PWHT of AR Plate

[Ploman]

Gents,
I will be welding an AR plate, 500 Brinnell on a wear surface inside a pressure vessel.
Due to thickness, I am required to PWHT the vessel per ASME to approximately 100 F for 1.5 hours.
How will this affect the abrasion resistance of my wear surface.

 

[weldstan]

There will be loss of hardness with PWHT at 1100 F min for 1.5 hours. Can you not fillet weld the AR plate to the vessel after it has been PWHT'd?

 

[Ploman]

Thanks Weldstan- Unfortunately I can't go that route for 2 reasons, either of which is not acceptable. !. ASME does not allow welding on a vessel which has been PWHT. All welding must be completed prior to PWHT. Secondly, the vessel is too small for access after it is welded. In the past, I have used a sacrificial wear plate of 1"+ thickness. I am attempting to reduce the weight and cost, and increase the lifespan of the part.

 

[metengr]

I would agree with weldstan. Your other option is to use a hardfacing (Stellite 6) weld overlay on steel plate.

 

[Ploman]

Metengr- will the stellite overlay be less affected by the PWHT cycle?

 

[metengr]

The hardness of the Stellite 6 overlay will not be affected by PWHT. However, I want to caution you to be sure Stellite 6 is the correct selection for you in this application. There are other hardfacing options to consider depending on the abrasive environment.

 

[Ploman]

The abrasive media is frac sand. Fortunately, frac sand is roughly spherical, so it is somewhat less aggressive than if it was angular. The wear areas will be subjected to more or less a continuous shot-peen. Still, it can wash out valve internals sometimes in hours or even minutes.

 

Attach an intermediate plate (poison pad) to the vessel before PWHT; then after PWHT weld the wear plate to the pad. The intermediate plate should be of thickness and material such that PWHT is not mandatory.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[Ploman]

Good info all, and thanks for your responses.