Regarding the welding between the flange and the pipe
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To help everyone achieve greater accuracy during the detailed design, should the welding between flanges and pipe fittings (mainly elbows) be carried out in a prefabrication plant or on-site? Please explain in several aspects based on what is connected between the flanges. It turned out to have been sent by mistake to the process system. .
Flanges can be connected to elbows, tees, crosses, and straight pipe sections, but where possible, direct connections of flanges to elbows and crosses should be minimized; it is best to include straight pipe sections instead. Both prefabrication in a factory and on-site fabrication can ensure welding quality. More prefabrication work should be added.
"Try to minimize direct connections between flanges and elbows as well as tees; it’s better to include straight pipe sections. It’s easy to say, but difficult to put into practice. We also want our pipelines to be designed that way, but... . . Alas! !
The flange and the pipe can be welded directly, and there is no problem with that. It doesn’t matter whether a short circuit is used between the flange and other pipe fittings, but some sources suggest that it’s better to use one. Can this be understood as meaning that for important pipelines, a short circuit can be used if space permits?
If it’s a short elbow (without a straight section) or a short-diameter tee, can’t it be welded to a flange without a straight section?
Elbows are fine; it’s best not to weld tees directly to flanges, as bolts are difficult to install in that case.
It’s going off track; what’s being discussed is prefabrication in the workshop. So, could transportation cause damage to the flanges?
Pre-fabricated straight sections can be used, but they are costly and time-consuming, and are suitable for applications with high requirements. Welding is carried out on-site without using pre-fabricated sections, which results in lower costs and shorter construction times, making it suitable for applications with lower requirements
It’s pre-made; during transportation, just protect the weld joints and sealing surfaces properly, as normal transportation won’t cause any damage
Factory prefabrication and on-site welding are actually the same; it’s just necessary to protect the flange surfaces during transportation! (For transportation, refer to the manufacturer’s packaging guidelines.)
NOTE: Socket weld flanges cannot be welded directly to socket weld pipe fittings; they need to be treated separately. There must be a straight pipe section.: (
Flanges and pipe fittings can be welded directly in either the prefabrication workshop or on-site; there is no difference in terms of welding. Prefabrication is done merely to reduce the workload on site. Since it is easier and faster to carry out work in the prefabrication workshop, as much work as possible is completed there, allowing for smoother construction once work starts on-site.
----------------------------------- The pipeline is divided into several sections; the flange ends are protected, and supports are placed beneath the pipeline. These supports are positioned directly on the platform, allowing the pipeline to remain unstressed, and since the flanges are not under any stress either, they will not get damaged. It would be best to establish standards for lifting and transporting the pipeline, so that contractors can follow those standards. Last edited by guaizilv on 2009-3-8 18:55.]
When transporting over long distances, there is a concern that the flange surfaces may be damaged. Additionally, since only one flange can be prefabricated in the factory while the other is welded on-site, there is a risk that something might be lost during transportation.
It is essential to know how to prefabricate a pipeline and what the appropriate prefabrication depth should be. Excellent plumbers handle this aspect very well; fittings can be connected to each other as well as to straight pipes during prefabrication, and there is no problem with that. However, it is necessary to take into account the conditions at the installation site and leave enough adjustment space. Otherwise, cuts may easily occur at the installation site.
It is better to include a straight pipe section; having a straight pipe section helps to stabilize the flow of the medium. Prefabrication is intended solely to reduce the amount of work on site, as construction in the prefabrication workshop is more convenient and faster, which facilitates processing and inspection and ensures construction quality.