Hydrogen torch

[Oz]

I’m trying to decide if I want to use a hydrogen torch. Not HHO or Brown’s gas, but a regulated hydrogen/oxygen torch.

What I am lacking is the consumption of gas for the typical melting of gold or platinum effectively in say 5 troy ounce lots at a time. If someone here has used oxy/hydrogen to do this all I would need is the regulated pressure they used for each gas and the orifice size/#size of the tip they used to calculate the max volume of gases used.

Thanks in advance.

 

[pgmgal]

Perhaps these folks can help: http://www.littletorch.com/casting.html

I am looking for another link I had of someone experienced in oxy hydrogen torches.. they sell a DVD re platinum ..ah here it is...http://www.preciousmetalswest.com/

We have only done little bits ourselves.

 

[Oz]

Thank you pgmgal, I had wondered that none here had used hydrogen torches and could give no details.

I have contacted littletorch and they are having their tech guy call me.

I would still be very interested in hearing from anyone with practical experience.

 

[lazersteve]

Oz,

I use an hydrogen/oxy torch for my Platinum melting, but I don't have any data on fuel consumption per troy ounce of metal melted.

I used a rose bud tip with 5 pin holes in the nozzle.

Personally I just fill the tanks when they are empty. I can understand why you would be interested in this information so you can estimate cost verse efficiency of each type of torch fuel. The tanks are very cheap to refill and the cost is negligible on the scale I work. The real expense for me was buying the first tank, hoses, regulators, tip, and safety gear.

Sorry I can't be of any more help.

Steve

 

[Oz]

Thanks for taking the time to reply Steve. It is not cost that I need to know consumption for as I am too cheap to want to buy an additional tank and will make my own hydrogen instead. I currently own all the welding equipment I need for this other than the hydrogen. My concern is the production rate of hydrogen I will require to do the “work” that I wish to do. Although technically a stoichiometric ratio of 2:1 hydrogen/oxygen should be fine, I have heard that in some cases it will require as much as a 4 or 5 to 1 ratio and will plan accordingly for consumption figures as a worse case scenario.

If you know the size of your orifices and the gage pressure you are using I can calculate the max consumption rate for the diatomic hydrogen gas. It would be nice to know the max mass of platinum or rhodium you can comfortably melt in an open dish with these pressures you are using.

Thanks again

 

[lazersteve]

Oz,

I have not tried to push the torch to it's limits so I don't know the maximum troy ounces I can melt at one time with the torch. My biggest Pt melt to date was just shy of 20 grams and it melted like butter in only a few minutes.

With a good steady flame the hydrogen pressure gauge reads between 3-5 psi, and the oxygen is adjusted so the flame doesn't get cooled down by the flow of oxygen. Too low of an hydrogen flow causes lots of popping and too high of an oxygen flow cools the flame. I'm not a welder so I don't know if any of this can be quantified or the reasons for what I observed.

A side note that may be important is that my rig has flashback arrestors on it that caused me a lot of grief when initially getting the torch flame right. Once I had the tank pressure adjusted properly the flame would burn fine. I found I had to crack the seal between the arrestor and the gauge to get the gas flowing.

I also had adjustment knobs on the side of the torch wand to fine tune the flow of H2 and O2 coming out of the tip. I adjusted these for the hottest temperature (fastest melt) with minimum popping/sputtering/whining of the flame.

It would be nice if someone with more experience using hydrogen torches would comment on my observations (arrest, popping, sputtering, whining, proper pressures, temperature vs flow rates, etc.) as I do not have enough experience using one to give sound advice on what is actually happening. Everything I know I learned from experimenting with the torch until I found something that worked for me.

As for tip sizes, again I'm no welder, but the tip I used is about 1/4" across at the tip and has five holes of approximately 1 mm size. This tip was given to me by a friend so I don't have any specs on it.

Steve

 

[Oz]

First things first, I do not have practical experience with a hydrogen torch in hand. I have however talked to a gentleman that used to use one for flame polishing.

With a good steady flame the hydrogen pressure gauge reads between 3-5 psi, and the oxygen is adjusted so the flame doesn't get cooled down by the flow of oxygen. Too low of an hydrogen flow causes lots of popping and too high of an oxygen flow cools the flame. I'm not a welder so I don't know if any of this can be quantified or the reasons for what I observed

Most of what I have read on hydrogen torches indicates that the oxygen and the hydrogen pressures are set the same at the gauges, the volume adjusted at the handset. Your observations as to having too low a mix of hydrogen is in line with what I have heard. Beyond the cooling of excess oxygen I would hazard the guess that with how light hydrogen is compared to acetylene that it dissipates rapidly from the torch tip/gas mix and this is part of the reason for needing as high as a 4 or 5 to 1 ratio for some applications despite the stoichiometric ratio for ideal combustion. I have not heard of anyone using less than 3:1

A side note that may be important is that my rig has flashback arrestors on it that caused me a lot of grief when initially getting the torch flame right. Once I had the tank pressure adjusted properly the flame would burn fine. I found I had to crack the seal between the arrestor and the gauge to get the gas flowing

I have used flashback arrestors for over 20 years for welding gases as a precaution, but with hydrogen this is exceedingly important. I have never had to “crack” a seal at the arrestor to get gas flowing. This is dangerous with acetylene and very dangerous with hydrogen. IMHO hydrogen is a far more dangerous gas due to the increased explosion hazard. Lighting a hydrogen torch can be tricky I have heard. When I asked about this I was told the easiest process was to just crack the oxy valve on the handset then the hydrogen before lighting. Give that a try instead of cracking the arrestor since you have a set-up to try it on. This is rather different than an acetylene torch were you light straight acetylene then feather in oxy.

As for tip sizes, again I'm no welder, but the tip I used is about 1/4" across at the tip and has five holes of approximately 1 mm size. This tip was given to me by a friend so I don't have any specs on it.

Orifice sizes are typically expressed as drill number sizes as in a numbered drill index.

Thanks for your time and input Steve.

 

[lazersteve]

Oz,

I would like to clear up the arrestor problem I was having.

The arrestor was never loosened while the gas was ignited, nor did I ever attempt to ignite the gas with the arrestor loosened. My problem was that when I opened the cylinder valve the gas would not flow out to the handset. This prevented me from even attempting to light the torch.

To solve this problem I found I needed to loosen the arrestor to allow the gas to flow out of the hydrogen cylinder valve. Once the arrestor was 'primed' this way, I tightened it up and I did not have to do this again. The torch could then be turned on and off and ignited normally. I can only assume there was some sort of back pressure locking the cylinder pressure gauge valve so the arrestor check valve would not open.

This problem may have been due to the fact that I had to find a special stem to mate the pressure gauge to the hydrogen tank. The stem was provided for me by the local AirGas where I bought the hydrogen tank. The guy there told me I would have to change out this stem to get the gauges to fit on the hydrogen bottle.

Steve