Frequently asked questions

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Frequently asked questions

Q. What size Propane regulator do I need to run a 3/4" atmospheric burner? A.Gas Forge Propane Regulator sizing.   Everybody keeps saying that you need a 0 to 30 High Pressure Regulator and they leave out a very important factor. The BTU output of the regulator needs to put out at least 100,000 BTU,s for each 3/4" burner that it will be hooked up to. A lot of the so called 0 to 30 high pressure regulators only put out 40,000 BTU. The same goes with the POL fitting it needs to be capable of 250,000 BTU output. This is very important information when building a gas forge.

Q.  What is the best method for coating the Ceramic Blanket once it is inside your gas forge?  A. Forge coating instructions

 Step 1: Apply an Ins-tuff Ceramic Fiber Rigidizer
The first thing you need to do to the ceramic blanket once it is installed in the forge is coat it with a Rigidizer,  this provides a harder and more resistant, but less resilient, surface on the material being treated.

Step 2: Apply the Kast-O-Lite 30 coating
Mix the Kast-O-Lite 30 to a thick paste, just keep adding water slowly until you get a pasty consistency that you can paint on with a paintbrush the consistency of sour cream. Spray the ceramic fiber insulation down using water with a hand spray bottle to wet it lightly if you are putting it directly on the ceramic blanket and not using a rigidizer. If you use a rigidizer first you do not need to moisten the blanket.  Next, apply the Kast-O-Lite 30 to the wool using a paintbrush, covering all exposed wool surfaces. To cure it, you want to dry it slowly when installing a lining, we do like to seal any insulation back up prior to casting against. Any insulating product will be porous and may pull moisture from a cast lining. While we have used mortar to seal these areas, we have also utilized sodium silicate. You are looking to add a barrier to seal the surface so the back up lining does not act like a sponge. This is one of the reasons that you put a good coating of Rigidizer on the ceramic blanket before applying the refractory  When casting refractory products, you have a cure period after casting. This is generally 24 hours. We have found for low cement materials, it is best to cover them to hold the moisture in and prevent the surface from drying out to quickly. It is best to cure evenly. If these type of products Cure too rapidly, the surface will crust over then must crack to allow moisture to dissipate through the surface. I am sure if you google concrete curing, you will find that it may be best to cover with moist burlap and mist water over a period of time. This is to prevent the surface from taking a set prior to the lining curing evenly. The same applies to other castables.
When it comes to dry out, the slower you can dry a product, the better the properties are. You are trying to soak heat into the product to remove moisture. The lining gains strength when this occurs. The deeper you can soak heat into the lining, the stronger the product will be.  Then fire up the forge just briefly and shut it down. Do this several times, allowing it to cool down in between and increasing the on-time with each subsequent cycle. You'll see water vapor evaporating the first few times you do this. Finally, fire it up and bring it up to full temp to cure it fully. You will probably want to apply at least two coats of Kast-O-Lite 30 in this manner,it's a little time consuming but makes for a more robust coating. A 1/4" layer is a good thickness to shoot for. If you are going to apply Plistix 900F over top of the Kast-O-Lite 30, be sure to fully cure the Kast-O-Lite 30 first.  

The same procedures described above can also be used if you are going to use Satanite or Greenpatch 421 instead of the Kastolite 30 LI using the same guidelines.  I personally use The Greenpatch 421 coating because of the following.  It is a premix and Air Set, this is better because it cuts out a lot of the user error involved with ceramic coatings.

Step 3: Apply the Plistix 900f coating Plistix 900F
Mixing Instructions:  (Note) This method is for if you are applying the Plistix 900F directly onto the ceramic blanket and not first coating it with a rigidizer or Kast-O-Lite 30.  Plistix 900F is in a powder form and is mixed with water to the consistency of a thin milkshake it is then applied to the refractory by dabbing it on with a paint brush, brushstrokes tend to pull the fibers apart. It does not dissolve so it must be continually stirred during use.
Application Instructions:  If you are applying the Plistix directly on the ceramic blanket you can mist the blanket with a little water to help slow the drying. The Plistix can be coated over Loucast 3000, Kast-O-Lite 30, Satanite, Rigidizers or other high temperature coatings.  Make sure the ceramic coating is dry before applying the Plistix Drying and Curing Instructions:  After the Plistix installation is complete, Plistix 900F may be left to air dry for an indefinite period as long as freezing does not occur.  It is recommended that chemical setting Plistix 900F be prevented from air drying for any significant amount of time prior to bake out.  If an extended time interval between installation and bake out is expected, longer than a week cover the chemical bonded plastic surface with plastic sheeting or use a liquid membrane concrete curing compound to keep the plastic moist. Once material has air dried to a hard set your forge is ready to use.  The first firing should be done with a low flame allowing the refractory to warm up slowly to avoid thermal shock .
Q.  What are the inside and outside diameter of the burner flare that fits on 3/4" pipe?     A.  The
nominal inside diameter of the  flare is 1.049 and outside diameter of the large end of the flare is 1-3/8”.

