Common Bolt Type for PED (no special temperature requirement or corrosion resistance) 1

[servobrake]

What is the common go-to bolting in the EU for PED vessels? Any recommended suppliers?

Under ASME ASTM A193 B7 is perhaps the most common material for bolting for pressure vessels where there are no special temperature or corrosion resistance requirements. It is widely available and inexpensive.

Our current bolt is ASTM A193 B7 UNC 1.5-6 x 12 inch heavy hex head. We go to great trouble getting them compliant to PED because PED has the 27J Charpy impact requirement and mill certs do not have this test. We end up paying %2000 for EN10204 3.2 certification and have a PMA in our certification paperwork.

We'd like to just buy 500 of whatever people in the EU would use, importing from EU is fine if the paperwork is PED. We can change to metric threads if that makes it easier.

 

[XL83NL]

Yes. It’s not a good (or the best) practice, but we see it quite often that ‘PED-vessels’ with design to S8D1 have a few materials that may not be found in sec IIA or IIB. This is usually due to issues with sourcing or the very specific market we’re in. Nevertheless, the differences are often small, if any. Just make sure the material you’re substituting has mechanical and chemical properties equivalent to a grade found in IIA or IIB.

 

[servobrake]

Hmmm. Our Nobo separates material acceptability and stress allowables from calculation method. So he has not raised concerns regarding using ASME analysis and calculations on materials not on the ASME customary material list.

(Another bolt example). ASME lists ASTM A193 B7 bolts with a stress allowable. PED gives a different stress allowable for that same material based on A193 minimum tensile and yield stress.

For PED compliance he will let us use either allowable as the design allowable stress.

Similarly he has no objection to using a PED material (P355 barrel, for example) in a PED vessel using ASME analysis and calculation methods.

Basically he sees it as a PED vessel. We have to use materials approved by the PED system, using an ASME material is not sufficient. We can use an ASME material with a PMA if we have a Euro-spec MTR (EN10204, ISO9001 mill, etc).

In short the message I get is you can use ASME materials IF you meet all PED requirements, and if I am persuaded by your PMA, and you can always use PED materials, period

Is sounds like this is different from your understanding.

 

[XL83NL]

No, it is not different. My understanding is the same; if it needs to be acc. PED, you have to satisfy PED requirements. This can be done in various ways, as your NoBo pointed out.

However, what I principally disagree to with your NoBo, is that material (acceptability) and stress allowables need to follow design code. For example, if P355 is not a listed material in ASME II, then you may not use it for VIII-1 (or any other BPV) construction. Then your mixing up things, which is not a good practice. ASME code has a different basis for stress allowables then EN 13445.

So what you need to, if I understand correctly, is write a PMA for A193 B7 bolts. An example PMA and the procedure can be found here.

(Another bolt example). ASME lists ASTM A193 B7 bolts with a stress allowable. PED gives a different stress allowable for that same material based on A193 minimum tensile and yield stress.

For PED compliance he will let us use either allowable as the design allowable stress.

Make sure to use the stress allowable that's applicable for the code of construction that youre using.

 

[servobrake]

Thanks. I undertand both viewpoints. ASME and EN13445 can be viewed as unified wholes, with material (acceptability and allowables), and calculation (methodology & safety factors) considered interdependent.

This would clearly make sense if one code had higher safety factors on the calculation side and lower on the material side. But my understanding is that this is not the case, the calculation safety factors are similar.

EN13445/PED seems more stringent on the material side, emphasizing thorough-going quality control (ISO9001, impact testing in more cases).

From my position (I'm not an expert) both positions seem arguable. I wonder if you know of information that addresses this issue (searching "ASME" in the PED guidance only pulled up welding)

 

[XL83NL]

But my understanding is that this is not the case, the calculation safety factors are similar.

No, theyre different.

https://files.asme.org/catalog/stllc/printbook/20775.pdf

(free purchase here)

http://www.unm.fr/main/download.php?file=144_FICHIER_0.pdf

https://www.netinform.org/GW/files/pdf/Kauer_DGT.pdf

http://www-eng.lbl.gov/~shuman/NEXT...ssure_vessels/US_vs_EU_material_strengths.pdf

https://www.researchgate.net/public...re_Vessel_Codes_ASME_Section_VIII_and_EN13445

I wonder if you know of information that addresses this issue

Which issue do you exactly mean?