Sleeve Weld - OLD TO NEW Aluminium

[RUSS_YULO]

Evening folks

Im after some advice, our welding contractor is replacing some aluminium pipework and will weld old to new.
We do not know the old Aluminium composition so the contractor has proposed rather than a standard butt weld (old to new) they will have an aluminium sleeve over the top with fillet welds.

Is there any advice or risk to using the sleeve weld?
Also what is the risk with the old unknown grade of Aluminium?

 

[Brad93]

That won't be needed if the guy welding it knows what he is doing.

Sounds like he doesn't.

 

[Brad93]

Risk. Is it pressure pipework? What liquids is it carrying?
If it's pressure the material needs to be certified to meet WPS / any sort of insurance.

Needs to be prepped & TIG welded properly. That doesn't help you with filler choice though.

 

[hotrodder]

As said knowing what sort of pressures (if any) it's dealing with is kinda important along with service temps and what sort of fluids are involved, for example sleeving could result in crevice corrosion becoming an issue

Is it schedule pipe or tube? Measuring it should answer that and in turn narrow down the most likely flavours of ally... while either could be a variety of different alloys a 6xxx series is waaaaaaaay more common for tube and if buying sch pipe then 5083 is the most commonly available suspect. Depending what the pipework is for that might be good enough or not even close

 

[ronan]

Can't be too high a pressure or they would have used steel surely ? Even thin walled stuff like dairy tube would be stronger than relatively heavy walled aluminium ? Are the tubes part of a cooling system ?

 

[hotrodder]

http://www.tubeweb.com/Non-Ferrous-Tube/theoretical-bursting-collapsing-pressures-for-pipes.html
Double the wall thickness and ally will still be cheaper & lighter than stainless, triple it and there won't be much in it weight wise but it'd probably cost more? Obviously there's a lot more to it but ally can sometimes make lots of sense

 

[RUSS_YULO]

Pipework is under vacuum and carrying a gas.
Service temperature is around 25 degrees.
New pipe is 5754 old Pipe is unknown, sleeve is 5754
New and Old Pipework is DN65 3mm wall, sleeve has an ID of 71mm, OD of 85mm (7mm wall).

No RT of the Sleeve Fillet Welds, but Helium Leak Test and visual to be carried out.
Gap shot may be taken.
Questions from client regarding concerns with porosity,contamination, penetration, undercutting and cracking.

 

[Brad93]

There is always porosity with aluminium, the amount permitted depends on WPS. If prep is correct contamination will be minimal. Cracking and undercut is down to the operator and the use of correct filler for the parent metal. I'm not familiar with 5754 but you can look that up on esab or similar filler metal chart.

 

[knighty]

what's access like ?

easier to sleeve it than cut the ends of the pipe to match up if access is tricky ?

and what's the condition of the old pipe like ? easier to sleeve it if it's a bit rough ?

either way, there's no real down side to sleeving it that I can think of ?

 

[Brad93]

what's access like ?

easier to sleeve it than cut the ends of the pipe to match up if access is tricky ?

and what's the condition of the old pipe like ? easier to sleeve it if it's a bit rough ?

either way, there's no real down side to sleeving it that I can think of ?

I can. If you sleeve it your increasing the likelyhood of the leak down test failing because you've got two welds, fillet welds as well, rather than one Multipass butt weld.
You're also exposing the clean insides of the pipe to the corroded/oxidised exterior of the pipe.

 

[Brad93]

Tbh i think you should be consulting with a specialist rather than an internet forum. There are some very knowledgeable guys on here, but if it all goes wrong the only response you have is so-and-so on MIG welding forum said.

 

[RUSS_YULO]

One final question, we have a meeting with design specialist next week but Is there any benefit Radiographing or Dye Pen of the Fillet Welds?
Previously no FW have been radiographed.

 

[Brad93]

One final question, we have a meeting with design specialist next week but Is there any benefit Radiographing or Dye Pen of the Fillet Welds?
Previously no FW have been radiographed.

I'd definitely be doing some NDT if it's a critical system. Like you say you will be leak down testing with helium but that doesn't let you know if there is a defect in the weld that hasn't come to light yet. Obviously you've got options, dye pen, ultrasound, x-ray. Again depends how critical.

 

[Chris Stevens]

Im after some advice, our welding contractor is replacing some aluminium pipework and will weld old to new.
We do not know the old Aluminium composition so the contractor has proposed rather than a standard butt weld (old to new) they will have an aluminium sleeve over the top with fillet welds.

Is there any advice or risk to using the sleeve weld?
Also what is the risk with the old unknown grade of Aluminium?

View attachment 92238[/QUOTE]

If the consequences of problems are likely to be serious, would it be worth while consulting a qualified welding specialist rather than asking questions on here?

 

[Pete.]

Thread the sleeve and the old pipe, weld sleeve to new pipe, screw together.

 

[Richard.]

Pete if it's containing gas it's better off a welded joint.

 

[Brad93]

Im after some advice, our welding contractor is replacing some aluminium pipework and will weld old to new.
We do not know the old Aluminium composition so the contractor has proposed rather than a standard butt weld (old to new) they will have an aluminium sleeve over the top with fillet welds.

Is there any advice or risk to using the sleeve weld?
Also what is the risk with the old unknown grade of Aluminium?

View attachment 92238

If the consequences of problems are likely to be serious, would it be worth while consulting a qualified welding specialist rather than asking questions on here?[/QUOTE]

Exactly my thinking Chris

 

[Brad93]

Thread the sleeve and the old pipe, weld sleeve to new pipe, screw together.

As Richard says, are there any retro fit threading methods that will pass Helium leak down? I doubt it.

 

[WorkshopChris]

New pipe is 5754 old Pipe is unknown, sleeve is 5754

I am struggling to see how this helps as both the new pipe and sleeve are 5754 so why use a sleeve.
When you 1st said about the sleeve i imagined this would allow a different alloy to be used to possibly match the old.

 

[Chris Stevens]

If the consequences of problems are likely to be serious, would it be worth while consulting a qualified welding specialist rather than asking questions on here?

Exactly my thinking Chris[/QUOTE]



This type of question is really for someone with the appropriate hands on skills, who has is able to inspect the job personally, and not really the type of thing that can be answered on a net forum.