Use of Composite materials to alter ASME pressure vessels 1

[koshyeng]

Dear experts,

ASME PCC-2 is a post construction code for vessel repairs and alterations using composite materials. I need to repair cracks in of our pressure vessel and composite materials using PCC-2 code will improve the vessel integrity with minimum risk.

NBIC inspector, who will be issuing R stamp after alterations mentioned that NBIC does not recognize use of composite materials to alter or repair the vessel. So, he won;t be able to approve the vessel alteration procedure.

I would like to know if any you have came across this situation? Appreciate for your help.

Thanks
Koshy

 

[metengr]

The Inspector is correct. What kind of composite materials are you using for repair or alteration? Are these materials endorsed by the original code of construction?

 

[jte]

koshy-

Strictly speaking, ASME PCC is a standard, not a code (the second "C" stands for "committee"). And PCC-2 covers nonmetallic repairs as one of several methods. It is a standard which provides guidance, but must be worked within jurisdictional requirements and must be consistent with the original code of construction.

As metengr points out, it would be quite surprising to me if an AI were to approve a nonmetallic repair to a stamped vessel. There's just very little precedent and its difficult to tie metallic materials to the nonmetallic from a Section VIII perspective. In my experience NMR's are primarily used on piping and pipelines.

Having said that, I've seen NMR's on vessels, so clearly it can be and has been done. Physically. Now, the jurisdictional legality of one installation I've seen in a US state was questionable. The jurisdiction with authority over that site is fairly savvy, although understandably conservative. I would consider approaching them for approval for such a repair, and I suspect that upon consideration they might approve. But I would only use this approach as a short term fix, with the expectation that it be repaired "properly" at the next planned shutdown.

If I were approached for a NMR to a vessel, say a thinned boot on a horizontal vessel, I'd certainly entertain the proposal. If it were for one of our overseas operations with minimal or no jurisdictional oversight that would simplify the decision making, but at the end of the day, me or people I know are taking responsible charge for that repair and its safety relative to the people exposed to a potential failure. My company has some decent oversight of NMR's both in terms of situations where they may be used, and on specific products which we've independently tested and vetted. Just keep in mind that a salesman's promises as to the product's characteristics are put forth by somebody with an inherent conflict of interest. Independent testing can weed some poor performers out pretty quickly.

Given that you self-identify as a chemical engineer, and the fact that you are asking for mechanical engineering help not from within your own organization but from an internet forum with anonymous replies, and further that what you are proposing is, while not unheard of, certainly not conventional, I'll suggest that you are probably best off going with a metallic repair designed by competent mechanical engineers and installed by competent craftsmen.

 

[koshyeng]

metengr,

Composite material is CFRP. The thickness of the material and the grade selected upon engineering calculations will be equivalent to our current material and pressure ratings.

jte,

Thanks for your response. I am least inclined towards this approach but I was asked to evaluate this option. I do not have any experience on such materials and hence I posted here to know if the forum members has any prior experience.

Even though I have a dual degree and being mechanical reliability background, by no means I am expert at ASME/NBIC codes. I see this forum as a platform to exchange and seek advise/recommendation from experienced professionals.

Thank You

 

[PMCap]

Where are the cracks located and how large an area needs to be repaired? Can you cut out the area where the cracks are located? Can you drill crack ends and terminate the cracks?

 

[metengr]

Koshyeng
The NBIC is about traceability and documentation regarding materials and welding for repairs or alterations to pressure retaining items. The bottom line is the NBIC does not specifically address CFRP for repair or alteration to metallic PRI.

So, you either conduct the alteration and have it approved by an insurance company IF the vessel is not under any Jurisdiction or have the Jurisdiction approve it if regulated.

 

[PMCap]

The NBIC does not currently prohibit restoration by encapsulation of a degraded area which is a means of implementing an ASME code restoration. Cracks would need to be removed or terminated or the area with cracks removed. Let me know if you need additional information on this method of restoration. The method can be implemented in a timely fashion and is quite cost effective.

 

[XL83NL]

This blog from Becht's company may perhaps be of use in this context;

https://becht.com/blog/repair-of-pressure-equipment-and-piping-in-nuclear-power-plants