Q.   How far should the flare stick into the forge?   A.  The flare should not extend down into the forge chamber it should be up inside the Durablanket about a 1" to help protect the flare from the high heat in the forge chamber.

Q.   What size pipe do you use to mount the side arm burner assembly?   A.  For the 3/4" pipe burners I like to use 1 1/2” schedule 80.  You can also use 1 1/2" schedule 40 pipe if you want, the schedule 80 is just a little thicker and gives you more a few more threads.

Q.   Does the Modified Side Arm burner require a blower?    A.   No, this is an atmospheric burner, it does not require a blower.

Q. What is the purpose of the burner flare or flame holder on the end of propane burners?    A. To keep the flame from blowing off the burner's end by lowering the pressure of the incoming gas air mixture.   This lowered pressure also prevents the flame from burning its way back up the mixing tube.

Q. I am building a round body forge out of pipe, what is the best location for the burner or burners?   A. The best location for the burner is 10 to 15 degrees off top dead center.   This helps to prevent the heat from radiating up the burners.  Plus it helps to create a swirling action of the hot gases inside the forge body.

Q. What size opening should I have in the ends of the forge and can I close off one or the both ends of the forge?  A. You need at least a 4" to 4 1/2" square opening in one end to let the forge be able to breathe.

Q. Do I need a regulator and ball valve both on my hook up for my forge.   A. Yes you need both, a regulator is needed to control the operating pressure going to the burners.  A propane tank can have around a 125 psi, you need to be able to regulate it down to a range of 3 to 35 psi.   A regulator can not be used as a shut off valve, if you notice most propane regulators ratings do not go down to 0 psi.
  Q. I have heard of Kaowool, Cerablanket, and Inswool, but I have not heard of Durablanket.  Are all of these products the same?  A. These are all different names of ceramic blanket made by different manufactures, they all come in different thickness, temperature ratings and different densities.  You want to use the the 8# density with 2300 degrees temperature rating or greater. The Unifrax Corporation has manufactured Fiberfrax high temperature insulation products since 1942.

Q.  I am wanting to line the inside of my 10" pipe forge or propane can forge with 2 inches of ceramic blanket lining, should I use the 1 layer of the 2" or 2 layers of the 1"?   A. You should use two layers of the 1" ceramic blanket, because it will be easier to form to the shape inside of the forge.  The 2" is a lot harder to work with.  Plus if you tear up the inside layer of the ceramic blanket, you can replace it and not have to replace the outer layer, so this will be a lot cheaper when it comes time to reline the forge.  The 2" blanket can be used for larger forges and for making movable forge doors.

Q.  I’m new to propane equipment and fittings so I’m not sure how the burner pipe nipple is attached to the propane hose.  What fitting is required between the actual burner and the hose coming from the regulator?    A. You will need a 1/4" ball valve and a 1/4" x  1/8" threaded bushing, to go from the propane hose to the 1/8" nipple on the burner.

Q. I am thinking about building my own flare and welding a nut onto the end of a piece of 1/8" schedule 40 pipe to attach my Tweco tip too, do you think that this will work o.k.?    A.
One of the important things about any atmospheric burner is that you get the jet centered in the burner tube.  Any time you start adding and welding things on you run the risk of getting it off center and diminishing the burner performance.  The flare is also critical,  I have had a lot of people call and say that they can not get there burner to run right, and then find out that they made there own flare.  That they thought was close enough.  If you read on Ron Reil's web site he states the importance of the proper flare.  I am not saying this to try to get you to buy my products, but to save you some of the troubles that others have experienced in building them.

