the stainless refractory needles protruding out slightly into the furnace interior are causing the color, or the fact that I was not using my tuyere extension (so I could adjust the angle of the burner) and so the burner tube protruded slightly into the bore, causing the blue tint.

My general understanding before tonight was that the hottest setting for the burner was one in which all the fuel is completely combusted inside the furnace.
After watching the furnace tonight, it seemed obvious (from the brightness of the glow of the furnace interior) that the rich setting with a blue flame above the lid produced the hottest furnace interior.

If there is a blue flame above the furnace, then that means that some of the fuel is combusting outside the furnace (the burner is operating rich, or with excess fuel), and so the hottest setting apparently is not when all of the fuel is completely combusted inside the furnace.
Perhaps the rich setting allows the combustion process to occur from the bottom all the way to the top of the furnace and completely out the lid opening, thus exposing the furnace interior to the maximum amount of the hottest combustion.

Also, this furnace seems to make it easier to detect which burner setting produces the hottest furnace, I guess because the low mass reacts much faster to a change in heat, and the increase in the intensity of the glow is easily noticeable.
Or it could be that with my old furnace, I just did not know exactly what I was looking at when trying to adjust the burner.

The only thing that was modified in both videos was the combustion air flow (via the dump valve located on top of the leaf blower); otherwise the same 3 gal/hr fuel flow rate was used for both tests.
In the past, when I was trying to adjust my burner, I randomly adjusted both the needle valve (fuel flow), the compressed air pressure, and the combustion air flow.
Making random adjustments to a burner (unless you have a lot of experience operating one) is not a good way to learn how to make it operate at its maximum.

For both tests, the compressed air pressure was 40 psi, and 10 psi was used to pressurize the fuel tank.

I think I will try one more test tomorrow with the same 3 gal/hr fuel flow, and see how low I can set the compressed air, and observe what happens with lower and higher compressed air levels (while maintaining the same rich setting, ie: blue flames above the lid).
It would save wear and tear on the air compressor if the burner was operated at as low a compressed air pressure as possible.
It would also be interesting to see if the compressed air pressure could be reduced to zero, and the burner operated in drip-style mode. (Edit: No, this does not work).

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It looks like you have a fully working iron melting furnace, it's interesting that the flames are blue: I'd heard of that anecdotally but have not seen it. I did see video of soap bubbles of hydrogen being burnt with an orange flame on Youtube: I thought you had to have carbon burnt to get orange flames. The castable refractory looks to be about 1.5 inches in that last photo:, it's hard to judge the scale of the objects in that second last photo (for me): is the orange drum a 20 litre 5 US gallon can?.

 

Yes, that is a 5 gallon bucket.

The cast refractory is 1" thick. The shell weights about 70 lbs, and the top weighs about 30 lbs.

Inside dimensions of the furnace are 13" diameter, 14" tall.
I ran it without the insulating fire bricks around it, and without the stainless outer shell, so it looks a bit odd.

The outside stainless shell is about the size of a 55 gallon drum; about 22" diameter.

I think I made a lot of progress tonight.

 

Darn right you made a lot of progress!, you're almost over the line. It's good to see such a relatively thin refractory getting quite hot considering I have a bit over 2" or 50mm for my furnace.