Can pipeline alignment be done by heating?
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Our factory is currently working on piping installation. Since the quality of the materials is not very good, there is a significant misalignment between the elbows and the pipes. The construction team uses welding to heat them up and then hits them with hammers. Is this method in compliance with the standards? Will it have an adverse effect on the pipes? Will it reduce the performance of the welded area? The pipe material is 20#. Another issue is that the pipes are misaligned; the construction team then uses heat to warm them and pours water on them, which allows the pipes to return to their proper position. The construction team said it’s fine to heat the carbon steel pipes; they do that all the time. I don’t understand why, but common sense tells me that heating them with fire shouldn’t be right. Moreover, after heating them, they poured water on them – surely that makes the pipes more brittle? They say that carbon steel pipes can be heated with fire, but stainless steel pipes cannot. Could someone please explain to me whether their approach is correct? Thank you all!
In any case, these practices do not meet the standard requirements.
Could you theoretically explain why doing this is not a good idea?
I’ve also seen unembossed steel pipes welded using gas cutting! The company’s welders often do this! It’s more or less what I said – after baking, just use water, which helps it cool down quickly and makes things easier. I’m not sure if it’s possible to do this; I don’t know much about pipes
With low pressure, it is a non-flammable and non-explosive medium, as well as a non-toxic medium; it is indeed possible to do this.
To be precise, methods involving compressed pyrotechnic correction are not allowed. You can figure out what the temperature is for pyrotechnic heating just by thinking about it. .
In my opinion, on-site flame heating is permitted by the standards, but under certain conditions. 1. The site does not have the conditions for electric heating ； 2. When the preheating temperature is low, the pipe wall thickness is thin, and the pipe diameter is small ； 3. Low-alloy steel is acceptable, but pipes such as P5 and P9 are definitely not suitable ； Additionally, plasma is generally used for cutting stainless steel pipes, while flame cutting is rare; it results in wide cut gaps, and the polycarbon layer formed by processes like carbon rod gouging affects the welding quality.
It is permissible to use a hammer to relieve stress; for the fillet welds of our hydrogen production pigtail tubes, hammering was used after each layer was welded in order to eliminate welding stress.