P91 Alloy Steel Welding Neck Flanges According To ASME B16.47

Large-diameter welding neck flanges are butt-welded connection flanges with a nominal diameter above DN450 and a round pipe transition neck, primarily used in pipeline systems under harsh conditions such as severe pressure fluctuations, high temperature and high pressure, low temperature, or the transportation of flammable and explosive media.
This flange includes international standard specifications such as ASME B16.5, ASME B16.47, and DIN 2631 series. It employs a double-sided welding process to ensure sealing reliability. Compared to slip-on flanges, its butt-welded structure offers higher nominal pressure resistance (approximately 16 MPa) and is suitable for hazardous medium transportation in industries like petrochemicals. However, its manufacturing cost is higher than that of single-sided welded slip-on flanges

1. Different scope of application:SO flanges are suitable for connecting carbon steel pipes with a nominal pressure not exceeding 2.5MPa. The sealing surface of SO flanges can be made into three types: smooth, concave convex, and mortise and tenon groove. Smooth SO flanges are widely used in situations where the medium conditions are relatively mild, such as low-pressure non purified compressed air and low-pressure circulating water. Welding Neck flanges are used on pipelines that transport expensive, flammable, and explosive media. Welding Neck flanges are not easily deformed, have good sealing, and are widely used. The nominal pressure PN is around 16MPa.
2. Different welding methods: When welding Slip on flanges, only single-sided welding is required, and there is no need to weld the inner port of the pipeline and flange connection; The welding installation of Welding Neck flanges requires double-sided welding of the flanges. So the use of Welding Neck is to reduce stress concentration. Generally, Welding Neck flanges are mostly neck flanges, also known as nipple flanges.
3. Different prices: Slip On flanges are relatively cheaper; However, due to the additional process, the installation cost, labor cost, and auxiliary material cost of Welding Neck are higher, and the price is relatively more expensive.