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What is the minimum partial pressure of H2S that requires compliance with NACE MR0175?

What is the minimum partial pressure of H2S that requires compliance with NACE MR0175? What is the maximum ppm of H2S allowed without NACE MR0175?

NACE MR0175 is an international standard that provides the requirements for metallic materials exposed to H2S in oil and gas production environments. In NACE MR0175, the presence of H2S is quantified as the partial pressure of H2S. The material requirements, as well as environmental limits, are based on ppH2S. In this video the lower limit of ppH2S for NACE MR0175 compliance is discussed.

ANSI/NACE MR0175/ISO 15156 indicates that in production conditions with partial pressure of H2S (ppH2S) below 0.3kPa (0.05psi) no special precautions are required for carbon and low alloy steels. However highly susceptible carbon and low alloy steels (high strength, heavily cold worked etc) can still be susceptible to H2S related damage mechanisms even at ppH2S below these limits. Furthermore, the risk of Hydrogen Induced Cracking is present even at partial pressure of H2S (ppH2S) below 0.3kPa (0.05psi).

For corrosion resistant alloys (CRAs) there is now ppH2S low limit, which means precautions need to be taken whenever the possibility of H2S is present.

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