WELD CLADDED MATERIAL WITH NORMAL CARBON STEEL

[marcello1983]

Dear all, good night to everybody,
we have a case downstream christmas tree for oil production 8" 2500 rating where is required 10D of cladded pipe for chemical corrosion inhibitor injection.
After 10D of cladded material ( LTCS + 3 mm of ALLOY ) is request to change to Carbon steel 2500rating 8".
The question is : it is possible to weld cladded matarial with carbon steel material?
Which is the code that instruct how to weld this two material? which is the process?
There is some process to follow in order to weld the 2 material?

Since a couple of flange is not permitted I need to found a solution how to weld the 2 material.

Client have request 10 D after cladded material before the first welding point on carbon steel due to GALVANIC corrosion.
( but in my opinion is not real since we have carbon steel also after the cladded portion )
But not every place is permitted due to layout constrain.

In my mind I have this case :
1)Remove cladded material from cladded piping is not permitted since the remaining tickness is not design for design pressure.
2)Add some 200 mm of cladded material in carbon steel piping spool and weld with incoloy material
3)make a spool half cladded and half not from clad vendor.

Thanks a lot for the cooperation.
Best Regards

 

[metengr]

marcello1983

it is possible to weld cladded matarial with carbon steel material?
Which is the code that instruct how to weld this two material? which is the process?
There is some process to follow in order to weld the 2 material?

1. Yes, it is possible to join dissimilar materials - clad pipe to carbon steel pipe.
2. What is the code of construction regarding design and fabrication? This will determine what you need to do in terms of generating a welding procedure, qualification of the welding procedure, nondestructive testing, etc.

 

[weldstan]

I would recommend making the but weld to the clad pipe with 309LMo filler if the clad is 316 0r similar. If the clsd is a nickel-Crome Moly base alloy, use a filler metal matching to the clad alloy.

 

[EdStainless]

You are right that the correct method is to strip the clad and then weld CS to CS.
You say that the CS backing by it self does not provide adequate pressure rating? Are you sure? This would be unusual.
I would favor option #3. The properties of the mixed metallurgy welds will be somewhat irregular and may pose problems.
Of course welding clad to clad is no walk in the park either.

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P.E. Metallurgy, Plymouth Tube

 

[metengr]

In some cases cladding can or is used as part of the pressure retaining boundary, for example clad vessel construction. If the cladding is stronger than the base material you can't take credit for the higher strength.

In your situation, I favor making a dissimilar metal butt weld between the clad and carbon steel using Inconel filler metal or matching the clad composition.

 

[SJones]

If the cladding is being applied by weld overlay, simply stop the weld overlay before the welding end of the spool and complete fabrication with a carbon steel - carbon steel pipe girth weld. The 10D criterion for CRA length is a rule of thumb to allow inhibitor dispersion from the injection point and achievement of maximum protection. Provided that the end user has tested, selected and deployed the inhibitor to account for the interface between the CRA and the carbon steel, enhancement of corrosion on the carbon steel should not be an issue.

See, for example, the following:

NACE Corrosion 2009, Papers 09274 and 09566
NACE Corrosion 2010, Paper 10333
NACE Corrosion 2011, Paper 11270

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.