LP gas configuration to melt gold

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yazeed

Active member
Joined
Jan 18, 2010
Messages
27
Recently in looking for an alternative gas configuration to melt gold and also seeing the disadvantages of the blowtorch to melt gold,a shopkeeper advised me on another alternative to a handheld gas device.It uses normal LP gas canisters with a torch attachment with a claim of reaching 1800°c,so guys do u think this arrangement for melting gold would work and how long would it take in minutes to melt a small average button
 
yazeed, Lp can be propane or butane or a mix of these liguid petroleums, I will speak of propane here:
propane can get hot enough to melt gold, some of things to consider is what gold is being melted in, if open air and melting dish and a torch heat is lost to surrounding airand even the dish, also what dish sets on can act as a heat sink to absorb heat, furnace refatory can absob heat some types more than others, but refactory surrounding can also help to contain the heat and reflect heat back as radiated heat (a double edge sword), also a furnace has the ability to give you better control of the enviroment of the melt (oxidizing or reducing atmosphere), the burner (or torch if used) will also make a big difference, there can be a dramatic differenc in their construction, how well they burn fuel with air, flame character, and heat produced and type of flame they make, also burners can be desighned to run at different gas pressures, some are assisted with blower's providing more air (and fuel for hotter temp), some burners may also be desighned to convert liquid fuel to gas (heated coils at burner head, with some fuels like propane or fuel oils), well we could go on and on, hand held propane torch is very useful with what we do, but lack the heat needed in my opinion for melting gold outside of a furnace, hand held torch flame can also be small compared to furnace burners, but if I was wanting to melt gold with propane a furnace in my opinion is needed, and a burner that fits furnace size .these can easily be built with scrap yard material, a little welding skill and refactory, burners are also easily made, or these can be purchaced, to me they are so easily made I cannot see no reason to buy one.
backyard metal casting, propane burners, propane furnace, and like terms will lead you to much information on google, also these have been discussed many times here on the forum and pictures are here on the forum of different desighns, as well as induction furnace discussions.
hope this helps some.
 
I have found that I can melt gold with a handheld torch using MAP gas. If I switch to propane (same torch head and crucible, etc) I cannot get it hot enough.
If I, however, place the crucible in my furnace and use the handheld with propane, I can melt the gold. The furnace is a simple "peach can" style furnace but a little bit bigger with the addition of a small round 1/2" thick firebrick in the bottom on top of 1" of Kai wool. The sides and too are,1" wool as well
 
Hi
I want to use LPG in gas cylinder for melting silver
Can someone check my homemade torch before I use it ?
Is it completely safe ? :?

I added a flashback too but it didn't work so I remove it. Is it safe without flashback?

Thanks

http://uupload.ir/files/r0fd_img_20170809_203925.jpg

http://uupload.ir/files/6ikw_img_20170809_204110.jpg
http://uupload.ir/files/sfap_img_20170809_204204.jpg
http://uupload.ir/files/lr95_img_20170809_204222.jpg
 
Hi
Yes, all of flashbacks here are for acetylene gas or oxygen. I use acetylene flashback but it didn't work
Maybe LPG doesn't need flashback?!
Is it dangerous ?

http://www.gcegroup.com/files/images/Product%20Images/INDUSTRIAL/FBA/80910_Oxygen_80950_Fuel_SG2_MV93_hose_thread_torch.jpg

Edit:
I find this in web:
https://www.quora.com/Why-dont-we-provide-flash-back-arrestors-for-cooking-gas-cylinders

Whereas, in the case of Cooking, flash backs will not occur. Here, LPG is in pressurized form, whereas the oxygen (in atmosphere) is at the atmospheric pressure. Hence, there is no possibility of oxygen or explosive mixture entering LPG cylinder. So, a Flash back arrestor is not necessary for a cooking gas cylinder.
When you perform oxy-fuel cutting, both the oxygen and fuel gas cylinders are pressurized. Flash backs are commonly caused by a reverse flow of explosive mixture (of fuel gas and oxygen) through hose into either fuel gas cylinder or oxygen cylinder.

