ASTM A105 Flange for Sour Service | NACE MR0175 / ISO 15156 Compliant
ASTM A105 sour service flanges are carbon steel forgings specifically manufactured for use in hydrogen sulfide (H₂S) environments. By controlling chemical composition, limiting hardness to ≤187 HBW, and applying strict quality control, these flanges meet NACE MR0175 / ISO 15156 requirements to resist sulfide stress cracking (SSC) and hydrogen-induced cracking (HIC) in oil and gas applications.
What is Sour Service?
Sour service refers to environments containing hydrogen sulfide (H₂S), commonly found in oil & gas production and refining systems.
Exposure to H₂S can cause:
- Sulfide Stress Cracking (SSC)
- Hydrogen-Induced Cracking (HIC)
- Stress Corrosion Cracking (SCC)
Materials must comply with NACE MR0175 / ISO 15156 to ensure safe operation.
NACE MR0175 / ISO 15156 Requirements
For ASTM A105 flanges, sour service compliance includes:
- Controlled chemical composition
- Reduced impurity levels (P, S)
- Maximum hardness ≤ 187 HBW
- Full traceability and testing
Hardness control is the most critical factor for SSC resistance.
Hardness Requirement
- Maximum hardness: 187 HBW
- Applies to all supply conditions (as-forged or heat-treated)
ASTM A105 standard already aligns with NACE hardness limits
Chemical Composition – ASTM A105 (%)
| Element | Requirement |
|---|---|
| C | ≤ 0.35 |
| Mn | 0.60 – 1.05 |
| Si | ≤ 0.35 |
| P | ≤ 0.040 (≤ 0.015 preferred for sour service) |
| S | ≤ 0.050 (≤ 0.010 preferred for sour service) |
Lower P & S improve resistance to HIC and SSC
Heat Treatment Requirements
ASTM A105 may be supplied:
- As-forged
- Normalized
- Normalized & tempered
Important Distinction:
- NACE MR0175:
✔ Accepts A105 if hardness ≤187 HBW - NACE MR0103 (Refinery standard):
✔ Requires mandatory heat treatment
Always confirm project specification
ASTM A105 with HIC Testing
For wet H₂S environments, additional testing may be required:
Standards:
- NACE TM0284
- ISO 15156
Evaluation Parameters:
- CLR (Crack Length Ratio)
- CTR (Crack Thickness Ratio)
- CSR (Crack Sensitivity Ratio)
Ensures resistance to hydrogen-induced damage
Product Types Available
We supply full range of A105 sour service flanges:
- Weld Neck Flange (WNRF)
- Slip-On Flange
- Blind Flange
- Threaded Flange
- Socket Weld Flange
- Lap Joint Flange
Standards:
- ASME B16.5
- ASME B16.47
Applications
ASTM A105 sour service flanges are widely used in:
- Oil & gas production systems
- Offshore platforms
- Refineries
- Gas processing units
- Pressure vessels
- Sour crude pipelines
Essential for H₂S and wet sour environments
Inspection & Testing
All flanges undergo strict quality control:
- Chemical analysis
- Hardness testing (100% if required)
- Ultrasonic testing (UT)
- Magnetic particle testing (MT)
- PMI testing
- Dimensional inspection
Certification:
- EN 10204 3.1 / 3.2
- Third-party inspection (SGS / BV / TUV)
Summary ASTM A105 NACE MR0175
- Material: ASTM A105
- Service: Sour (H₂S)
- Standard: NACE MR0175 / ISO 15156
- Hardness: ≤ 187 HBW
- Optional: HIC testing
- Application: Oil & gas, refinery
FAQ: ASTM A105 Sour Service Flanges
Q1: Can ASTM A105 be used for sour service?
Yes, if hardness is ≤187 HBW and chemical composition is controlled per NACE MR0175.
Q2: What is the maximum hardness for NACE compliance?
187 HBW.
Q3: Is heat treatment required?
Not always under MR0175, but required under MR0103.
Q4: What is HIC testing?
A test to evaluate resistance to hydrogen-induced cracking in wet H₂S environments.
Related Products:
ASTM A105 WNRF Flange NACE MR-0175
ASTM A105 flanges for sour service provide reliable performance in H₂S environments when manufactured in compliance with NACE MR0175 / ISO 15156. With controlled hardness, reduced impurity levels, and optional HIC testing, these flanges ensure safe and durable operation in critical oil and gas applications.
Contact us for project-specific technical support and competitive quotations.