Q. What size forge could I run using a single 3/4" side arm burner?  A.  You could build a forge 10" in outside diameter with 2" of Durablanket insulation and 10 to 12 inches long with one side arm burner for general forge work.  The rule of thumb for side arm burners to forge volume is: (1) 3/4" side arm burner for every 350 cu/in of interior forge space if you are wanting to achieve forge welding temperatures. Note: these figures are for a properly insulated forge.  The following links are to a couple of online calculators that will let you figure the inside area of different size cylinders.     http://www.online-calculators.co.uk/volumetric/cylindervolume.php     or    

Q. How do I tune a Side Arm Burner?  A. To tune a Side Arm Burner you will need to remove it from the forge and work with it  open air.  I like to tune them when it is dark, because it is easier to see the flame and different colors.  The first thing you need to do is adjust the position of the Tweco tip inside of the reducing tee while the burner is lit, slowly move it back and forth until you achieved an smooth and even flame.  You will also hear the sound of the burner change as you move it also.  The other thing you need to do is tune the burner flare,  moving it slowly back and forth to achieve the best stable flame that will not flame out and will run at a pressure range of 3 to 35 psi.  You will probably end up with a nozzle exposure of somewhere between 1-1/4" and 1-1/2".  If you have trouble getting you burner to run right, some of the problems that I have seen are the hole that was drilled in the pipe plug was drilled off center or crooked causing the gas jet not to be in the center of the burner tube.  I have also seen metal shaving and Teflon tape inside of the contact tip, this will cause a very erratic flame.  Below is a picture of what your flame should look like when you are finished tuning it.

Picture of the burner flare with the burner running at a
        normal flame

Q. What is the normal operating pressure of the side arm burners?  A. The normal operating pressure of a 3/4" side arm burner using a .035 contact  for general forge work is 7 to 8 psi.  This is not set in stone this gives you a good starting point when setting your pressure, a lot depends on your forge size and design.

Q. What size drill bit do you use to drill the hole in the 1 1/4" pipe plug for the 1/8" x 4" nipple?  A. I use the letter Z size drill bit.

  Q. What is the purpose of the idle circuit?  A.  The idle circuit is used so that you can instantly drop your forge to a quiet idle when you are removing a piece from the forge, or tending to some other chore by simply turning off the ball valve in the idle circuit.   When you return to the forge and simply turn the ball valve on the idle circuit back on and instantly bring the forge back up to full heat. You will discover that the forge will not lose its operating temperature when in idle mode either.  You will need to adjust the needle valve to ensure a proper idle flame. 

Q. Is it really necessary to have a choke on your side arm burner?  A.  Having a choke on your burner will allow you to better achieve oxidizing, neutral, or reducing, flames as needed by simply adjusting the choke and the gas pressure.

Q.  I had always thought the burner should come in at an angle and the flame should vortex inside the forge to help prevent hot spots?  A.  I have always felt that you really only need to vortex the burner when you are running a blower driven gas forge and not on a atmospheric forge.   I feel that because you are pushing the heat through so fast with the blower that you need some time to let the heat disperse evenly in the forge body.  You do not have all that much flow with the atmospheric burners, so it seems to spread more evenly.   The forge also has the flat firebrick bottom, every forge that I have seen that had a flat bottom and a vortex burner the flame seamed to hit a flat spot and wants to shot out the front opening giving another hot spot or uneven heat.  I am sure that there are others that will disagree with this thinking, but these are the findings from my own personal experience with forges over the years.  

Q.  Do you use any pipe dope or pipe tape on your propane fittings and the threads on the mig contact threads when you are assembling them?  A.  Yes, I use
Loctite® QuickStix™ PST® 561™ Pipe Sealant.  The following URL  is a link to the Loctite product information page for the pipe sealant.  http://www.loctite.com/int_henkel/loctite_us/index.cfm?&pageid=19&layout=3

