NACE MR0175 / ISO 15156 — Sour Service Valve Material Selection
NACE MR0175 (aligned with ISO 15156) restricts materials and hardness for H2S-containing (sour) environments. Writing “NACE” alone is incomplete — state applicable parts and design conditions.
Quick selection
Collect H2S partial pressure, chloride, pH, temperature, then select compliant body/trim/bolting with hardness control.
Comparison table
| Factor | What to specify | What “NACE” alone misses |
|---|---|---|
| Environment | H2S, chlorides, temp, pH | Unstated sour severity |
| Materials | Compliant alloys / hardness limits | Generic SS without hardness notes |
| Docs | MTC + NACE compliance statement | Commercial invoice only |
| Valve scope | Body, trim, bolting, stems | Body-only claims |
| Buyer action | Design conditions + compliance ask | Checkbox without data |
Practical RFQ notes
Sour service often pairs with fire-safe, FE packing, and RTJ ends — confirm each separately.
- Bolting and stems are frequent non-compliance points.
- Cladding / overlays may be used — state explicitly.
RFQ wording that works
- “Ball / gate / check for sour service per NACE MR0175 / ISO 15156, H2S __, temperature __, hardness-controlled trim, MTC 3.1.”
FAQ
Is MR0175 the same as ISO 15156?
They are aligned sour-service materials documents. Cite the edition in use.
Does NACE apply to water valves?
Only if service is defined as sour per the standard.
Can soft seats be used in sour service?
Elastomer compatibility matters — confirm with materials engineering.
Is Duplex always required?
Not always. Follow ISO 15156 / project metallurgy.
Related RFQs and hubs
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