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 The tower is of ASTM A-70 which is withdrawn but I am considering it to be a medium carbon steel with SMYS of 55ksi.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