NACE MR0175 Sour Service Weld Neck Flange

The NACE MR0175 Sour Service Weld Neck Flange is purpose-built for oil and gas pipeline systems that transport hydrogen sulfide (H2S) and other aggressive sour media. Manufactured from fully killed carbon steel and low-alloy grades that comply with NACE MR0175 / ISO 15156, this weld neck flange offers dependable resistance to sulfide stress cracking (SSC) and hydrogen-induced cracking (HIC) in the most demanding wellhead, gathering and processing environments.

Each sour service weld neck flange is produced through closed-die forging, followed by normalizing, quenching and tempering heat treatment to achieve uniform grain structure and controlled hardness. The raised face weld neck hub forms a smooth, continuous transition into the pipe bore, reducing turbulence and stress concentration at the weld joint. This high-integrity design is trusted across sour gas fields, transmission pipelines and refinery applications where H2S concentrations require certified sour service material.

Product Specifications

Key Advantages

• Full compliance with NACE MR0175 / ISO 15156 for sour gas service
• Resistant to sulfide stress cracking and hydrogen-induced cracking
• Normalized and tempered heat treatment for uniform mechanical properties
• Forged construction delivers superior grain structure and strength
• Complete material traceability with EN 10204 3.1 mill test certificates
• Third-party inspection available from SGS, BV, TUV and DNV
• Controlled hardness to meet sour service requirements
• Suitable for wellhead equipment and gathering line connections

Frequently Asked Questions

Q: What does NACE MR0175 compliance mean for a weld neck flange?

A: NACE MR0175 / ISO 15156 is the international standard governing materials used in oil and gas environments containing hydrogen sulfide. A compliant weld neck flange is made from approved materials with controlled hardness and heat treatment, ensuring it resists sulfide stress cracking when exposed to sour service conditions.

Q: Which materials are suitable for sour service weld neck flanges?

A: Common sour service materials include ASTM A105 carbon steel with controlled hardness, ASTM A350 LF2 for low-temperature applications, and ASTM A694 F42 through F70 grades for high-pressure transmission pipelines. The correct grade depends on H2S concentration, temperature and pressure of the specific application.

Q: Do you provide material test certificates for sour service flanges?

A: Yes, every sour service weld neck flange is supplied with full EN 10204 3.1 mill test certificates covering chemical composition, mechanical properties, hardness testing and NACE compliance documentation.

Manufacturing & Quality Control

Our sour service weld neck flanges are forged in-house and subjected to rigorous quality control at every production stage. Each heat is verified by spectrometric chemical analysis, and every finished flange undergoes hardness testing, ultrasonic inspection and dimensional verification before release. Controlled hardness values and complete material traceability give operators confidence that each sour service flange will perform reliably in H2S environments throughout its service life.

Q: What testing is performed on sour service flanges before shipment?

A: Beyond standard dimensional and visual inspection, we perform hardness testing within NACE MR0175 limits, ultrasonic testing for internal defects and positive material identification. Complete inspection reports are supplied with every shipment for your quality records.