I was listening to two old timers argue about weld preheat on a cold job site

One guy said he never bothers with preheat on anything under an inch thick, while the other insisted on it for any carbon steel below 40 degrees Fahrenheit. The second guy pulled out an old code book and showed the exact chart. I looked it up later, and he was right, it's in ASME Section IX. I've been skipping it on some smaller repairs in the winter, thinking it was just for big pressure vessels. Now I run my preheat gun for even the small stuff if the metal is cold to the touch. What's the coldest ambient temperature you'll work in before you call it for the day?

3 comments

3 Comments

abby_fisher4h ago

Feel for you on learning that lesson the hard way. I've definitely cut corners on preheat before and paid for it later with rework. My personal cutoff is about 20 degrees Fahrenheit if the wind isn't too bad.

jesse_smith102h ago

Wind matters more than the number, in my experience.

the_lucas1h ago

Yeah @jesse_smith10, I learned that the hard way last week with a 15 mph gust.