Pre-Flight Your Siphon Burner

Discussion in 'Burners and their construction' started by Melterskelter, Dec 3, 2018.

  1. Melterskelter

    Melterskelter Silver Banner Member

    7416849A-C6AB-41B1-89F4-3571945A4D1B.jpeg B17AFA92-03F3-443C-8AAF-CE521397673E.jpeg I have recently learned through hard experience that it is useful to check your burner fuel flow prior to firing it up. I run a Delevan nominal .75gal per hour siphon burner which is really suposed to burn 3 gallons diesel per hour. I have probably used it for something like 100 or more melts but the last couple melts it seemed to burn slowly as the iron in the pot just seemed to come up to temp much more slowly than expected. Given that there are three variables in play—-combustion air, atomizing air, and pressurized fuel flow, it can be a bit of a head-scratcher if the furnace seems to be heating slowly.

    Clearly with my last melt things were just running behind schedule, but I hated to shut down mid melt to troubleshot. But immediately after the melt, I disassembled the siphon nozzle and found some blobs of “crud” blocking a couple of the air spin-grooves and also a partial obstruction of the fuel port. I suppose this stuff gradually accumulated and then finally became obvious.

    Prior to disassembly I turned off the atomizing air and left the fuel pump on so it was providing 9 pounds pressure to the fuel. I observed the fuel flow and took a pic.

    After cleaning out the crud I rechecked the fuel stream and noted the stream arched out about 8 feet compared to a weaker stream that arched about 4 prior to cleaning. (Reminds me of 9-year-old boys peeing over the fence ;-) ). The top image is after cleaning with no atomizing air and the bottom is pre-cleaning and no atomizing air.

    I have decided that each time I setup to melt I will test fuel flow with air off and then test atomizing air effectiveness to be sure that things are operating according to plan. I have an idea that would be a good practice for general adoption if it is not already standard practice. In addition I bought an in-line air filter (should have had one from the get-go) and put it just upstream of the air-in connector and moved my in-line fuel filter downstream so it is just up from the burner connector also.


  2. Mister ED

    Mister ED Silver Banner Member

    That's a good post Denis!

    I guess I never gave an air filter a thought, definitely a good idea.

    Just before winter set in, I bought the parts for a new pressure tank. I bought a stainless 5 gal soda fountain keg, a 0-25 psi (or so) gauge, and converted over an old inert gas regulator to regulate tank pressure. The reason I did so, was even with diesel I was having issues siphoning, once my tank level went partway down (nozzle was clean). I will also head your advice on cleaning that nozzle before each run. Assuring the fuel flow is always consistent takes out one of the three variables.

    That second pic looks like the 9 year old hit the hot wire of the fence. ;-)
    Last edited: Dec 4, 2018
    Melterskelter likes this.
  3. Jason

    Jason Silver Banner Member

    Looks like it's taking a piss.
  4. Melterskelter

    Melterskelter Silver Banner Member

    Just for clarification that air filter is on the compressed air line not the combustion air. I doubt anyone would have been confused, but who knows...

    I am also ordering tonight a fuel flow meter so that I can monitor the fuel burn rate. That should reduce the chance of blockage of the nozzle going undetected and will allow me to tweak burn rate for optimal performance. Finding a fuel flow meter in the desired relatively low flow rate range is not easy. Aircraft use such a device but, naturally, a device certified for aviation use is quite expensive---on the order of 300 to 1000 dollars. However I did find this


    I should receive it in a couple days.I will post about it once I have installed it and tested it out. Probably should start a new thread at that time devoted to the fuel flow meter.

    This sensor will allow continuous monitoring of fuel flow rate in LPM and will allow me to see the flow change immediately on changing needle valve settings (hopefully). One reason I bought it through Amazon is that returns are relatively easy should it not work out and delivery was much faster than ordering from Hong Kong or China though it is identical to sensors and displays available from those sources.

    Last edited: Dec 3, 2018
  5. PatJ

    PatJ Silver Banner Member

    I have about 40 pours using Delavan siphon nozzles, but not all on exactly the same nozzle.
    I have not had one clog yet, but I could see how they could clog.
    I use an in-line fuel filter and burner clean diesel fuel.
    If I were using waste oil, I would use a spin-on fuel filter to give more surface area, and I would make sure the waste oil was strained through a fine mesh.

    You could change to a 1.0 gph nozzle to give you marginally more clearance, but I doubt it would make much of a difference.

    My air compressor has an intake filter, but it is not a bad idea to add a portable filter/water separator near the burner, since you can accumulate junk in the lines some times.

    I worry about sludge build up in the nozzle, but I have never seen it occur.
    If it did sludge up, it is easy enough to unscrew the nozzle and clean it.

    I keep a spare nozzle too so that I could make a swap in perhaps 5 minutes during a melt if necessary.
    When my pumped nozzle burner is operational, I will use the siphon nozzle as a backup unit.

