I know what you mean, but i was no pointing on that aspect.
I'd like to be clear.
How many energy i need to add to 10 ton of steel to raise its temperature from 20ºC to 110ºC (as recommended by table 3.2)?. Really, i thought that need low energies, but when i was in front of piece with torch in hand, I noticed, that something was wrong. i made a simple calculus energies balance and heat flow out it was very high.
If i think in a oxy-fuel heater, when im heating an extreme, the other extreme (12m of distance) still its at 20ºC. If i think in a batery of heaters, i still have distorsion problems, because the other flange its cold. Then i think in a furnace or heating mantles, to develope homogeneus temperature and improve heat lost. Then my employer´s pocket says "comeback to earth". Then i read annex I and think: if laboratories test demonstrate that preheat its not necesary for single fillet welds, when hardness is less 400 HV. then think whats about multiple pass fillets welds.
For this reason, i wondered if you knew some method of preheating , inexpensive and effective for T-joints for the SAW process.
Regards.