Joint Efficiency Issues With 1964 LPG Storage Tank 3

[Tysoo2]

Hey all, We are performing Compress code calculations in preparation for a CRN application for an LPG storage vessel in Saskatchewan Canada. The Vessel already has a CRN in Ontario as that is where it was initially constructed and installed. My issue is that it was sold and moved into Saskatchewan prior to the jurisdiction having authority caring about CRN's applicable to their province. Regardless it has come to light that there is not a valid SK CRN for this vessel so we have been contracted to perform the calculations and submit a CRN application package on behalf of the vessel owner.

To get down to the nitty gritty of it, we have issues. Firstly, the vessel was constructed of SA212-B using the 1964 code which I'm not sure of the code implications since that material was replaced by 516-70 in 1964 and SA-212B isn't listed in any code editions after 1962. Secondly the U1A does not state the extent of radiography performed. The data plate has P.X.R. stamped on it under the ASME and U symbols which I understand to mean Partial Radiography. Using this information we can assume at best that we are working with a joint efficiency of 0.85 for spot RT UW-11(b) for the long and circ seams. with a min. thickness of 0.937" and a basic allowable stress of 17,500Psi for SA-212-B @100°F we are left with a MAWP of only 219.8Psi, and we need a MAWP of 250Psi.

From what I can understand is that the engineers originally used a joint efficiency of 1.00 during the original calculations which is what gave them the 250Psi MAWP. However, I believe there was a mistake made either at the time of the design or to the extent that the radiography was performed.

If all my math is correct and my assumptions are correct someone either made a mistake while the vessel was being designed or radiographed, or there was some allowance in the code to use a joint efficiency of 1.00 in some instances I'm unaware of.

Anyways, any insight or suggestions would be greatly appreciated. Otherwise we are looking at performing full radiography of the vessel and performing a modification prior to the CRN submission, but that adds a lot of extra cost, and we would like to avoid that.

I have attached the original U1A for the vessel for reference.

Thanks,

 

[IdanPV]

Does re-rating of the vessel is something you can do?
Perhaps 219.8 would be enough?

 

[Tysoo2]

Hey @IdanPV, the governing code for vessels in propane service CSA B149.2 here in Canada and it requires that all propane storage vessels have a 250PSi MAWP. so unfortunately we aren't allowed to derate and maintain it in LPG service.

 

[JStephen]

Were the longitudinal seams fully-radiographed with joint efficiency of 1 while circumferential seams were spot-radiographed or not radiographed? If so, would stamping have been that same P.X.R? That would seem to be the logical way to design it.

 

[Tysoo2]

Part of the issue is we have no knowledge of the extent of the radiography beyond the P.X.R stamp so we have to assume that spot radiography was all that was performed being the worst case scenario. Using Compress updating just the long seam to Full RT does not change the MAWP. This should be true as to qualify your design with a joint efficiency of 1.00 you need to meet the requirements of UW-12(A) which inherently requires full radiography of all joints. So if you fully RT the entire vessel except for the circ seems that still qualifies you as partial radiography under UW-12(b).

at least I think haha.

Thanks,

 

[Tysoo2]

As far as I can tell by looking at the U1A it specifies UW-12(A) & (b) for my code paragraph so I'm assuming this would be as JStephen Stated having the long seams fully radiographed and the circ seams spot radiographed. this would qualify as full radiography as per UW-11(A)(5)(-B) (in the modern code) and allow for a modern day RT2 stamp on the data plate hence the P.X.R. This should allow us to use the 1.00 joint efficiency I believe. We are however making an assumption that this is what was done but it makes logical sense.

 

[Geoff13]

Have you discussed your plan to get a new CRN with TSASK? Seems very odd to try to get a new CRN for a vessel built 60 years ago. No point doing all this work if TSASK won't allow it. I'm more familiar with chatting with ABSA, but they are always very helpful with unique questions like this. I can't imagine TSASK issuing a new CRN for design conforming to the 1964 Code, and the materials won't meet the current Code.

As there is already a CRN registered on Ontario, will TSASK simply accept that. I believe they would on a brand new vessel, but again this is 60 years old.

A real long shot, but have you asked TSSA in Ontario if they have any of the original CRN records in their files. Might not help in the registration, but could give you further info about the original fabrication. Similarly, have you contacted TIW (Link) to see if they have any files. I know we keep PV records "indefinitely" so perhaps they are similar.

