Our shop's weld failure rate dropped from 8% to under 1% in a year after we switched to a new pre-heat method.

We were doing a lot of heavy plate work on some pressure vessels for a refinery job, and our X-ray callbacks were killing us, mostly on the root passes. The old foreman swore by just hitting the joint with a rosebud torch for a minute, but the readings were always spotty. About a year ago, we started using ceramic heating blankets with digital controllers on every single critical weld, no exceptions. We set it to hold at 250 degrees F for the full pre-heat and interpass temp. The difference was night and day. The welds just laid in smoother, the penetration was consistent, and the guys said the arc felt better. It added maybe 20 minutes to the setup for each section, but saving all that rework time and material more than made up for it. Has anyone else seen results this good from tightening up their heat control, or did we just have a bad process before?

3 comments

3 Comments

parkera221mo ago

Yeah, we had the same problem on some structural stuff. Switched to induction heaters for pre-heat and our UT rejection rate basically vanished. The controlled soak is everything.

jesse9941mo ago

Holy cow, you guys were just using a rosebud torch before?

jamesm481mo ago

We had a 20 inch diameter, 2 inch wall pipe come back with a cold crack a few years back. I was one of those guys who thought a rosebud torch was good enough for pre-heat. Seeing that repair job and the downtime it caused changed my mind real quick. We switched to an induction setup for that pre-heat step and it's night and day. The heat is even, you don't have to babysit it, and we haven't had a single rejection on a weld since. I won't go back to a torch for anything critical now.