ASTM A105 Flange for Sour Service – NACE MR0175 / ISO 15156 Compliant

ASTM A105 flanges for sour service are specially manufactured carbon steel forgings designed for use in hydrogen sulfide (H₂S) containing environments. These flanges are produced with controlled chemical composition, hardness limitations, and strict quality procedures to comply with NACE MR0175 / ISO 15156 requirements.

They are widely used in oil and gas production, refineries, and gas processing facilities where resistance to sulfide stress cracking (SSC) and hydrogen-induced cracking (HIC) is critical.

What is Sour Service?

Sour service refers to environments containing hydrogen sulfide (H₂S), commonly encountered in oil and gas production and refining operations.

Exposure to H₂S may lead to:

• Sulfide Stress Cracking (SSC)

• Hydrogen-Induced Cracking (HIC)

• Stress Corrosion Cracking (SCC)

To prevent material failure, metallic components must comply with NACE MR0175 / ISO 15156 requirements.

NACE MR0175 / ISO 15156 Compliance

NACE (National Association of Corrosion Engineers) publishes standards governing material performance in H₂S environments. NACE MR0175 / ISO 15156 defines requirements for metallic materials used in oil and gas production.

For carbon steel materials such as ASTM A105, compliance typically involves:

• Controlled chemical composition

• Maximum hardness ≤ 187 HBW

• Proper manufacturing practices

• Full material traceability

Hardness testing is performed to verify compliance.

Chemical Composition – ASTM A105 (Typical %)

For NACE MR0175 compliance, project specifications commonly require reduced phosphorus and sulfur levels to improve HIC resistance.

Hardness Requirement for NACE MR0175

To comply with NACE MR0175:

• Maximum hardness must not exceed 187 HBW

This requirement applies regardless of whether the forging is supplied in the as-forged or heat-treated condition.

ASTM A105 itself permits a maximum hardness of 187 HBW, which aligns with NACE MR0175 limits.

Heat Treatment Requirements

ASTM A105 flanges may be supplied in the as-hot-forged condition unless otherwise specified.

For larger sizes (e.g., greater than NPS 4) or higher pressure classes (Class 300 and above), normalization is commonly required.

Important clarification:

• NACE MR0175 allows ASTM A105 forgings provided hardness requirements are met.

• NACE MR0103 (refinery standard) does not automatically waive heat treatment requirements.

• Under MR0103, material must be heat treated by annealing, normalizing, normalizing & tempering, or quenching & tempering.

Therefore, if MR0103 compliance is required, additional heat treatment verification is necessary.

ASTM A105 with HIC Testing

For wet H₂S service, ASTM A105 flanges can be supplied with Hydrogen-Induced Cracking (HIC) testing according to:

• NACE TM0284

• NACE MR0175 / ISO 15156

• Project-specific oil & gas specifications

HIC evaluation includes:

• Crack Length Ratio (CLR)

• Crack Thickness Ratio (CTR)

• Crack Sensitivity Ratio (CSR)

Testing is performed on representative samples from the same heat to ensure material integrity.

Product Types Available

We supply ASTM A105 sour service flanges in:

• Welding Neck Flange

• Slip-On Flange

• Blind Flange

• Threaded Flange

• Socket Weld Flange

• Lap Joint Flange

Manufactured according to:

• ASME B16.5

• ASME B16.47

Applications

ASTM A105 sour service flanges are widely used in:

• Oil & gas production systems

• Offshore platforms

• Refinery piping

• Pressure vessels

• Gas processing units

• Sour crude pipelines

They are essential components in wet H₂S environments where hydrogen damage is a risk.

Testing & Inspection

All sour service flanges undergo:

• Chemical analysis

• Hardness testing (100% if required)

• Ultrasonic testing (UT)

• Magnetic particle inspection (MT)

• PMI testing

• Dimensional inspection

Material Test Certificate EN 10204 3.1 / 3.2 available upon request.
Third-party inspection (SGS, BV, TUV) supported.

Related Products:

ASTM A105 Weld neck Flanges

ASTM A105 WNRF Flange NACE MR-0175

ASTM A105 BLIND FLANGES

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.