Why sour service is different
In oil and gas plants, some lines carry H₂S.(Hydrogen Sulphide gas)
That changes everything.
H₂S may not always look dangerous from outside the pipe. But inside the valve, it can attack the metal slowly. It can create cracking that starts small and grows without warning.
This is why sour service valves need more than normal material selection.
They need proven compliance with NACE MR0175 / ISO 15156.
What can go wrong in sour service
The biggest risk is not only corrosion.
It is cracking.
H₂S can lead to Sulfide Stress Cracking, Hydrogen-Induced Cracking, and other hydrogen-related failures. These failures can happen when the wrong material, wrong hardness or wrong heat treatment is used.
A valve may pass pressure testing today. But if the metallurgy is not suitable, it can fail later in actual sour duty.
That is the real danger.
Why hardness limits matter
Harder is not always better.
In sour service, very high hardness can make metals more sensitive to cracking. This is why NACE MR0175 / ISO 15156 controls material hardness, heat treatment and condition of supply.
For many carbon and low-alloy steel applications, buyers often see limits such as maximum hardness requirements. The exact limit depends on material, service condition and standard requirement.
The point is simple.
The supplier must prove that the valve is not only strong, but also resistant to cracking in H₂S service.
Material and trim selection must match the duty
Sour service valve selection includes body material, trim material, bolting, weld overlays, seats, stem and internal parts.
Every part exposed to the media matters.
The material must match pressure, temperature, H₂S level, chloride content, pH, and other service details. Trim selection also matters because seats and stems face stress, movement, and sealing load.
A wrong trim can become the weak link.
What the supplier must prove in the MDR
For sour service, verbal assurance is not enough.
The MDR should include material test certificates, heat numbers, hardness test records, NACE compliance statements, heat treatment records, welding documents where applicable, NDE reports, hydro and seat test reports and full traceability.
This gives the buyer a clear evidence trail.
It also helps during audits, shutdowns, inspections and future maintenance.
How IPC helps buyers reduce risk
IPC studies the service conditions before recommending sour service valves.
We check the media, pressure, temperature, material requirement, trim selection, hardness control and documentation expectation.
The aim is simple.
Prevent SSC and HIC failures. Improve safety. Support reliable oil and gas operation.
For sour service applications, IPC supplies valves with the right material approach and the documentation buyers need to prove compliance.