Hence, we provide flash back arrestors for gas cutting operation.
But we use blower instead of oxygen cylinder. Can a blower blows air in gas cylinder? For example when pressure in gas cylinder is low?
 
I have worked on industrial burners (boilers) (with many different fuels), and been in the welding trades, and worked on many different types of appliances that use either natural gas or propane.

But when it comes to propane burners, and what we should need to know about them, especially when dealing with safety, I am no expert, so take what I have to say, with caution concerning this matter.

I have built many of my own small burners for my personal use.

My thoughts on this (take with grain of salt)]:
With a propane (or natural gas) if the burner is properly designed there should be no need for the flashback arrestors.

In a torch that is a totally different matter, I would use flash back arrestors. The torch (cutting or welding has a different design and it works differently and the conditions are very different from burners.

Acytelene will explode if pressurized (not sure at what pressure but somewhere above 15 PSIG), With a much higher oxygen pressure, and a mix of acetylene and oxygen and the back pressure of a flashback or sustained back fire, in the torch you can be standing next to a bomb trying to melt a little gold. so use flash back arrestors and check valves on your torch.

Propane under Normal working pressure does not explode (like acetylene will) it can be compressed to a liquid, as that is what is in your tank (the liquid under pressure drops to a lower pressure environment in your burner to become a gas(actually gas fill the small volume of the tank inside but lets not get too technical here).

In a properly designed burner, the propane is forced through a small diameter orifice (very small hole say a # 56 or #62 drill for example) the gas flows into a stream of air (from a blower or from the venturi effect of the burner itself) or even a stream of oxygen. The burner is not really under much pressure (even with a blower, (compared to a torch and its design). So the likely hood of mixing fuel and oxidizer (in the gas line or in the tank) is not likely to happen (my opinion only). If it did get oxygen or air into your tank I do not believe there would be much of a problem (again keep the salt handy).

As far as burn back or flash back in the burner, here any safety device would never be a bad idea.
But I really cannot see the burn back entering the fuel line or the tank through the orifice in the burner design (torches again is a totally different story).
A flashback is different than a sustained burn back or backfire.

For a moment lets discuss torches (I may get back to the burner).
In A torch:
Most of the causes for a flashback or a burn-back (back fire) are normally operator error, using the torch wrong (overheating), damaged (seats), loose or leaky fitting or damaged parts in the torch.

Burnback or backfires are normally less dangerous (than a flashback) the burning back of the flame inside the torch tip (Loud popping or snapping noise) as the flame goes out, will rarely get past the mixing valve to (create a flashback).

The Flashback can be much much more dangerous! here the flame (similar to small high-pressure explosions) burns back past the mixing valve (sounding like squealing pigs, or hissing snakes) as the flame pops out the torch tip spews clouds of black sooty smoke, if you get flash backs something is seriously wrong with the torch (need repair of faulty condition) or it is from how you are using it (overheating, too close to work, using wrong pressure setting...).and as mentioned earlier with acetylene it becomes explosive somewhere above 15PSIG (note the red line on yer gauges).

The burner (of course this depends on the type, but for what burners most all of us on the forum would use) is much different from the torches we use.
The burner will not suffer the same issues, as the torch.

My recommendation is Always Use check valves and flashback arrestors on your Torches.
Although a flashback arrestor and a check valve could never hurt and would be a smart safety feature, the flash back arrestor is not totally necessary on a "properly designed burner.

Now saadat68,
As far as your burner and what I can tell from the picture, I do not see any obvious safety issues.
But as far as the design I see some things I would change, (they may not be needed as I have not used or tested it), (so again we may need some salt, with my words), the delivery pipe looks very long (may or may not be a problem, but I feel the pipe from the blower should be bigger in size (you want a good volume of air, and little restriction, (maybe even sizing it as big or bigger than the fan blower outlet).
The galvanizing (zinc coating) from galvanized pipe (if that is actually what you are using) is a big NO NO, Zinc burns and oxidizes easily and emits white spider webs into the air. I have had night sweats chills where you feel like you are dying from welding on Zink coated steel (galvanized steels). Use black iron pipe.

