We are buying some plate material c

[PresDes]

We are buying some plate material conforming to SA516Gr70. The Nb content in the product was found to be 0.05%. As per SA20-Table 1-Note D, Nb in product should be limited to 0.03%, but higher content up to 0.05% may be accepted by agreement between purchaser and seller. This plate is meant for shell and dished head of a vessel which is in Hydrogen service. The thickness of the plate is 32mm for Dish, and 28mm for the shell. The design temperature of the equipment is 150 DegC, while the normal operating temperature is 120 DegC. Please share your views, and guide.

 

[metengr]

Niobium (Nb) is a micro-alloy element that increases strength using lower carbon content and is a grain refiner for improved notch toughness. With that said, since I prefer lower micro-alloy contents to ensure improved weldability, I would look elsewhere for SA 516 Gr 70.

 

[weldstan]

Tend to agree with metengr; find another supplier.
The following questions should be addressed if you intend to use. Was Al used for fine grain melting? Will the head be tempered after forming? Is impact testing required? Will PWHT be required for service?