1. How is the flange connected to the pipeline and where is it welded?
BS4504 101 Plate Flange manufacturers tell you that there are many types of flanges, generally flat flanges, butt welding flanges (long neck flanges), looper flanges, etc.

BS4504 101 Plate Flange manufacturers tell you that flat welding flanges are used for medium and low pressure, using plug welding, welding on both sides, the welding depth is 2-5mm from the flange sealing surface, butt welding flanges can be directly butt welding, loop flange bolts The connection does not require soldering.
2. What is a looper flange, where and what pipe fittings are looper flanges used for? BS4504 101 Plate Flange manufacturers tell you that the looper flange is the movable flange, which is generally matched to the water supply and drainage accessories (the most common on the expansion joint), and there is a flange at each end of the expansion joint when the manufacturer leaves the factory. , which are directly connected with the pipelines and equipment in the project with bolts.
The above information is the BS4504 101 Plate Flange manufacturer's introduction and analysis of the several types of the flange, hope it helps you.