I am no expert by far, and only can go on what little I know or believe, so take it for what it is worth (not much), do your own research. just my own opinion on the matter.
My safety is in my hands, and your safety is of yours, my friend.

A few Tidbits on propane, I would look for more myself and study as much as I could on the matter.

https://gashosesandregulators.com/propaneregulatorfacts.php
http://www.harrisproductsgroup.com/en/Expert-Advice/Articles/Flashback-Arrestors.aspx

Propane approximate vapor pressure of liquid at various temperatures:
-20 deg. F ----10 PSIG
0 deg. F ------23.5 PSIG
+20 deg. F ----40.8 PSIG
+70 deg. F ---109 PSIG
+ 110 deg. F---197 PSIG

Note also the more volume of gas delivered from the tank the colder the tanks get( multiple burners, large burners long use time a large volume of flow), it is not uncommon for the tanks to freeze or develop a frost from the refrigeration effect of the liquid changing to a gas (high-pressure liquid to a low-pressure gas) where it may be necessary to sit propane tank in heated water or use a heater blankets...
 
Thank you very much butcher

I got these from your post:

1- Burners and torch are different. So burners don't need flashback arrestors but a torch such as welding torch needs.

2- The burner is not under much pressure even with a blower so there is no risk that oxygen goes in gas tank. Also you think there isn't any problem if oxygen goes to propane/natural gas tank
(Even gas proportion in tank is 5 or 10 percent and pressure is low?)

3- burn does not back entering the fuel line or the tank through the orifice in the burner design (Likely I added a suitable nozzle in the pipe. Is it in the right place? )


As butcher isn't contain that his post is fully correct I need someone confirms his and my posts

Thank you
 
saadat68 said:
I added a flashback too but it didn't work so I remove it. Is it safe without flashback?

Thanks

Had a similar problem with my oxy/propane setting, after getting back to the shop where i bought some of the parts, mechanic took a look at my setup and turns out problem was very simple - the reductor (regulator?) on my propane tank was wrong kind - giving out enough pressure for propane stove (where it was originally from) but not enough for my brand new torch setup (not enough to pass flashback arrestor), i got a new reductor (relatively very cheap) and my torch worked beautyfully, actually melted my first button today :).. . Will try to upload pic tomorrow :)

Anyhow my advice is to solve flashback arrestor problem, oxy/propane flame is suprisingly powerfull, one can only marvel at the awesome power contained in those two little tanks...
 
Thank you niks neims

You use oxygen too but I don't. I use blower instead it also as butcher said propane does not need flashback arrestor. I couldn't find arrestor for propane, all of them are for acetylene and oxygen.
Something is wrong. :?

I go to shop today. hope to solve problem with another regulator
 
Try a larger (air pipe) blower pipe or burner pipe, for the fan size you have.
Check the orifice size (fuel hole size) for propane (try drill number #56 to #60).

Check (pressure regulator) for burner size.
Try 0-20 pound propane adjustable regulator.

https://propanewarehouse.com/shop/propane-regulators/adjustable-propane-regulator-0-20-psi/
 

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butcher said:
Try a larger (air pipe) blower pipe or burner pipe, for the fan size you have.
Check the orifice size (fuel hole size) for propane (try drill number #56 to #60).

Check (pressure regulator) for burner size.
Try 0-20 pound propane adjustable regulator.

https://propanewarehouse.com/shop/propane-regulators/adjustable-propane-regulator-0-20-psi/

I can buy this:
http://www.avijehsanat.net/Images/Original/0257c8c8-1986-4a99-a479-9b5a2b7fa40b.jpg

It is 0-3 bar
3 bar = 43.5 psi

P max of flashback arrestor is 1.5 bar. No problem ?
What happen if regulator set in 2 or 3 bar? Does flashback arrestor work In this condition? ( these regulator don't have any gauge )
 
I am having some problem understanding the comment or question, things get lost in translation.
And I am also trying to get into my head the conversion of these pressures (bar pressure is unfamiliar to me).

