Scrap or Use-as-is 2

[annguyen]

Due to leaking valve, a spool of 6 inch, schedule 40S, charging pump suction piping (150 # class) was exposed to the discharge pressure for approximate 8 hours (2750 psi). We found out overpressure condition when the suction valve packing leaked. The pipe was made of SA312 TP304L. The temperature of the fluid in this event is 250F. The hoop stress is 32 ksi and the yield strength is approximately 20 ksi at temperature. We inspect the piping (OD measurement) and found no indication of problem. OD is still within the tolerance.

Consider the allowable stress for SA312 TP304 from B31.1. The allowable S stress can be approximate as 15.6 ksi. The longitudinal allowable stress for primary plus secondary stress is 2.5*S (equation 10) or 39 ksi.

Question: Do we have to scrap this portion of the piping? If not, can we justify using API 579-1/ASME FFS-1 2007 or other standards? Do you have any recommendation?

Regards,

An Nguyen

 

[metengr]

No, you do not need to scrap the exposed portion of piping. If you verified no visual and measurable swell, and perform a liquid PT of the OD surface to ensure no surface indications, this should be acceptable.

 

[annguyen]

Thank you for your response. Can you point me to any standards that allow me to do that? It seems to be wateful to scrap this pipe but I cannot find any standards or code to let me keep this pipe.

Again, thank you.

An Nguyen

 

[metengr]

An Nguyen;
Typically, an assessment is made after a problem is observed or detected. In this case, you used proper engineering judgment to conclude nothing was observed or detected with the exposed material.

Assessment methods like a basic visual inspection followed by surface NDT are Level I and Level II type assessments, which may not result in more sophisticated approaches, as would be found with Level III.

 

[rustbuster]

API-579 will also be a good guide

 

[Duwe6]

Stay away from NDT types -- Level II/III folks. Assessments of "Fitness for Service" is beyond thier training, ability and certification. The proper go-to guy for your pipe problem would be an API-570 certified pipe Inspector [or an API-510], or a pipe engineer.

And yes, I would happily sign a Use-As-Is disposition for your pipe, based on a lack of yielding as evidenced by the pipe still having a proper [unswelled] diameter. Think of it as a "really good hydro test".