Natural gas burner questions

[stopwatch]

Hello everyone. I am new to the hobby and looking to set up my first forge. I have natural gas plumbed to my house and I am hoping to use that rather than LP.

That being said, through reading the forums, I know that my house likely runs at very low pressure (0.5 psi or less) and I will have to at the very least have the following things:

-A blower since the low pressure cannot create the flow required for naturally aspirated

-A longer run of piping after the nozzle as NG mixes slower than LP

-I should at the very least have an auto solenoid to shut off gas on loss of power (beyond the manual shut off and regulator)

I read through the design considerations on Wayne coes website and his ribbon burner simply talks about a mixing chamber where fuel is injected. Can I still just use a mig tip nozzle in a design similar to the Wayne Coe example? Can you run  at such low psi? I will have to call to find out exactly pressures. I have seen posts mentioning success with an NG set up, but never in the detail of Mikey or Frosty. I had no luck with the search feature. I have found that NG is clearly not the favorite gas so there are fewer specifics available.

I apologize for the wordy post. Thanks for any help.

[Buzzkill]

With the low pressure that is normal for a residential supply you probably will want to use a larger orifice than a mig tip will provide.  Since there is no need for air induction with a blower, the diameter of the gas supply line is not as crucial, with the caveat that it must be large enough to deliver the volume of gas per unit of time at that pressure needed to provide the desired temperature.  Unless you have gas gauge that can accurately display small increments of a single psi of pressure there will be little advantage to having a small orifice and if it's too small you may not be able to get the heat you want.  I'd probably go with something like 1/4" pipe for the gas if I were doing this, but bigger is not a problem.

Corners help with the fuel/air mix, as does a "chamber" of larger diameter pipe than the supply line which is then reduced to the final burner tube diameter on the other end.   Blown burners are about as simple as it gets.   As long as you have independent controls for the fuel and air supply lines you can quickly and easily change from a rich to a lean burn and/or increase or decrease the temperature of the burner.  The downside is that if you want to maintain the same type of atmosphere (oxidizing, neutral, or reducing), whenever you make a change in either the gas or the air supply  you have to make a corresponding change to the other.   However, by listening to and observing the flames you can very quickly get the hang of what it should look and sound like so these adjustments are not a major issue.

[Latticino]

Buzzkill is correct.  I run residential pressure natural gas with a blown burner on my forge currently.  It is important to size your pipeline from the house based on the amount of BTUH you expect from your burner and the length and number of elbows you anticipate (equivalent length) between the source and the burner assembly as well as any losses anticipated from any valving. My forge is close to 75' from the connection with the pipe line, and is run in correctly rated underground plastic pipe.  I think I used 1.25" pipe underground transitioning to 1" inside my forge.  I expect 1/4" will be far too small, but it all depends on how far you have to run.  No orifice is required, but most blown burner manufacturers transition from the larger supply line down to something on the order of 1/8" NPT for the final connection in the burner mixing chamber to locally accelerate the gas and get good mixing.  This is a great application for a multiport outlet burner head.  Good illustrations for home-made blown burner designs are available in Henry Halem's book: Glass Notes (https://books.google.com/books/about/Glass_Notes.html?id=OI4KAQAAMAAJ&source=kp_cover).  I currently use a commercial burner that is similar to his design, but a bit more sophisticated so I can better control flowrate and atmosphere.

[stopwatch]

Thanks for the responses guys. I will pick up the book to read. When you say you are 75 feet from the pipe line, do you mean the main line or from your home's meter. I'm assuming you don't have a seperate meter for your forge line.

Also the book might go over this but what type of a safety system do you have on your NG forge. Is there any mechanism that is necessary? Just curious about your set up. What commercial burner do you use as I am not opposed to buying although I like the concept of building so that I understand the forge better.

[Latticino]

Here is a photo of my current setup.  The saucer looking item is a zero pressure regulator that allows me to adjust the gas flowrate with the air flowrate from a single air butterfly valve.  I used to use this with a programmable temperature controller to ramp my glass furnace up and down, but haven't set it up for the forge as I don't need it.  Some day I may add temperature control (after I finish up a better forge door)...

The commercial burners are very expensive.  I wouldn't have any except I got several sets by dumpster diving when my school's large glass studio was being renovated.  This one is an Eclipse system, though I have also used others (Northern American???). 

Over 75' from the connection I made to my home system.  A safety system is definitely recommended, at least a gas solenoid valve, and potentially a high pressure gas cutoff.

[stopwatch]

Seems simple enough I suppose. I took a quick look for the book and it appears to no longer be in print. Amazon has informed me I could buy a used one for $440 which may not be worth it. I'll keep looking.

Any recommendations on fan sizing? 

[Latticino]

$440, you have to be kidding.  I used to have (2) copies, one an older edition.  Last I knew it was still in print.  Check the Corning Museum  shop, they used to sell it.  If I still have a second copy I"ll let it go considerably cheaper than $440.

As you can see I use one of the small 140 CFM Blacksmith Depot fans.  Henry's book lists alternatives.  Other source for info may be Dudley Giberson's book (see Joppa Glassworks site).

[Irondragon Forge ClayWorks]

Welcome to IFI... I always suggest reading this to get the best out of the forum. READ THIS FIRST

[stopwatch]

I am trying to spec out some parts. Do you think a regulator is required for residential NG it just a flow control valve. It's already at .5 psi anyway, it's more about volume isn't it.

I'm thinking:

NG connection -> ball valve -> solenoid valve -> flow valve (needle?) -> orifice into mixing chamber

Any issue with this line of thought?? Thanks again.

[Latticino]

Ignoring code issues entirely (which may mandate a regulator for safety against upstream failure of your main residential regulator or the utility supply regulator for the municipality), a regulator would not be required for operation of a typical forced air/natural gas burner.  Don't pick an orifice size from a NA propane burner design.  It needs to be larger to operate correctly.  I think there is an online guide from either Joppa or Pine Ridge for sizing that I posted before, but can't check right now.

Note that your supply pipe will likely have to be much larger than the equivalent supply from a high pressure (30 psi) propane source as well.  This should be obvious, but is often overlooked.  My residential pressure NG forge has a 1" gas supply pipe.