EN 1092-1 flanges bolting material requirements (A2-70???) 2

[GD_P]

Hello forum,

For using EN 1092-1 flanges with their PN rating, what is the bolting requirement?
In the normative annex E, Cl.E.3.4,
"- Bolt material:
≤ M39: nominal design stress at operation 200 MPa, at assembly and testing 285,7 MPa;"
In my opinion this can be considered as min. requirement.

Now the concern is, can we use EN ISO 3506-1, A2-70 grade (ultimate strength = 700 MPa, yield strength = 450 MPa) bolts for EN1092-1 flanges?
For testing condition 285.7 < 450,so this is okay.
but for operating condition, how to calculate the yield strength of A2-70 bolt at operating temperature (250 deg C in my case)?

FYI: I am using 2 o-rings (PTFE) for sealing instead of gasket.

Thanks in advance.

GD_P

 

[XL83NL]

Well, first of all, PTFE O-rings at 250 °C isnt a good idea. I'd stop using PTFE @ 200 °C operating, maybe go to 230 °C for short term peaks (or design).
Have you check if the standard of application (e.g. EN 13445 or 13480) tells something on this subject? They might refer to EN 10269, or EN 1515-1 or 1515-4, which can be of guidance as well.

 

[GD_P]

"I'd stop using PTFE @ 200 °C operating"
Yes we do the same. For 250 deg C, suitable sealing material is used.
EN 1092-1, refer EN 1515-1 & 1515-2 for bolting.
From EN 1515-1 give info about
1) Bolting mat / grade & corresponding dimension standard for bolts.
2) Bolting mat / grade service limits i.e., temp & PN class.
Whereas EN 1515-2 gives info about
1) Bolt mat / grade classification strength wrt flange material (classified in EN 1092-1).

Isn't EN 1515-1 is sufficient for selection of the bolting?
What to do after EN 1515-2 classification :low, normal & high etc.

GD_P

 

[XL83NL]

Can the EN 1515-series help, or do you have a specific question?

your OP says youre using PTFE, which isnt suitable imho. Or am I missing something?

 

[GD_P]

Sealing type (gasket or O-rings) are decided by the process engineers, where as I deal with mechanical work.

Anyway the que is, why should we refer the EN 1515-2, when EN 1515-1 gives the bolting selection?
As EN 1515-2 gives bolting strength classification & lets say my bolts are low strength, then what?
Does this change the PN rating of the flange assembly (flanges & bolts together)?
What is one suppose to interpret from the strength classification?

GD_P

 

[KVdA]

Because there might be other standards to consider as well, using the teams high/intermediate/low strength bolting.
As long as there are no contradictions i’m already happy

 

[GD_P]

One more point,

Why 1515-1 do not allow ISO 4017 bolts whereas EN 1515-4 allow?
When to refer EN 1515-4?
As I am referring En 1092-1 flanges, this std refers to EN 1515-1 & EN 1515-2 for bolting.

In ASME, flange calculations require allowable stresses which are given in the ASME sec.II D for all permissible temp ranges,
whereas in EN where we can get the allowable stress at temperatures other than room temp.
It will be grateful, if someone will explain this.

GD_P

 

[GD_P]

Also in EN 1515-2, Clause no. 3
"WARNING Bold materials 4.6 and 6.8 are not intended for the use in the scope of the Pressure Equipment Directive."

Why PED prohibits the use of 4.6 & 6.8 grade fastener?



GD_P

 

[MGZmechanical]

Hi, I think you have some properties at high temperature in ISO 3506. See this document from Schaefer.

https://www.schaefer-peters.com/uploads/tx_kkdownloader/Technical-Information_S_P_06.pdf

The exact reasons why some materials and bolt grades are in or out in the list of approved materials for the PED is a mistery for me. Specially because in many cases when you ask to a notified body they just give a PMA for that material without problem (e.g. S235JR, S355J2,...) Probably it's easy to get a PMA for 6.8 but in this case I would just use 8.8 grade (they're very common).

Best regards,

 

[GD_P]

@ManoloGalarraga
Thanks for you response.
Yes I found it but same is not clear for ISO 898-1 grades.
The annex B says "Up to typical service temperatures of 150 °C, no detrimental effects due to a change of mechanical properties of fasteners are known."
And please refer pg no 8 of below pdf

https://www.wuerth-industrie.com/we...al/dinokapitel/Kapitel_01_DINO_techn_Teil.pdf

Not sure what to consider.

GD_P