welding boiler

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squandt
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welding boiler

Post by squandt » Sun Sep 09, 2018 11:13 pm

Hello to all, I have a question about MIG welding a boiler. I have read that you should not use a MIG welder to weld your boiler. Why is this? As I have seen a boiler welded with a Mig welder for use in the food canning industry. the boiler working psi was 350 lbs. It was gas fired and ran 24/7 at the Hunts plant in Stockon California. Second part of my queston,when you put stays in the fire box/ wrapper sheet, do they follow the radius or go stright?
stay on the shine side of the rail

Harold_V
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Re: welding boiler

Post by Harold_V » Mon Sep 10, 2018 1:15 am

I can't address code today, but there was a time when there were no acceptable procedures for welding boilers with MIG. Perhaps Marty Knox will chime in, as he's a maker of boilers.

I asked my instructor about that when I was taking a welding class, and he demonstrated one reason why. While he had to manipulate the settings, he managed to lay down a weld that looked pretty decent, but could be knocked off with a hammer. There was no penetration.

The rod used when stick welding may require skill ( and it does), but it's pretty hard to not get penetration. Root passes are often made with 6010, with cover passes of 7018. Both tend to penetrate well, even in the hands of a guy like me (I am not a weldor).

H
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Bill Shields
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Re: welding boiler

Post by Bill Shields » Mon Sep 10, 2018 8:00 am

It is my understanding that there are now MIG procedures for code welding that requires very specific rod and procedures and certifications.

Never seen it done - but that does not mean that it cannot be done.

southwestern737
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Re: welding boiler

Post by southwestern737 » Mon Sep 10, 2018 8:11 am

There are acceptable procedures for MIG welding code boilers, I can’t remember all the specifics but it involves using flux core filler wire and shielding gas (double shield), it is not your everyday flux core wire it is a special wire specifically made for double shielding.
Brent

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Chris Hollands
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Re: welding boiler

Post by Chris Hollands » Mon Sep 10, 2018 10:10 am

The Australian model boiler code accepts Mig welding as my Challenger boiler is partly mig and Tig ,and that is a tough code .

Cant remember now what material was used to meet the code , someone will know from OZ or NZ .

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Marty_Knox
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Re: welding boiler

Post by Marty_Knox » Mon Sep 10, 2018 10:55 am

The first step in welding a boiler should be to develop a welding procedure. This spells out the joint design, the base metal, the filler metals, the welding process, the electrical parameters, and if pre or post-weld heat treatment is required. Once you have a procedure, you then qualify to that procedure.
I have never done or seen one for MIG welding on a boiler. But I had my welding training in 1981, and really haven't kept up on the latest technology.

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Chris Hollands
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Re: welding boiler

Post by Chris Hollands » Mon Sep 10, 2018 11:15 am

As Marty states , my boiler was done to a procedure and certified welder with those qualifications at the time .

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gwrdriver
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Re: welding boiler

Post by gwrdriver » Mon Sep 10, 2018 12:19 pm

To answer the second part of your question . . . ideally stays should be perpendicular to flat surfaces and co-radial to curved surfaces, and also symmetrical. That is, identical on both sides of the firebox. That's the ideal, but things don't always work out that way. You can see in the illustrations where a number of stays are fudged a bit to achieve a best average location, for instance having a co-radial engagement on one end and skewed on the other.

Make them perpendicular or co-radial where you can, and then do what you must (without being extreme) to adequately and evenly support the shells.
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david griner
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Re: welding boiler

Post by david griner » Mon Sep 10, 2018 3:17 pm

As credentials: Was an ASME Authorized Inspector for more than 23 years............................still participating in the work.

ASME allows ANY type of welding process to be used in constructing a boiler or vessel !! HOWEVER !! each process used (SMAW, GTAW,GMAW etc.) must, I repeat, must have a proper Welding Procedure Specification (WPS) , accompanied by a Procedure Qualification Record (PQR), in addition to a Welder Performance Qualification Record (WPQ)...............without any one of these documents the associated welding is unacceptable......................period!!
That's how the "Code" views this situation.
GMAW, for reasons noted above is quite susceptible to lack of fusion...........................therefore, unless there is a proven WPS+PQR and Skill level WPQ available, it is strongly recommended NOT to use this process for your boiler.
Respectfully,
Dave Griner

Harold_V
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Re: welding boiler

Post by Harold_V » Mon Sep 10, 2018 3:30 pm

I was horrified when an individual who used to be a member of the Southern Oregon Live Steamers told me that he had MIG welded the boiler (his) for a UP Big Boy. The engine was finished and running some time later, and ran without issue. Goes to show it can be done, but it does offer some risk, just as any procedure does if not done properly.

The builder in question passed on many years ago. I have no idea where the engine is now.

H
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ALCOSTEAM
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Re: welding boiler

Post by ALCOSTEAM » Tue Sep 11, 2018 5:48 am

Possibly the easiest to understand reasoning against mig for boiler welding is its lack of penetration. On boiler welding your root pass if you look at the underside of the weld should look just about identical to a finish pass on the top side. Stick and Tig welding are the only viable way most have of achieving this.
I have seen mig used in finish pass welds on pressure vessels including a large boiler. Submerged arc is commonly used in commercially built pressure vessels and its an adaptation of mig welding (or vice versa) where a shielding flux is laid down ahead of the weld. As you can envision this is used in a machine controlled welding setup.

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10KPete
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Re: welding boiler

Post by 10KPete » Tue Sep 11, 2018 4:33 pm

david griner wrote:
Mon Sep 10, 2018 3:17 pm
As credentials: Was an ASME Authorized Inspector for more than 23 years............................still participating in the work.

ASME allows ANY type of welding process to be used in constructing a boiler or vessel !! HOWEVER !! each process used (SMAW, GTAW,GMAW etc.) must, I repeat, must have a proper Welding Procedure Specification (WPS) , accompanied by a Procedure Qualification Record (PQR), in addition to a Welder Performance Qualification Record (WPQ)...............without any one of these documents the associated welding is unacceptable......................period!!
That's how the "Code" views this situation.
GMAW, for reasons noted above is quite susceptible to lack of fusion...........................therefore, unless there is a proven WPS+PQR and Skill level WPQ available, it is strongly recommended NOT to use this process for your boiler.
Respectfully,
Dave Griner
Yep, did a whole bunch of that back in the '70s and '80s. Had a handfull of PQRs and WPQRs for MIG, TIG and stick. Last I did was about 1982 and I'll bet things have changed since then! The biggest problem with TIG is having enough heat at the start of the weld. Without pre-heating the first few inches the risk of cold lap is great. Some joints will allow use of a start tab a few inches long to get started, as well as a runout tab. Once the weld is hot the puddle will fuse nicely. Circular joints usually require grinding out the first few inches.

I don't recommend MIG unless the specific WPS and PQR are followed...

Pete
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