The CRN merely registers the design. The vessel must then be separately registered as a vessel built to that CRN. Can't imagine how you can do this with no fabrication records.

As a designer/manufacturer I'm going to toss out "The vessel is 60 years old. You've had full value. Perhaps it's time to buy a new vessel?".

Good luck
Geoff

 

[Tysoo2]

Hey Geoff, So I have spoken with TSASK, they require all used pressure equipment being imported into SK to have a valid SK CRN#. It was discovered that the vessel did not have a SK CRN number so we are required to submit as-built drawings as well as code calculations, TSASK will review and assign a CRN number for use in Saskatchewan. that's the TLDR version at least, if your interested i have attached the "Requirements For The Acceptance of Used Pressure Vessels" as published by TSASK. They can actually require you to replace non-standard nozzles if not included in the U1A which may be something we run into also.

 

[georgeverghese]

Any chance of getting this CRN when there is no charpy impact test certificate for -40degF lower design temp?

 

[Geoff13]

As a designer/manufacturer I'm used to the new vessel rules. Interesting to learn what owner/operators have to do. Thanks for the attachment.
Good luck.

 

[Tysoo2]

Not sure, it was originally accepted for use in Ontario without it so they may let it slide, we are only shooting for an MDMT of -20°F anyways as that was what the vessel originally was and we don't want to perform an alteration.

Geoff, thanks for your input, used equipment is always fun haha!

 

[jt1234]

As I have dealt with revamp with vessels using 1960's code and with so called 212 boxed material (B for "boxed" if my memory serves correctly.), be cautious of the following:
1. It already exceeds the normal design life of 20-30 years. You are running tremendous risk of failure regardless how good you reconstruct the stress analysis or any paper works. Carbonization or graphitization through years will make the material brittle as well as reduce the tensile strength. What we did is to cut a sample and sent to lab for analysis. Whoever approves your calculation, CRN#, or giving you a green light to use, is going to take the legal responsibility. If failure in operating and injuring people, court or jail time for sure.
2. Beyond all paper works you try to reconstruct, which has no guarantee the vessel will be good, I will recommend to re-do hydrotest based on the original test pressure. If fails, you save lives, no one go to court, and it is time to get a new one.

The purpose of the code is solely based on one thing: "Safety", that is what I keep telling young engineers in my company. Radiography or UT is not mandatory(0.7 JE per code),and no guarantee the vessel is good for service solely based on NDE. But hydrotest, which is to simulate design condition, is mandatory to prove it can be safe in design condition, regardless at 2000 degF or 3000 psig.

 

[Tysoo2]

Hey JT, I understand the issues regarding the material itself, The US Department of Commerce actually performed a detailed post accident analysis on the head of a steam boiler that was involved in a rail road accident on behalf of the Federal Railroad Administration. It goes into excellent detail regarding the issues and limitations of SA-212-B. I've attached the link for anyone interested.

https://www.govinfo.gov/content/pkg...VPUB-C13-2fb65e7faaf25af9c0e9e6eb77d081dd.pdf

Regardless of my own feelings regarding the useful life span of vessels or the issues regarding embrittlement with SA-212-b, We have only been contracted to perform code calculations, we are not required to even stamp said calculations. At the end of the day it is not our equipment and without laws backing us up or giving us power to remove it from service, all we can do is what we are asked. The unfortunate mindset in the propane industry is that since the product is non-corrosive the vessels should last forever, and if its been in service safely since the 1960's why should it now be unsafe when nothing has changed. Also we likely will not be performing a hydrostatic test as the TSASK does not require it for a CRN submission on used pressure equipment.

TSASK (Technical Safety Authority of Saskatchewan) may however require the non-standard nozzles that in the vessel that have not been listed on the U1A from to be removed and replaced with ones properly stamped so that may end up actually condemning the vessel due to cost, but otherwise we will see what the customer determines is best.

 

[georgeverghese]

See if this helps - loss of containment from brittle failure for non compliant legacy vessels can happen anytime without prior warning.

https://engineer.ca/on_pst_brittle.htm

 

[Tysoo2]

In a perfect world people would replace this old iron with something safer, but the people who own these vessels are not the same people who understand the mechanical issues like those of us in this thread and on this forum. We can recommend they be removed from service due to all the aforementioned potential issues, but in Canada, if there isn't an immediately unsafe condition that can be reported to the authority having jurisdiction, as long as it passes the required NDE it stays in service.