PSA: I've been preheating furnace tubes all wrong for 15 years

I was at a job in Gary, Indiana last month and a veteran boilermaker named Pete watched me do my usual routine on a tube bundle. He just shook his head and showed me I was using way too much flame too fast, causing uneven expansion. Now I start with a low heat for 10 minutes at 200 degrees before cranking it up. Has anyone else had a moment where a simple tip from an old timer completely changed how you work?

2 comments

2 Comments

the_sage1mo ago

Nah, I gotta push back on this one. I've been doing tube work for over a decade and rushing the heat has never been an issue for me as long as you know your equipment. If you're using a modern torch with good gas control, you can bring it up to temp in like 5 minutes without warping anything. Pete might have been right for his era with old school gear or a specific alloy, but low and slow for 10 minutes is overkill for standard carbon steel. A lot of those old timer tricks are based on tools that don't exist anymore or conditions that aren't typical. Just watch the color change and listen for the expansion sounds, that's what matters.

the_hugo1mo ago

Haven't you heard that rapid heating can cause micro-cracks even if you don't see visible warping? I've seen a few frames fail down the road from people who swore by fast heat cycles. It might work for a while, but there's a good reason old timers took their time with it.