use of A333 gr6 for steam & feedwater service

[pipe15]

our material guys are considering going from 106b to 333gr6 for steam and feedwater service (600 deg, 1200psig)due to..

"The proposed material, A 333 Grade 6, has similar ultimate strength characteristics. In addition, the material specification for A 333 Grade 6 includes toughness characteristics (e.g., Charpy V-notch impact toughness tests..."

I see that 333gr6 does have these additional properties in low temp service, but what about when it is not used in low temp service? what do I gain using a333gr6 when not for low temp?

thanks

 

[JStephen]

Seems like back several years ago, when I was looking at different nozzle material, I found that you also gain a dramatic increase in price. Maybe it was because we just needed small quantities.

 

[DSB123]

pipe15,
JStephen is correct. Perhaps your material guys have shares in the material!!! Suggest you challenge their ideas of departing from "standard" materials for steam and feedwater.

 

[robsalv]

! what they already said.

IMHO, you gain nothing, except a lighter wallet.

ASTM A106 is a more than suitable standard for CS in elevated temperature service. What brittle failure risk scenario could there possibly be at higher temps?

Pipe15, ask your material guys what toughness CVN's values are they looking for. I'd bet that the A106b would easily meet it at the operating temperature... You can buy a lot of impact tests for the price difference between A106 grB and A333 gr6.

Cheers
Rob