Bear with me here.

1 Bar = O PSIG (pressure we read on gauge) = 1 atmosphere (pressure of the weight of air all around us) = 14.69 PSIA (absolute pressure, most people do not read on gauges) = 101.3 kPa ...

1.5 bar = 21.75 PSIG(gauge pressure).
2 bar = 29 PSIG (gauge pressure).
3 bar = 43.5 PSIG ( as you so well put it).

OK now that I have that solved in my head lets see if I may be of any help.

First make sure the regulator is for propane, regulators are made for specific gases, specific density, and internal parts of the regulator can be very different for different gases or liquids...
Using the wrong type of regulators can be very dangerous.

A drop of oil in an oxygen regulator or even on oxygen fittings can cause an explosion, many types of pipe sealants use oil, so on oxygen the sealant or even tape should be made for use on oxygen.

You most likely will not go over around 20 PSIG (< 1.5 bar) with your burner and still maintain a good flame and not freeze up your tank (Where the vapor pressure would drop).

Propane approximate vapor pressure of liquid at various temperatures:
-20 deg. F ----10 PSIG
0 deg. F ------23.5 PSIG
+20 deg. F ----40.8 PSIG
+70 deg. F ---109 PSIG
+ 110 deg. F---197 PSIG

About 20 PSIG for the flashback on propane sounds correct (that is about what the capability of your burner would be) if designed and sized properly, The flashback is normally open until a back pressure (from a small explosion of pressure occurs), then the flash back closes quickly (much faster than a check valve can), the flashback is also much more sensitive than a check valve. It will still close under a greater pressure with no problem, but at below 20 PSI rating it will not close, so at 2 to 3 bar the flash back would still offer protection.

With your burner running greater than 1.5 Bar (if it could without problem), the flashback would still do its job, and would not slam shut, the burner would not build that pressure inside the burner to give back pressure to the flash-back arrestor.

Again here is where the design
of the torch differs from the burner, the torch would build back pressure enough to overcome the flash back spring setting and would shut off the fuel supply, until the pressure wash lowered, or the flashback event was over(explosion was out and the pressure in the torch dropped below the flashback setting.

If you wish to see the pressure you can always plumb in a gauge into your system with simple tee fitting...
Most of the time I see no reason, but it would be a nice feature while trying to design your burner or monitor its actions and reactions...

I hope this helps, again with your safety ,check what I say with other resources, I may not always be right in what I say.

I am not sure if you are abbreviating words, if so please spell them out, it becomes a big problem with translations or understanding of comments or questions. and it is hard enough for us to understand each other as it is.

With the long pipe and small air pipe the burner in your picture could act more like a torch, make the blower pipe bigger, I would also put the fuel orifice fitting closer to the burner tip. look closely at the picture I posted above.


good site lots of information on homemade burners and forges.
http://www.backyardmetalcasting.com/oliverburner1.html
http://www.backyardmetalcasting.com/index.html
http://www.backyardmetalcasting.com/blowburner01.html
 

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Thanks a lot
So I will buy 0-3 bar regulator and hop it works
And also buy 3/4 or 2/3 inch black iron pipe for blower
 
Fortunately it works
I changed pipe too
http://uupload.ir/files/470z_img_20170813_205821.jpg

-------------

I have a question for future
I want to use natural gas lines instead of cylinder in next year. I tested flashback arrestor in my home with natural gas line and it doesn't work because gas pressure is very low. I don't need flashback arrestor in these lines. right ?

http://uupload.ir/files/tdx6_img_3906.jpg

http://www.istgah.com/images/2017/04/21/1846772_k6z0FQ_r_m.jpg
 
The burner looks much better in design.

If I Understand you.
You said it is working now.

I would like to see a picture of its flame, to see if I can tell if the flame is oxidizing (good blue inner cone) or a sooty yellow flame. if you do get picture try it in dark light so picture shows flame good.

The burner, if it works well on propane will work just as well on natural gas, you will just need to change the fuel orifice size (hole at fuel tip).

