CDU Overhead Piping - Materials of Construction Best Practices 1

[Guest102023]

We have planned all the necessary corrections for diameter, injection, etc.
At the moment we view Hastelloy C276 as 'industry best practice'. Can anyone validate that with refinery experience?
Is Inconel 625 an acceptable alternative, given that it is easier to work with roll-bonded I-625?
I would also like to get opinions on roll-bonded vs. solid vs. weld clad.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[DBreyer]

Hey,

I think the best alloy strongly depends on the corrosivity in your system.
We have 625 in one CDU and alloy 59 in another one. Both perform quite good in there respective conditions. T
he alloy 59 was used in a system where strong salt formation and relatively sour media are present.
In my experience there is no difference in performence btw. roll-bonded and weld clad alloys in CDUs.
Since the hydrogen partial pressure is no issue here disbonding won't be a problem.
Of course you have to be carefull with the dillution of the base metal and need sufficient passes when you weld in order to reach the specification limits of your alloy (especially Fe-Content). Solid CRA we only use for small bore piping or small nozzles.

Daniel Breyer
Inspection Engineer

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