NACE MR0175 Fasteners for Sour Service
Select and document stud bolts and heavy hex nuts for H₂S-containing environments with a project-specific review of material, hardness, temperature and service limits.
NACE MR0175 / ISO 15156 selection is not just a product-name claim. Confirm the material condition, maximum hardness, temperature, environment and applicable equipment category against the project specification. B7M, L7M and compatible modified nut grades may be selected where the service requirements call for reduced hardness and sour-service controls.
Specification and supply scope
| Common grades | ASTM A193 B7M/L7M and compatible ASTM A194 modified grades such as 2HM or 7M, subject to the service specification. |
|---|---|
| Key control | Material condition and hardness must be verified against the applicable NACE/ISO 15156 environmental limits. |
| Service review | Consider H₂S partial pressure, temperature, chloride exposure, pH, tensile stress and equipment category before release. |
| Records | Heat traceability, chemical analysis, mechanical properties, hardness results and a project-specific compliance statement. |
| Important limitation | NACE compliance is conditional on the actual material, heat treatment, dimensions and service environment; it is not inferred from the grade name alone. |
Typical applications
- ✓Sour-gas and oil production equipment
- ✓Refinery and petrochemical process piping
- ✓Wellhead, valve and flange assemblies
- ✓EPC projects requiring ISO 15156 documentation
Documentation available
- ✓Heat and lot traceability
- ✓Hardness and mechanical test records
- ✓NACE MR0175 / ISO 15156 compliance statement
- ✓Coating, PMI and third-party inspection records when specified
Related engineering resources
Need a grade, drawing or complete bolting set?
Send the standard, size, quantity, coating and service condition. LOKRON's technical sales team can confirm scope and documentation within 24 hours.
Request a technical quoteFrequently asked questions
Does ASTM A193 B7 automatically meet NACE MR0175?
No. Sour-service suitability depends on the applicable material condition, hardness, dimensions and environmental limits. A modified grade such as B7M may be required by the project specification.
What documents should be requested for NACE fasteners?
Request the heat-linked MTR, hardness results, mechanical test results and a compliance statement referencing the applicable NACE MR0175 / ISO 15156 requirements.
Can LOKRON review a customer sour-service specification?
Yes. Provide the equipment standard, H₂S conditions, temperature, grade, size, coating and required documentation so the material selection can be reviewed before quotation.