Q.  I fired up the forge with no problem it  put out a nice flame,  but then I went to fire it up again later on all I got was just a minimal flame (looked like a cooking flame)  with no pressure registering on the gauge.  As soon as I shut off flow to the burner the pressure would come right back up any ideas?  A.  It sounds like you are running a 20 # LP cylinder with an excess flow device , and that is what is causing you your problem.  When using a tank with an OPD valve with the excess flow device or check valve, it is better to light the forge, starting with all of the valves turned off.  Then turn the triangular hand wheel one complete (360 degree) then turn the forge on and light it up.  From here you can adjust slowly for a higher flame.   There are a couple of other things that can cause you to have similar problems, you need a full flow POL (tank fitting).  There are some that have an Excess Flow Valve built into them and there are others that have a fixed orifice, these will not work.  The other thing is to make sure that you have the proper LP regulator like the Fisher model number 67CH-743,  you can not use the regulators that they sell for gas grills and small appliances; they do not have the BTU ratings that you need.  After a forge is up and running and one of the burners starts to flutter, it may be so that the burner is sucking in exhaust fumes from the forge openings.

Q.  Is it true that gas forges put out a lot of ultraviolet light?  A. No, the only fuel gas that puts out an appreciable amount of ultraviolet light (UV) is hydrogen (unlike hydrocarbon fuels, straight hydrogen gas has no free carbon in the flame to "soak up UV and re-emit the radiant energy in other wave lengths). As to the incandescent interiors of forges, they put out a lot of infrared and visible light. With the single exception of hydrogen flames, you need about 6000 degrees or more to create UV. So, it is a serious concern from electrical arcs and incandescent lamps, but not from forges. (submitted by Michael Porter )

Q.  What is the best way to cut the Durablanket and the Duraboard materials?  A.  The Durablanket can be cut with a razor knife with no problem.   When I cut the opening for the burner to pass through the blanket, I use a small kitchen knife.   This allows you to cut the hole with the Durablanket inside the forge body, insuring you proper hole alignment.  The Duraboard can also be cut using a key hole saw, wood hand saw, or a jigsaw.  The Duraboard is easily cut into any shape you want using these methods.  Always be sure to wear proper respiration protection when working with these products.

Q.  I am in the process of building a gas forge and was wondering, would you suggest doors on both ends or one end being sealed with a "pass through" hole that can be closed?    A.  I feel that this would really be a matter of personal preference, a lot would depend on what kind of work you plan on doing with your forge.           A door in the back of the forge would be far more flexible in use than a back with just a pass through hole.

Q.  How do I properly light the gas forge?    A.  First make sure that your ball valve is shut off at the burner or burners, then fully open the valve on the propane tank.  Set your regulator from 5  to 7 psi.   You can either light a small piece of paper or use a lit hand held torch.   The piece of paper must be placed inside the forge and  then slowly open the ball valve on the burner.  If you chose the torch method , you will need to place the torch in front of the forge opening and slowly open the ball valve.    Be sure to keep your hands and arms away from the front of the forge to prevent getting burned.

Q. How is the Duraboard held in place in the doors of the forge?  A.  I have used the QF-180 to glue it into place and I have also have used 10-32  screws taped through the sides of the doors to hold it into place.
QWhich product is better when building a gas forge the Durablanket or the Duraboard?  A.  The Durablanket is better if you are building a round or oval shaped forge and the Duraboard is used when making square or rectangular shape forges, they have the different  thermal properties, 2 layers of 1" 8# density Durablanket is about the same as 1"thick 18# density Duraboard.  I have used both products on forge doors with no problems.

Q.  Can I run the side arm burners off of natural gas instead of propane?  A.  I have never done it but I have been told that you would need to double the orifice size for natural gas.  The big problem with running the burners on natural gas is that you will need at least 15 psi of natural gas and most residential gas services only have inches of water column.  If you have a commercial gas service you should be alright.

Q.  I have never set up anything like this before can you tell me how 
the parts go from the propane tank to the burner?   A. 
Here is how all the fittings go starting at the tank, the POL screws into the regulator inlet, the hose screws into the regulator outlet, then the ball valve screws into the other end of the hose, then the 1/4 x1/8 bushing screws into the other side of the ball valve, and then the 1/8" nipple of the side arm burner screws into the bushing.  There is a gauge port in the side of the regulator that you remove for the gauge.

Q. Do I coat the inside of the forge body with the Plistix 900F coating  before I install the Durablanket or do I just coat the Durablanket once it is inside of the forge?  
A. You just need to put the Plistix coating on the inside surface of the Durablanket once you have the forge lined. You do not need to coat the forge body or were the burner flares go through. You just want the inside of the forge coated to help protect the Durablanket and help reflect the heat.