I notice you have large traps on your gas lines (we use traps here also) but not that big or P trap shape (here we just make a small one with plumbing fittings a tee and a pipe nipple and cap to clean them out. your gas lines must be much more dirtier than ours or have more rust or water???

I am also wondering what the long white material the roof has is it insulation or some type of white brick?

I see no tee where the fuel line goes into your 1-1/2", 2" or 3" pipe, did you just drill and tap it for threads (or welded)?
Or is it put together yet? I cannot tell from the picture. make sure you have no leaks there.

The same thing with the flash-back arrestor, with natural gas as we discussed with propane, not needed for your burner, but a good safety feature to have.

Make sure to use good hoses rated for propane,or the gas you use the burner on, make good connections with no leaks. A leak in the hose next to you and your furnace (well you get the idea).
Some gases can make glue out of some types of hoses...

Give us some details of sizes of pipes, orifice size (hole in fuel port end) and so on. Posting details will help other forum members reading this, and wanting to build themselves a burner.

Looking forward to seeing your burners flame, good job, maybe we can get past (at least some) of this language barrier.
 
Thank you butcher
My burner need some welding and a valve for working. I will add some images after completion
I mean my flashback arrestor works.

What is trap ? Do you mean gas meter ?
https://en.wikipedia.org/wiki/Gas_meter

Gas in here is clean and I think it is butane or much of it is butane. We say to this gas lines , city gas.

Those white materials are :
https://www.google.com/search?biw=1093&bih=510&tbm=isch&sa=1&q=styrofoam+roof+panels&oq=styrofoam+roof+&gs_l=psy-ab.1.0.0l3j0i30k1.5745.5745.0.7058.1.1.0.0.0.0.207.207.2-1.1.0....0...1.1.64.psy-ab..0.1.207.bs3Fdhtgyd8

That house in image is not complete and I added it from google image
I take a picture from my home :
http://uupload.ir/files/0bmc_img_20170814_124346.jpg

sizes of pipes:
Gas pipe is 1/2 inch
Blower pipe is 1 inch

Orifice size:
I don't know what is it's size. Here we have 2 model orifice . first model is for city gas and second is for cylinders gas. Orifice hole of city gas is bigger than cylinder gas. I bought one of them and add to my pipe with fitting
https://cdnimg.webstaurantstore.com/images/products/main/110664/192940/all-points-26-3947-burner-orifice-80-liquid-propane-13-32-27-thread.jpg

http://www.netwelding.com/Orifice%20in%20Fitting.jpg
 
Thanks for satisfying my curiosity.
The holes in the fittings are what I call an orifice natural gas is bigger than propane, we use drill sizes here, and I make my own for the burners I build, your gas is probably not much different than ours we may just use different names.
What I call a trap is the U shape in the pipe, used to trap dirt, rust. water...
If you can get the pipe cut and threaded you could use a 1"X 1/2 tee (1' both ends, 1/2" in middle) with teflon tape to seal threads.

The web site I posted has good information on the jet or orifice sizes, and regulator pressures...
 
First I want to say I decide to remove flashback and high pressure regulator because there is very very high pressure in hose and always I see leak. This is dangerous and I prefer use low pressure regulator.

In other websites that I checked there isn't any flashback on their hose for example :
http://www.backyardmetalcasting.com/blowburner01.html

-------------------------------------------------
Today I weld pipes and test burner. Something is wrong
http://uupload.ir/files/04k_img_20170822_173610.jpg

When I used high pressure regulator (that I don't want use it again) I got these flames:
http://uupload.ir/files/uzcj_img_20170822_172340.jpg
http://uupload.ir/files/y548_img_20170822_172232_burst5.jpg

If I add more air the flame turns off. I couldn't get neutral and blue flame
--------------------------------------------------
When I used low pressure regulator like this :
http://www.backyardmetalcasting.com/blowburner01.html

I got just a small and yellow flame like a big candle! Sometimes I got blue and yellow flame with air adjusting but it turns off rapidly
What is the problem ? Maybe my pipe is too large ? (It is 1-1/4 Inch)
 

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