Welding of ASTM A197 Threaded fitting to carbon steel pipe

[Everynameistaken]

Posted in the metals section but not too many responses!


Hello,

I am a structural and I need to weld a threaded weldlette to a 36" pipe to use as a float, so I can fill the pipe with expanding foam and then thread in a cap to seal up the access port.

My question is:

I am specifying pretty generic low grade pipe, there is almost no pressure load on the pipe as its just the static water pressure so 1m of water head. The pipe is carbon steel to ASTM A252 or similar with 240 Map yield. Can I weld ASTM A197 Cupola Malleable Iron to the carbon steel?

If so, is there anything special about the weld?

If not, what is the type of threaded weldolette that I should use instead?

Thanks Very Much

 

[Ron]

Yes, you can weld a weldolet fitting to this pipe. I would use E7018 electrodes rather than an E6011 or E6013 to keep the penetration reasonable and not dig too deeply into the pipe.



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[JStephen]

I wouldn't think welding parts would be made with malleable iron, more commonly see A105 or A181 forged fittings for welding.

 

[dhengr]

Everynameistaken:
Put several of those weldlettes on the large piece of pipe. When that foam starts expanding it needs someplace to vent and expand/overflow or you can develop considerable pressure. Tape the threads up before you start or they’re a mess to clean up too.

 

[Everynameistaken]

Thank you everyone!

Our plan is to fill with billet foam first and only use some expanding foam where required.

Good point on the expansion pressure, we will make sure there is an air release.

The ASTM A197 is malleable iron and requested by our fabricator. The pipe itself has almost no load on it just did not want to crack the weldolte.

 

[Dhurjati Sen]

Dear Everynameistaken,

E7018 will not work. Check my reply in the Metals section.

Regards.

DHURJATI SEN
Kolkata, India

 

[LittleInch]

Really don't understand why the fabricator is requesting this type of fitting or indeed why the tail is wagging the dog here.

You're the engineer - Specify materials which are compatible with each other for welding.

If this is a float, why not just seal the ends and leave it full of air?

Or is the idea that it is just a pipe?

Can't you use PE pipe instead?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Everynameistaken]

we Want to use steel for the durability and much easier to connect too.

Foam fill is typical for floats as an insurance policy so the do not spring a leak and sink.

I agree we should be getting the right product but it was a request from the contractor to the owner and we need to outlay the potential risk or issues with using such a product. If it can be done correctly and that fabricator has experience in doing it then we do not see why it can’t be done.
The issue was, can it actually be done? And we were not sure of that. From reading above and lots of other places, our understanding is yes it can be done provided the right process is in place to do it correctly. Might be easier to use a forged steel and we have suggested that alternate as well.

am I missing something?

 

[mk3223]

As replied on your post on the other forum, you shouldn't endorse the Contractor's idea which may become your responsibility if accepted the proposal.
Too often an Engineer to be a typically problem-solving approach, you may think there is "always" a right procedure available for everything. However, the reality is that sometimes an "easier" solution can be the right solution as well, IMO.