15CrMoH hydrogen sulfide resistant steel pipe flange

H₂S-resistant flanges are specially designed for sour service environments in oil & gas, petrochemical, and refining industries. These flanges resist sulfide stress cracking (SSC) and hydrogen-induced cracking (HIC) caused by exposure to wet H₂S, ensuring long-term safety and reliability.

Key Material Grades & Standards

Critical Requirements for H₂S Service:

✔ Hardness Control – Max 22 HRC (or 237 HB) to prevent SSC.
✔ Clean Steel Chemistry – Low sulfur (<0.002%) and phosphorus (<0.015%).
✔ HIC/SSCC Testing – Passes NACE TM0177 (Method A/B/D) and NACE TM0284.

Flange Types for Sour Service

1. Weld Neck (WN) – Best for high-pressure pipelines (e.g., wellheads).

2. Socket Weld (SW) – Compact, vibration-resistant for small-bore lines.

3. Blind Flange (BL) – Used to seal H₂S-containing pipelines.

4. RTJ (Ring-Type Joint) – Metal-to-metal seal for critical sealing.

Manufacturing & Quality Control

• Forged & Normalized – Improves grain structure for crack resistance.

• Soft Machining – Avoids work hardening (controlled tool speeds).

• Post-Weld Heat Treatment (PWHT) – Reduces residual stresses.

• 100% NDT – Ultrasonic (UT), magnetic particle (MT), or dye penetrant (PT) testing.

NACE & ISO Standards Compliance

• NACE MR0175/ISO 15156 – Cracking resistance in H₂S environments.

• NACE MR0103 – Resistance to SSC in refining environments.

• ISO 11960 (API 5CT) – For OCTG connections in sour wells.

Applications

• Sour Gas Pipelines – High-H₂S natural gas transport.

• Oil Refineries – Desulfurization units, amine treaters.

• Offshore Platforms – Subsea manifolds, wet gas systems.

• Geothermal Wells – H₂S-rich steam handling.