Weld Procedure For 5CR To 317L???

[BlackwellS]

Gents,
I have a reduced crude vacuum transfer line (700F) subject to localized napthenic acid attack. Metallurgy on the line is 5CR (A335 GR P5). One of our options is to upgrade a number of small-bore connections (thermowells, vents, etc.) and L.R. ells to 317L. Could someone provide general guidance on welding 5CR to 317L? Is this dissimilar weld even possible? Is there a single rod available, or would we need to lay down intermediate passes of varying weld metal? I assume PWHT would also be required.

Also, could anyone recommend a good welding "handbook," or guide? Maybe from the WRC or AWS that may assist? Thanks!

 

[metengr]

In reading your post, it sounds a bit confusing. You mention that the 5Cr-1Mo transfer line is suffering from corrosion. Yet, you want to upgrade the connections to this line using an austenitic stainless steel.

Do you intend to repair or replace the corroded 5Cr line or simply replace the connections because they are susceptible to local crevice corrosion?

Yes, the 5Cr-1Mo can be joined to an austenitic stainless steel using either a 309 or nickel-based electrode.

 

[BlackwellS]

First, thanks for the info! FYI, we have a corrosion inhibitor (chem injection) to mitigate the issue with NAC on the straight-runs; but this type of corrosion most difficult to control in areas of two-phased flow, directional changes and more turbulent locations adjacent to welds (e.g ells and nozzles). We do not intend to replace the entire line at this time.

The most effective way to combat this problem is by using metals with higher moly content to resist the organic acid of higher TAN crudes; hence, the idea of using 317L.

 

[metengr]

Ok. I would use a nickel-based electrode (like ERNiCrMo-10) for the dissimilar metal weld. You will need to preheat and PWHT if welding directly to the 5Cr-1Mo material.