Weld neck flanges are resistant to deformation, provide good sealing, and have wide applications. They meet the requirements for both rigidity and elasticity and feature a reasonable transition for weld thinning. The weld joint is far from the mating surface, thus preventing deformation due to welding temperatures. They utilize a more complex trumpet-shaped structure, suitable for pipelines subject to significant fluctuations in pressure or temperature, as well as for high-temperature, high-pressure, and low-temperature pipelines. Generally used for pipeline and valve connections with PN greater than 2.5 MPa; also used on pipelines transporting expensive, flammable, or explosive media.