gas forge newbie

[kcza]

Hello,

First post ever, hopefully not the last.

I just built a gas forge, and coming from a coke forge and being used to its simplicity, I probably didn't think everything through as i should, so im here, in need of advice.

I used STV-2 fire bricks, not sure whether this is a brand or standard, but apparently its rated for 2800f. Bricks are almost 2 1/2" thick. I couldn't drill the entry hole myself so i asked my neightbour to do it, but unfortunately the hole he drilled was 1/2" too big, so i had to insert a metal pipe in order to fix the burner in place. The pipe is sealed from the top with furnace cement, but i think its rating is not high enough for the application. Inside the pipe and around the burner i packed refractory wool to prevent backfires.  

The burner is from Devil Forge

Today was my first time using it, and after about an hour and a half of work i tried to touch the burner to feel how hot it was getting... i was unpleasantly surprised to find out it was too hot to touch, by the valve, not on the burner body, the valve.

My humble opinion is that, the pipe sleeve is conducting internal heat up the burner.

Im not scared of criticism, so dont hold back.

Zak

 

*measurements and temperatures were converted from metric to imperial since im from eu

[Buzzkill]

First, the bad news: You used a type of fire brick that is suitable for fireplaces, but is not good for gas forges.  The brick you used is hard and dense, and it can withstand the temperatures.  However, it is not insulating to any appreciable degree which makes it a huge heat sink.  Even if your burner can heat the forge, it will take much longer and burn significantly more fuel to bring it up to temperature.   What you want is insulating fire brick (IFB).  These bricks are much lighter and softer.  They can easily be cut with a dull hacksaw blade.  However, they are much more expensive and more fragile than hard fire bricks and they can develop cracks from repeated thermal cycle.

The good news is you can probably use the frame you built and replace the hard fire bricks with insulating firebricks.

I have no personal experience with Devil Forge burners, but I agree that the burner should not be too hot to touch where you indicated while in use.  Once you shut the burner down, heat will rise up around and through the burner, heating everything in its path.

You do have a fairly large gap between the mixing tube of your burner and the mounting pipe.  If you have any ceramic fiber blanket pieces you could stuff the spaces with the blanket to see if that solves your issue.

We have a quite a few threads on here regarding gas forge construction.  It would be worthwhile to spend a few hours reading through some of these to get a good handle on the topic.  Here's a couple to get you started:

https://www.iforgeiron.com/topic/47439-forges-101/

 

https://www.iforgeiron.com/topic/61288-my-consolidated-notes-for-new-forge-builders/

 

[Irondragon Forge ClayWorks]

Welcome aboard... If you put your location in your profile, you may be surprised how many members are near enough to give hands on help.

Does the burner get that hot while it is running, or only after shutting it off? I don't think the pipe port is the problem. I have a much larger gap in my forge port and the burner stays cool enough to touch while it is running, but gets pretty warm when shut down, unless I close the air choke to prevent the chimney effect. How far does the port and burner extend into the chamber?

[kcza]

1 hour ago, Buzzkill said:

First, the bad news: You used a type of fire brick that is suitable for fireplaces, but is not good for gas forges.  The brick you used is hard and dense, and it can withstand the temperatures.  However, it is not insulating to any appreciable degree which makes it a huge heat sink.  Even if your burner can heat the forge, it will take much longer and burn significantly more fuel to bring it up to temperature.   What you want is insulating fire brick (IFB).  These bricks are much lighter and softer.  They can easily be cut with a dull hacksaw blade.  However, they are much more expensive and more fragile than hard fire bricks and they can develop cracks from repeated thermal cycle.

The good news is you can probably use the frame you built and replace the hard fire bricks with insulating firebricks.

 

 

Well that sucks, the company that sold me the bricks was aware of what im going to build, and they ensured me its fine. Thanks for making this clear and providing links for research.

55 minutes ago, Irondragon ForgeClay Works said:

Does the burner get that hot while it is running, or only after shutting it off? I don't think the pipe port is the problem. I have a much larger gap in my forge port and the burner stays cool enough to touch while it is running, but gets pretty warm when shut down, unless I close the air choke to prevent the chimney effect. How far does the port and burner extend into the chamber?

It was hot while running. I did try and touch it a few times after i turned it off, but it was so hot i couldnt tell the difference anyway.

The port and burner both sit flush with the chamber ceiling. 

Also, I forgot to mention the burner was running at 0.14MPa (roughly 20 psi) for an unknown amount of time because the pressure rised sometime during use. The pressure I set was 0.1 MPa (14psi).

Not sure if it matters, and if my calculations are correct, the chamber is 264 cubic inches in volume.

 

Zak

[ThomasPowers]

Most commercial refractory dealers are used to working with commercial users where a hard firebrick might be good for a high production environment. They may NOT be all that aware of how hobby blacksmiths build and use their forges where efficiency plays a larger role.

Hard firebrick makes for a very nice pad around your forge to be able to set hot metal on. (I use an old real soapstone lab bench top, for one of my forges)

[Mikey98118]

5 hours ago, kcza said:

My humble opinion is that, the pipe sleeve is conducting internal heat up the burner.

Yes, but that loss is insubstantial. You're losing a lot more heat up the opening between burner port and mixing tube. You appear to have use a section on pipe instead of a reducer, and it is 'nt a large enough diameter, either.