Changed my mind about pre-heating on the big retrofit in Toledo

I was working on the old coal boiler retrofit at the power plant there last fall. The foreman insisted we pre-heat the new economizer sections to 250 degrees before welding, which I thought was overkill for the schedule we had. After three days, we had zero cracks on the pressure welds, while the crew on the other unit that skipped it had to redo four major seams. The extra six hours up front saved us two full days of repair work. Anyone have a different method that works just as well without the big heat rig?

3 comments

3 Comments

flores.tessa1mo ago

We had a similar spec on the turbine casing at the Pine Bend refinery last year. The procedure called for a 200-degree preheat with ceramic blankets, and it felt like a waste of a whole shift. But after seeing the other crew fight with stress cracks all week, I got it. Sometimes the book is right, even when it hurts the schedule.

cameron7631mo ago

Ever try a lower temp but hold it longer? I've heard some crews get away with 150 degrees if they soak the joint for a full shift before the weld.

wright.drew25d ago

Hold on, how do you know it was the pre-heat that saved you and not just better luck with the steel that day? I've seen crews skip pre-heat entirely on plenty of boiler jobs and never had a single crack, just used a good controlled cooling process with slow passes. Sometimes the "book spec" is just CYA from the engineer who doesn't want to get sued, not an actual proven requirement for that exact metal thickness. You probably wasted your six hours of setup time, and the other crew just got a bad batch of material or had a rookie running the root pass. That foreman selling you on the pre-heat saved his own reputation, not the schedule.

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