European bolt material for ASME designed valve with PED Category IV

[chshbt]

Hi,

I am designing a high temperature steam shut off valve. The design pressure is 160 barG and temperature is 570 deg C. The design code is ASME Section Viii division 1. The body and bonnet material is A217-C12A. This is for an European customer and PED category required is IV. I have PMA for the body material.

My standard choice for the body bolting is Inconel 718 (UNS N077718). But cost of this material is going very high due to associated testing involved for PMA. In order to reduce the cost, I can select bolt material in European grade. The X19 (X19CrMoNbVN11-1) is an good candidate with same allowable stress of Inconel 718 and comparable creep resistance for high temperature. The thermal expansion also matches with C12A body material. If I use this material for bolting, there is no requirement for PMA and I can save cost.

But I am not sure whether it is allowed as per code to use dual certified materials in single component. The ASME requires code case when special material is used in pressure boundary. But being category IV design, all the calculation to be verified by notified body for PED. Is using dual certified materials for pressure boundary allowed in PED? Will notified body accepts this combination?

I really appreciate if anyone can shed some light on this topic.

 

[XL83NL]

Is using dual certified materials for pressure boundary allowed in PED? Will notified body accepts this combination?

In short; yes and yes. Why; as it meets both requirements. The NoBo therefore cant reject it.

I understand your issue. A PMA for a cat IV item needs to be countersigned by the NoBo. Im not sure if the PMA requires testing per se; Ive seen PMA's for e.g. A312 TP3xx pipe in cat IV applications, which were coutnersigned by the NoBo, without any testing involved. It was just a matter of paperwork. However your application is rather 'extreme' so I can understand the need for verified testing. On the other hand, Im pretty sure that if your design is acc. Section VIII, it'll be a good design. There will be nothing in the PED that will make your valve necessarily more 'safe', nonetheless it needs to meet the ESR's.

Dual certified material is allowed within the BPV. Refer e.g. to Sec II-D mand. app. 7. So if you MTR spells out the requires material spec and grade per what you require for Sec VIII, and applicable spec and grade what you require per PED, you're good. Another option would be if the MTR lists compliance with the PED 2014/68/EU. Dual certified marking is done all the time, e.g. 316/316L w/ 1.4401/1.4404 (thats even quadriple marking!)

Also review ASME PTB-10.

Do you have a copy of an MTR showing the dual certified material?

 

[chshbt]

Thank you XL83NL,

The additional test reports PMA requires for high temperature is tensile strength at the design temperature or higher and impact strength at the minimum ambient temperature.

For X19 (X19CrMoNbVN11-1) material dual certificate is not applicable because it is non-ASTM and non-ASME. I don't have the copy of ASME PTB-10. I'm trying to get one.

I don't have the copy of an MTR showing the dual certified material. May I will need to prepare the format.

I am having a dialogue with the Notified Body regarding X19 acceptance and any additional requirements.