    I looked at fuel flow meters, and I found one that I liked, but the factory would not guarantee that it would work with diesel, so I did not buy it.
    If the internals are not diesel rated, then the rubber-like materials can swell and cause things to stop working.

    I have figured out a way to circumvent the fuel flow meter though, and that is to use a Toro multi-speed leaf blower on the lowest speed.
    I know that the lowest speed provides exactly the amount of air required to burn 2.75 gal/hr (which is what my burner operates at), so if the flame coming out the lid is not exactly as I expect it, and I cannot adjust the flame with the fuel needle valve, then I know I have a fuel flow problem.

  6. Zapins

    Zapins Silver

    Subscribed. That device looks fancy af. I've never had good luck with siphon/oil burners so this thread is interesting to me. Maybe one day I'll figure out how to get mine working.
  7. Lately I've been connecting everything for the fuel system right up to the nozzle and then flushing into a 20 litre pail, after that I connect the nozzle and see if it's spraying ok before plugging it into the tuyere. The leftover fuel gets filtered back into the fuel tank.
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  8. Melterskelter

    Melterskelter Silver Banner Member

    I thought of increasing the nozzle size, but with increasing fuel pressure I can get all the heat I can use.

    I like direct measurement of fuel if possible. The sender unit may or may not be OK for fuel as I have seen it listed both ways. If it is not OK, then there are other 10 dollar senders that are sure to be OK with fuel. All the sender does is produce pulses which are counted by the display and then shown as liters with the "K-factor" adjustable for the ratio of pulses per liter so that various senders can be used with the same display unit.

  9. PatJ

    PatJ Silver Banner Member

    This flow meter appears to have a range of 15.8 to 476 gph, so with a 3 gph flow rate going to your burner, you will not register any flow on the meter, if I am looking at the data sheet correctly.

    The only low flow meter I could find was this one, and it has a range which could be used with our 3 gph flow:
    But Omega would not verify that it could be used with diesel, so it would be an expensive gamble.

  10. Melterskelter

    Melterskelter Silver Banner Member

    Sorry to be slow to respond---I had back-to-back melts (55 pounds and 40 pounds) today one of which finished after sunset. I love evening pours---so beautiful. (One thing I have learned to do for night pours to help my crucible-dazzled eyes to see the pouring basin and sprue is to sprinkle a modest amount of talc on the them. That makes them much more visible given the near black color of the rest of the mold sand) The day was crisp but dry and in some ways the perfect kind of day for melting. And back-to-back melts save so much time and fuel.

    I want to see how the unit I ordered actually performs as I have found the specifications for this and similar units to vary some---maybe difficulty with translation from the way the original specs were written. Anyway here is a not so promptly available but very similar in function unit that is said to be OK for fuel that is said to measure 0 to 10 LPM flows. These units all seem to use Hall Effect pulse generation to count revolutions of a wheel or gear. So, I will not be surprised if the one I linked will measure very low flow. But, that should soon be evident once I get a chance to test it. Similarly, fuel compatibility is sort of an open question. If it won't do the job, I'll just wait a little longer and order one of the sensors linked here and use it with the counter I will already have. There were about 20 listings for just this brand sensor on eBay.

  11. PatJ

    PatJ Silver Banner Member


    You are the energizer-bunny of iron casters.

    I hope the flow unit works for you, but I am skeptical of it having any sensitivity with that wide of a range.
    I have not used any product like that so it is just speculation on my part.

    Good luck with it.

  12. Melterskelter

    Melterskelter Silver Banner Member

    Learning, learning, learning, learning ;-)

  13. PatJ

    PatJ Silver Banner Member

    Nothing outpours the Energizer, they keep pouring and pouring and pouring and pouring............

  14. Melterskelter

    Melterskelter Silver Banner Member

    After posting my query about flowmeters on another forum I was informed of the availability of a simple transparent nylon flowmeter "for water" that is highly chemically resistant (code for almost certainly would work with diesel but likely would require some calibration adjustment due to density and viscosity differences).

    A few things I like about this style flowmeter:
    1)Simple---tapered tube and a ball. No batteries, power supplies, moisture issues, short circuits etc
    2)Inexpensive---30 bucks
    3)Compact---2" in height
    4)Robust---not easy to break a nylon thick-wall tube

    Cons: needs to be mounted vertically but does not leak if tipped when moving it etc.

    Look at the MMA 40 model here:


  15. PatJ

    PatJ Silver Banner Member

    That is an interesting product.
    Not particularly accurate at (+-) 4%, but accurate enough for what you are trying to do.
    I think it has potential.
    Not sure how the fluid temperature will affect it, but diesel has a pretty low viscosity relatively speaking, compared to waste oil.
    Would not work with waste oil since you would not be able to read the scale.

    If you order one, let us know if it works.

  16. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Accuracy or precision may not be as important as repeatability for MS' purposes.


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