Using improper filler wire for low alloy

By arash618 Date 06-25-2004 05:21

What happen, if we used Er-70s filler wire instead of Er-70S-A1 to weld Tube to Tube Sheet (Carbon Steel with 0.5%Mo) of an exchanger.

Tube content: Hydrogen
Tube content temperature: 450 C
Shell content: DM Water
Shell content temperature: 250 C

Tube Material: Carbon Steel with 0.5%Mo
Tube sheet Material: Carbon Steel with 0.5%Mo
Shell Material: Carbon Steel
It is my pleasure if you send me a refrence on WEB.

Thanks a lot.

By MBSims

Date 06-26-2004 01:26

What is the operating temperature?

By arash618 Date 06-26-2004 03:27

Shell content temperature: 250 C
Tube content temperature: 450 C

By MBSims

Date 06-26-2004 16:46

450 C (813 F) is high enough for graphitization to be a concern on the tube side. The weld is going to be less resistant to graphitization than the HAZ and could fail inservice. Probably wouldn't happen for awhile since you had some Mo pickup in the weld deposit from mixing with the base metals. If you're planning to run this a short time and replace the heat exchanger, you're probably OK for a year or two. If this is a new heat exchanger, you should discuss with the designer & customer, but probably will need to remove and reweld.

By Bill A

Date 06-29-2004 19:19

Isn't high temperature hydrogen attack (internal decarb.) a possibility at those temperatures if the hydrogen pressure is high enough? Carbon-1/2%Moly isn't great for resistance to that, but its better than carbon steel like ER-70S. (been awhile since I dealt with high temp reactions in hydrogen so I may be forgetting some details)