Valves used in oil and gas production may operate in environments containing hydrogen sulfide (H₂S). Under sour service conditions, unsuitable materials can be susceptible to cracking and premature failure.

NACE MR0175 / ISO 15156 provides requirements for selecting and qualifying metallic materials for H₂S-containing oil and gas production environments.

Why Is NACE Important for Valves?

NACE requirements mainly concern material selection and material condition, not simply valve pressure or leakage testing.

Depending on the valve design, important components may include:

• Valve body and bonnet
• Ball, gate, disc or plug
• Stem
• Bolting
• Weld overlays and hardfacing

Material grade, heat treatment and hardness can all affect a valve’s suitability for sour service.

Material and Hardness Requirements

For carbon and low-alloy steels, hardness control is particularly important because excessive hardness can increase the risk of sulfide stress cracking under certain H₂S conditions.

However, “NACE valve = maximum 22 HRC” should not be treated as a universal rule. Requirements depend on the specific material, heat treatment and service environment.

What Should Buyers Specify?

For a NACE valve order, buyers should provide:

1. H₂S concentration or partial pressure
2. Operating temperature and pressure
3. Required valve material
4. Applicable valve standard, such as API 6D
5. Inspection and documentation requirements

This information allows the manufacturer to properly evaluate material suitability and prepare the required documentation.

NACE MR0175 vs MR0103

NACE MR0175 / ISO 15156 is primarily intended for oil and gas production and related gas treatment environments.

NACE MR0103 / ISO 17945 is generally associated with petroleum refining and downstream sour-service applications.

The applicable standard should always be confirmed according to the actual service and project specification.

Conclusion

For sour-service valves, NACE compliance is more than simply marking a valve as “NACE.” Material grade, heat treatment, hardness and service conditions must be considered together.

Properly defining NACE requirements during the purchasing stage helps ensure suitable valve materials, reliable performance and complete technical documentation.