preheat instead of PWHT?

By nateprice215 Date 08-30-2007 13:12

Hello:

We are performing some repairs to some ladder and insulation clips on a tower. The tower is of ASTM A-70 which is withdrawn but I am considering it to be a medium carbon steel with SMYS of 55ksi. My question is this; if all the welds are just fillet welds, and we use a preheat, would this arrangement still result in a hard HAZ on the ID of the vessel? This vessel is in a service that recommend/requires PWHT. I am wondering if I can get around this by a high preheat say 250°F?

Any help is appreciated,

Nate

By js55

Date 08-30-2007 13:48

There are exceptions to PWHT in some codes even when the material thickness requires PWHT(for example B31.3 and throat thickness allowances). But in order to determine specifically if this applies to you, you need to tell us what code you are working to. And maybe give us a little more info on the material so that we don't have to look it up. though I'm sure ther'e a few fellas in here know this stuff by memory. I ain't one of them.

By jon20013 (*****)

Date 08-30-2007 15:05

I fully agree with js55 but further wonder about the recommendation / requirement of PWHT in the application you describe. Like js55 said, let us know which code it is you're working with and we'll be able to advise further.