WN high-neck butt-weld flange (WN flange) is the core connecting component in the pipeline system for high pressure, high temperature and harsh working conditions. Its characteristics are that the neck of the flange (Neck) extends long and is connected to the pipe by butt welding. It forms a smooth transition with the pipe through the neck, significantly reducing stress concentration. It is suitable for severe vibration, temperature fluctuations or high pressure differential environments. It is the preferred flange type in the petroleum, chemical industry, electricity and other industries.
Model and standard
Common criteria:
National Standard (GB/T 9115): WN series, pressure range PN10~PN160.
American Standard (ANSI B16.5/ASME B16.47): Class 150~Class 2500.
European Standard (EN 1092-1): Type 11 (butt-welded flange).
Daily standard (JIS B2220): 5K~63K.
Model example:
WN PN100 DN300: represents the national standard butt welding flange, nominal pressure PN100, diameter DN300.
Core features
High-strength structural design
Long neck transition: The flange neck is connected to the pipe butt welding, and the weld is away from the flange sealing surface, reducing the influence of thermal stress on sealing performance.
Strong fatigue resistance: suitable for frequent thermal cycles (such as steam pipes) or mechanical vibration scenarios (such as compressor outlets).
Ultra-high pressure load bearing capacity
It can cover PN10~PN160 (national standard) or Class 150~Class 2500 (US standard), far exceeding flat-welded flange (SO) and neck-welded flange (SO-Hub).
Excellent sealing performance
The sealing surface has various forms: protruding surface (RF), ring connection surface (RTJ), concave and convex surface (MFM), suitable for high-precision sealing components such as metal ring pads and octagonal pads.
Sealing surface surfacing stainless steel (Stellite 6) or cemented carbide, high temperature resistance (up to 800℃) and corrosive media.
Wide material adaptability
Conventional materials: carbon steel (A105), stainless steel (304/316L), low temperature steel (LF2).
Very small flow resistance
The inner diameter of the flange is consistent with the inner diameter of the pipe, the medium flows without throttling, reducing pressure drop, and is suitable for high flow velocity or easy crystallization fluid.
Technical parameters
Project Parameter Description
Nominal diameter DN15~DN2000 (supports non-standard customization)
Nominal pressure PN10~PN160 / Class150~Class2500
Applicable temperature -196℃ (deep cooling) ~ +800℃ (high temperature alloy)
Valve body material: Carbon steel, stainless steel, alloy steel, special metal
Sealing surface RF (protrusion), RTJ (ring groove surface), MFM (concave and convex surface)
Connection standards GB, ANSI, EN, JIS, DIN, etc.
Application areas
Oil and gas mining: subsea pipelines, high-pressure wellhead devices.
Refining and chemical device: hydrogenation reactor, high-temperature cracking pipeline.
Nuclear power system: main steam pipeline, containment through-piece.
Liquefied natural gas (LNG): -162℃ ultra-low temperature storage and transportation pipeline.
Aerospace: Liquid oxygen and liquid hydrogen delivery systems.
Selection and installation guide
Key points for selection:
High pressure/high temperature preferred: Forced use of WN flanges when pressure ≥ PN40 or temperature ≥300℃.
Media characteristics: It is recommended to choose an RTJ sealing surface (metal ring pad has strong extrusion resistance).
Low temperature and deep cooling: choose austenitic stainless steel (304L) or nickel-based alloy to avoid low temperature brittle cracking.
Welding specifications:
The end of the pipe needs to be processed with bevel (V-shaped or U-shaped) and accurately butt-welded with the flange neck.
After welding, 100% ray detection (RT) and hardness test are required to ensure that the weld is free of cracks and pores.
Maintenance suggestions:
Regularly check the wear of the sealing surface, and the thermal relaxation of the bolts must be monitored for high-temperature working conditions (it is recommended to use a disc spring gasket).
Avoid knocking on the flange sealing surface during disassembly to prevent deformation and leakage.