Bolting class 12.9 at 350 °C design code AD-2000 3

[JamyFilter]

Hello,
Does anyone know if bolts class 12.9 can be used at a temperature of 350 [°C] with design code AD-2000?
As per first information, an inspector told us upper limit is 300 [°C].

Thanks a lot for your reply. If you can supply, I am interested in the reference you use to reply.
Regards

 

[CoryPad]

I cannot answer regarding AD-2000. Here is what ISO 898-1 says:

"Elevated temperatures can cause changes in the mechanical properties and in the functional performance of a fastener."
"Up to typical service temperatures of 150 °C, no detrimental effects due to a change of mechanical properties of fasteners are known. At temperatures over 150 °C and up to a maximum temperature of 300 °C, the functional performance of fasteners should be ensured by careful examination."
"Information for the selection and application of steels for use at elevated temperatures is given, for example, in EN 10269 and in ASTM F2281."

EN 10269 has data for various alloys at various temperatures, however nothing that would be property class 12.9 at 300 °C or above.

 

[TWP]

Read the German standard called "AD 2000 Merkblatt W7" (materials for pressure vessels, Bolts and nuts made from ferritic steels); 2014-11
There are a lot of limitations in this standards. Lower temp. limit for 8.8 and 5.6 not below -10C. Pressure also limited.
Grade 12.9 seems not to be listed>> not allowed.
300 Celius seems to be the upper limit for certain standard grades such as 8.8 and 5.6. (ISO 898)
Perhaps not available in english.
In europe PED requirements apply as weel (european pressure equipment directive)
Good luck

 

[XL83NL]

AD2000 is not a harmonzied standard but has some appendices that guide you to compliance with the PED, so that shouldnt be a problem.
Is it allowed to use B7 bolts (or at least the EN-variant for those bolts EN 10269 42CrMo4 / 1.7225)?

 

[TWP]

EN 10269 is well known in europe under EN 13480 (piping) and EN 13445 (pr. vessels).
EN 1515 deals with bolting for flanges (Flanges and their joints — Bolting.
42crmo4 is part of a.m. EN standards.

EN 1515
Part 1: Selection of bolting
Part 2: Classification of bolt materials for steel flanges, PN designated
Part 3: Classification of bolt materials for steel flanges, class designated
Part 4: Selection of bolting for equipment subject to the Pressure Equipment Directive 97/23/EC

I do use a lot of B7 studs with 2H nuts under PED.
Subject to acceptance of customer and notifying bodies; but normally no big problem.
Occasionally I prepare/ write a so called PMA; Particular Material Appraisal in order to get B7/2H accepted for a certain client/ application.

42Crmo4 hardly used in comb. with UNC/ UN threaded studs/ nuts; only with metric threaded parts.