MR0175 & Cladding

[Corgas]

According to this spec : "Unless the user can demonstrate and document the likely long-term in-service integrity of the cladding as a protective layer, the base material, after application of the cladding, shall comply with NACE MR 0175"

Question : If we do a proper QA/QC during cladding installation, is that enough to satisfy above requirement? In this particular application cladding will be 316L and base material SA-516.

 

[gr2vessels]

It all depends on application, on the rigidity (or flexibility) of the cladding specification, on the design of the cladded parts and the local technical slang used to describe the corrosion resistant protective layer applied on the carbon steel substrate (ie interchanging the expression of cladding with weld overlay, etc).
Personally I think that once the welding is involved in any way, there is no way you can demonstrate the soundness of your cladding, no matter how strong is your faith in your cladding process. Remember, to compromise the CRA barrier you need one only small weak point, not large internal area.
Consider this;- you might fabricate a stainless steel vessel, then build around it the carbon steel vessel tightly, then perform an explosive bonding of the internal vessel to the external one. Provided you do not make additional fabrication of any kind to this cladded vessel, then you might consider if you can safely overlook the NACE requirements for the base metal. I still have my reservations...did you check the entire surface of the CRA plate for manufacturing defects? Did you double check? If not, select the base material compliant with NACE requirements.
Cheers,
gr2vessels

 

[SJones]

The only thing that will be required for the carbon steel to notionally comply with ISO 15156-2 is a hardness of 22HRC. Was that achieved (by good fortune) in the parent steel and welds, including the HAZ from the weld overlay? If it was not, you are then into a risk and reliability assessment: reliability of the overlay NDT, reliability of the overlay in service and risk of failure of the carbon steel. Also, please note the use of the words 'long term'. 'Proper QA/QC' isn't 10 years in service!

Steve Jones
Materials & Corrosion Engineer

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

 

[Corgas]

sjones:

In this case, we are not considering weld overlay. Either explosion or roll bond cladding.

 

[SJones]

OK but you will still have to back weld any weld seams in the item under construction.

It's all a matter of risk. What does it cost to get the carbon steel with ISO 15156 requirements versus what will it cost (in people, assets, environment, reputation terms) if there is a loss of containment? Otherwise known as ALARP.



Steve Jones
Materials & Corrosion Engineer

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