Q.  I am building a  10"round body forge and insulating it with 1" Durablanket, what do I need to use to hold the Durablanket in place ?  A.  You do not need anything to hold the Durablanket in place it is rigid enough to hold itself in place.  Just make sure that you have a tight fit when installing the blanket.
Q.  On a multiple burner atmospheric gas forge using side arm burners what do you recommend  the spacing to be between the burners ?  A.  I recommend the burners to be 3 1/2" to 4"  on center and no more, this will insure that you get an even heat on your pieces of metal that you are heating.

Q.  How long will a gas forge with one side arm burner run on a 20# propane cylinder ?   A. A 20# cylinder will last for about 7 or 8 hours when running around 7 or 8 psi.  If you have problems with the propane tank freezing up you might want to consider manifolding two 20# tanks together are getting a larger cylinder.  There is a picture of this set up on my burner parts page.  Note: 
Blue Rhino and others that exchange 20# cylinders clearly state on the label that the net weight is 17#, however these are 20# tanks and they can be safely filled to this capacity or very close to it at a propane dealer.
Do I need to place some kind of spacers under my fire bricks or do I just lay them on top Durablanket?  A.  You can just lay the firebricks on top of the Durablanket it will compress the Durablanket a little but it will be fine.

Q.  I am wanting to build a large gas forge for pulling out large scrolls, I am thinking about building it four foot long.  What do you think about this idea?  A.  I would suggest building (2) two foot long forges that you could butt together instead of building one four foot long.  This will give you a lot more flexibility, if you do not need the whole four foot you can separate it and just use one of them.

Q.  Can I get by using just one inch of  Durablanket for my gas forge insulation ?  A.  No, I would say that you need at least two inches of the Durablanket for a well insulated forge.

Q.  What is the best gas forge design?  A.  This seems to be one of the most asked questions that I get anymore.  I do not think that there is a perfect design that meets everyone needs.   I guess it really depends on what kind of work you are wanting to do with the forge.   One of the main things is that the forge design works for the type of work that you are going to do with it.    I have seen commercially built forges and homebuilt forges that look nice but are really limited to what work you can do with them because they have a small fixed opening in the front and the rear of the forges that restrict the size of the work that you can put in the forge.   Both the simple gas forge design and the square body forge design on my web site allow you to use the whole interior of the forge.   Because on the square body you can simply open the front door or on the simple gas forge you can simply reconfigure the bricks to have a larger front opening.  The simple gas forge is cheaper and easier to build due to the materials used.    I realize that the insulated firebricks are not the greatest  ends to have on a forge, but you are able to configure them to the size needed for the work that you are doing.   The square body forge, with its open front and back doors that you can remove or raise to let stock pass through is a good all around design that seems to work well.

Q.   How far should the burner flares stick into the forge?  A.  Type 304/304L stainless steel is a chromium-nickel material that offers very good corrosion resistance up to 1600 °F, the temperatures inside a forge body will far exceed these temperatures ratings so you must keep the burner flares out of the interior of the forge.   When installing burner assembly in the forge, the flare should not extend down into the forge chamber, it should be up inside the Durablanket about a 1" to a 1 1/2" to help protect the flare from the high heat in the forge chamber.

Q.  I have a forge body that is 12" in diameter and 24" long, how do I figure out how much ceramic blanket I will need to line it with two layers?  A.  You take the forge diameter times pi 3.14 and this will give you the length of the first layer (12 x 3.14 = 37.68") and then subtract two inches from the diameter to account for the first layer and multiply that diameter times pi 3.14 (10 x 3.14 = 31.4").  So you would roughly need 6 running feet of 24" ceramic blanket to line a forge with those dimensions.

Q.  I recently purchased a single burner connection kit from you and I am not sure how it goes together.   A.   Click here for Single Burner connection kit assembly instructions.

Q.  I recently saw a hand held torch outfit (weed burner) at Harbor Freight will this work as the burner in a gas forge  ?  A.  No, these weed burners were not designed to be put into a forge and will not work in place of a properly designed forge burner.

Q. Is there any benefit in having a heavy wall forge body over a thin body forge like the 5 gallon bucket forge body?  A.  There is no benefit in a heavy forge body, that is why I recommend using a bucket for the forge body

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Copyright ©2000-2021 Larry Zoeller

Last Revision 01/11/21

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