Best steel for boilers?

PolarLight · Post by **PolarLight** » Mon. Jul. 15, 2019 11:06 am

I couldn't find any info on best steel for boilers here.
I want to weld another boiler for my farm, and the guy who sales steel asked me about grade. I have no idea, tried search Google, can't get any info.
Some people say steel 08х13 (AISI 409) is the best for boiler manufacturing. Others say don't buy it because it too hard to weld. As far as I understood I need corrosion resistant steel that can stand heat and pressure. But it also can be welded easily. I am going to weld it in my garage with MiG welder.

PolarLight · Post by **PolarLight** » Mon. Jul. 15, 2019 11:36 am

Found some info on
https://www.azom.com/article.aspx?ArticleID=969

Steel 3CR12 -easy to weld and good corrosion resistance. Heavy sections are more easily available then 409.

tsb · Post by **tsb** » Mon. Jul. 15, 2019 11:52 am

Use regular old A-36 steel and steel tank flanges. If you have an industrial duty mig and are and excellent welder you'll be fine. If not, you'll just make a sprinkler system. With 409 there would be no hope. Heat transfer with A-36 is better that any stainless grade. The system must be closed and oxygen free to survive more than a few years.
I suggest you get a better steel salesman.
Good luck with the project.

PolarLight · Post by **PolarLight** » Mon. Jul. 15, 2019 12:19 pm

Thanks tab, I will look for A-36 steel, and try to not make a sprlinkler system...

.
What thinkness do you recommend?
0.1575" would be enough? Or, I need 0.2"?

tsb · Post by **tsb** » Mon. Jul. 15, 2019 12:39 pm

The thickness will be determined by your design. 10 ga is probably the minimum. 3/16 to 1/4 if you have a lot of flat areas under pressure. When you pressure test, bring it up slowly using water not air. If you use just air, not more than 15-20 lbs. tops.
Look through this post
Sounded Easy at First

PolarLight · Post by **PolarLight** » Mon. Jul. 15, 2019 2:44 pm

Just checked your work. What a amazing job you done!
However, I keep very different design in my mind. Firstly, I need boiler that works on both wood chips and anthracite. Secondary, I am planning to heat 3 building with total area 6500sq.f .
So, instead of welding cheat exchanger with outer pipes, as you did I am planning to do the opposite, let gases going into pipes,not the water.
I think keeping more water will give me more flexibility, or forgiveness in case something wrong with controller.
Another aspect, would be more easy to clean exchanger. Here how my exchanger going to look like.

Post by **coaledsweat** » Mon. Jul. 15, 2019 5:08 pm

PolarLight wrote: ↑
Mon. Jul. 15, 2019 2:44 pm
Firstly, I need boiler that works on both wood chips and anthracite.

That's going to be a serious problem that I doubt you will be able to overcome.

PolarLight · Post by **PolarLight** » Mon. Jul. 15, 2019 5:40 pm

Yes you are right. I already thought about it.
Already ordered custom made 6" auger with a big retort burner pot at the end. Setting for anthracite and wood chips will be very different. Less air and more auger speed for woodchips. Hope will find it experimentally. I have a wood mill just 5 miles away, they are offering free wood shavings. That is a game changer. I am planning to build a hooper with wheels, kinda trailer that I can hook up to my pickup and drive to the mill, then I will hook it up back to the boiler.
However, I don't know yet how to overcome problem with chavings, which are come in different sizes, unlike chips. I Know that some advanced woodchip augers have sorta a chamber for choping chips, and making them equal. Too hard to copy this technology.

PolarLight · Post by **PolarLight** » Mon. Jul. 15, 2019 6:05 pm

I am a former scientist, always looking for problems to solve. Well, sometimes problems turns to be just troubles.

lsayre · Post by **lsayre** » Mon. Jul. 15, 2019 7:14 pm

ASME SA 516 Grade 70 steel.

PolarLight · Post by **PolarLight** » Tue. Jul. 16, 2019 12:06 am

Thanks Isayre.

McGiever · Post by **McGiever** » Tue. Jul. 16, 2019 2:05 am

Corrosion is not an issue as a proper boiler will operate with O2 being devoid of water within...

McGiever · Post by **McGiever** » Tue. Jul. 16, 2019 2:07 am

PolarLight wrote: ↑
Mon. Jul. 15, 2019 5:40 pm
Yes you are right. I already thought about it.
Already ordered custom made 6" auger with a big retort burner pot at the end. Setting for anthracite and wood chips will be very different. Less air and more auger speed for woodchips. Hope will find it experimentally. I have a wood mill just 5 miles away, they are offering free wood shavings. That is a game changer. I am planning to build a hooper with wheels, kinda trailer that I can hook up to my pickup and drive to the mill, then I will hook it up back to the boiler.
However, I don't know yet how to overcome problem with chavings, which are come in different sizes, unlike chips. I Know that some advanced woodchip augers have sorta a chamber for choping chips, and making them equal. Too hard to copy this technology.

Change burners for changed fuels...the same vessel won't know the difference.

Best steel for boilers?

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