Pressure-bearing parts other than main pressure-bearing in the Pressure Equipment Directive

[men8th]

If designing a vessel or piping under the Pressure Equipment Directive (PED) using EN13445 or EN13480, requirements for material certification (3.1, 3.2, 2.1 or 2.2) are given in EN764-5. In EN764-5 is a flow chart which defines the requirements for "main pressure-bearing parts" and "pressure-bearing parts other than main pressure-bearing". Can anyone give an example of a "pressure-bearing parts other than main pressure-bearing"? I've read PED guidelines 7/5, 7/6, 7/8 and 7/15 but there is not much specific information in there. My guesses of what "pressure-bearing parts other than main pressure-bearing" might be:
[ul]
[li]Bolting, apart from where failure of a single bolt cannot be tolerated? For example flange bolting would be 2.2 cert; Any specialised design where the bolting is not redundant, eg a quick acting closure held shut with a single threaded fastener (horrible design, sounds like an industrial accident waiting to happen, but given for an example here) would be 3.1 cert.[/li]
[li]Weld consumables?[/li]
[li]Stays, gussets and stiffeners used for shell strength?[/li]
[li]Others?[/li]
[/ul]
Does anyone have any experience with this?

 

[XL83NL]

This thread may provide some leads;

https://www.eng-tips.com/viewthread.cfm?qid=450446

Other than that, I hvent foudn NoBo's to be so exact or determinate on this subject. However, 3.1 has become a standard, in that it is often supplied free or with little extra charge. As such, what I usually see is that a 3.1 CMTR is supplied regardless if the PED or EN764-5 requires 3.1 or not.

 

[chicopee]

I may be able to help you even though I am not familiar with the documents that you listed. I believe that the term "pressure bearing parts" is a term synonymous to bearing stress, a topic that you'll find in strength of material and machine design text books. The stress in those text books is calculated by dividing the force on a part divided by the cross sectional area of that part to which you want to determine the stress. Basically it is a contact stress.

 

[XL83NL]

Im pretty sure this is not what OP meant. This matter deals with a topic of the PED that often leads to confusion. Do you have experience with the PED, chicopee?

 

[men8th]

Thanks @XL83NL. I've read that post and a couple of similar ones but it's not really giving me the clarity I was looking for. I'm really struggling to decide really if there are any parts, "main pressure-bearing" or "other than main-pressure bearing" where there is no need to get a 3.1 cert. As you mention. 3.1 CMTR is very widely available, so why wouldn't you ask for it.