Vorschweißflansche gehören zu den am häufigsten verwendeten Flanschtypen in industriellen Rohrleitungssystemen. Anerkannt für ihre Langlebigkeit, Stärke, und Fähigkeit, mit Hochdruck- und Hochtemperaturbedingungen umzugehen, they are a top choice in industries like oil and gas, Petrochemie, Stromerzeugung, und Schiffbau.

This complete guide will cover everything you need to know about weld neck flanges, including their types, Abmessungen, Materialien, Vorteile, and common applications.

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What is a Weld Neck Flange?

A weld neck flange (WN-Flansch) is a type of flange with a long tapered hub and a smooth transition to the wall thickness of a pipe or fitting. It is designed to be butt-welded to the pipe, eine starke schaffen, leak-proof connection that can withstand high stress. The tapered hub also reduces stress concentration at the base of the flange.

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Key Features of Weld Neck Flanges

• Butt-Weld Connection: Ensures strength and minimizes stress at the joint.

• Tapered Hub: Provides reinforcement and smooth stress distribution.

• Bore Matching: The flange bore matches the pipe’s inner diameter for smooth fluid flow.

• High Integrity: Ideal for critical service conditions.

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Types of Weld Neck Flanges

1. Standard Weld Neck Flanges

• Commonly used in pipelines where pressure and temperature are high.

• Suitable for a wide range of applications.

2. Lange Vorschweißflansche

• Feature an extended hub, often used in equipment like nozzles or vessels.

• Provide additional reinforcement.

3. Reducing Weld Neck Flanges

• Used to connect pipes of different diameters.

• Maintain system integrity while accommodating size changes.

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Weld Neck Flange Dimensions

Weld neck flanges are manufactured according to international standards such as ASME B16.5, ASME B16.47, DIN, EN, und andere. Dimensions vary based on nominal pipe size (NPS), Druckklasse, and standard.

Key Dimensional Factors:

• Außendurchmesser (VON): Overall flange size.

• Bore Diameter: Matches the pipe ID.

• Hub Length: Length of the tapered section.

• Dicke: Affects pressure rating.

• Lochkreisdurchmesser: Distance between bolt holes.

Common Pressure Ratings:

• Klasse 150

• Klasse 300

• Klasse 600

• Klasse 900

• Klasse 1500

• Klasse 2500

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Materials Used for Weld Neck Flanges

The choice of material depends on operating temperature, Druck, und Flüssigkeitstyp.

Common Materials:

• Kohlenstoffstahl: ASTM A105, A350 LF2 (low-temp service)

• Edelstahl: ASTM A182 F304, F316

• Legierter Stahl: ASTM A182 F11, F22

• Duplex & Super-Duplex: UNS S31803, S32750

• Nickellegierungen: Inconel, Monel, Hastelloy

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Herstellungsprozess

1. Materialauswahl – Choose appropriate grade for service conditions.

2. Schmieden – The flange is shaped through forging for strength.

3. Bearbeitung – Precision machining ensures dimensional accuracy.

4. Wärmebehandlung – Relieves stress and enhances mechanical properties.

5. Inspektion & Testen – Includes dimensional checks, NDT, and pressure testing.

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Vorteile von Vorschweißflanschen

• Hohe Festigkeit: Butt-welded connection provides excellent structural integrity.

• Leak Resistance: Geeignet für Hochdruck- und Hochtemperaturanwendungen.

• Smooth Flow: Bore matching minimizes turbulence.

• Haltbarkeit: Long service life under extreme conditions.

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Nachteile

• Higher Cost: More expensive than slip-on or threaded flanges.

• Installation Time: Requires welding, which can be time-consuming.

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Applications of Weld Neck Flanges

1. Öl & Gaspipelines

Used in upstream, Mittelstrom, and downstream applications due to their strength and reliability.

2. Petrochemische Anlagen

Ideal for transporting chemicals under high pressure and temperature.

3. Stromerzeugung

Used in steam, Kühlwasser, and fuel systems.

4. Schiffbau & Off-Shore

Withstand harsh marine environments and high-pressure systems.

5. High-Temperature Services

Maintain integrity under extreme heat in refineries and chemical plants.

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Inspection and Quality Control

Weld neck flanges must undergo rigorous testing before being approved for service:

• Visuelle Inspektion: Checks for surface defects.

• Dimensional Verification: Ensures compliance with standards.

• Zerstörungsfreie Prüfung (NDT): Ultrasonic or radiographic testing for internal flaws.

• Hydrostatische Prüfung: Confirms pressure containment.

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Installation Guidelines

1. Ausrichtung: Ensure the pipe and flange bores align perfectly.

2. Schweißen: Perform butt-welding using approved procedures.

3. Bolt Tightening: Use a cross-pattern method for even gasket compression.

4. Dichtungsauswahl: Match gasket type to service conditions.

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Weld Neck vs Other Flange Types