What is NACE MR0175 intent when it comes to H₂S partial pressure? operating or design pressure to be used in the calculations?

Understanding Partial Pressure of H2S (ppH2S) for Carbon Steels, Low Alloy Steels, and Corrosion-Resistant Alloys

This page provides information on the partial pressure of H2S (ppH2S) used to set the production environment limits for carbon steels, low alloy steels, and corrosion-resistant alloys in ANSI/NACE MR0175/ISO 15156. However, NACE MR0175 does not specify whether the user should consider the operation pressure, design pressure, or an intermediate value. Thus, the page aims to provide clarity on whether the design or operating pressure should be used during the calculations involving the partial pressure of H2S.

Defining Partial Pressure of H2S

The page defines the partial pressure of H2S as the system total absolute pressure multiplied by the mol fraction of H2S present. The video on the page helps clarify whether to use the operating or design pressure when determining the partial pressure of H2S.

Assessing Risks and Consequences

The team at OGC Energy provides further assistance in determining the partial pressure of H2S by evaluating production conditions, the design, and assessing the risks and consequences.

Using ISO 15156-1 Para 6.1 to Determine Service Conditions

This page makes reference to a past inquiry sent to the NACE MR0175 maintenance panel about the partial pressure of H2S. The answer provided suggests that the user must define the service conditions that become the basis for calculating H2S partial pressure in accordance with ISO 15156-1 Para 6.1. It is up to the user to decide whether to use the operating or design pressure for partial pressure calculations.

By following these guidelines, you can ensure that you’re accurately calculating the partial pressure of H2S for your specific production environment, and minimizing the risk of damage to your equipment.

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