Convert H2S concentration and total pressure into partial pressure, compare the 0.05 psi sour-service threshold, and prepare an ISO 15156 review.
Convert an H2S concentration and total pressure into H2S partial pressure, compare the result with the 0.05 psi sour-service screening threshold, and identify the inputs needed for an ISO 15156 review. The calculation does not select an alloy or approve a material for a specific stream.
Change the inputs to match the project. The result updates immediately and is not stored.
Use the H2S concentration in the gas phase and the total absolute pressure at the same point. For a liquid stream, use the gas in equilibrium with it.
Parts per million by volume.
Use absolute pressure, not gauge pressure.
Ideal-gas screen: p(H2S) = ppm x total pressure / 1,000,000. At high pressure or with a non-ideal gas, use the process simulation.
H2S partial pressure
0.725psi
0.05000 bar · 5.000 kPa
Screening result
At or above the 0.05 psi sour-service threshold
The threshold is a screening definition from NACE MR0175 / ISO 15156, not an alloy approval. pH, temperature, chloride and elemental sulfur still need assessment.
The partial pressure tells you whether the stream crosses the sour-service screening threshold. It does not tell you which alloy to buy.
Take the H2S concentration and total pressure from the same process case. If the stream is liquid, use the gas composition in equilibrium with the liquid.
Compare the result with 0.05 psi (0.35 kPa). A value at or above the threshold means the stream needs a sour-service assessment under NACE MR0175 / ISO 15156.
Complete the assessment with in-situ pH, chloride, temperature, elemental sulfur and the actual product form. The standard's material limits and environmental limits apply together.
Record the process case, H2S concentration, total pressure, partial pressure, pH basis, chloride, temperature and any test requirements. Keep the calculation with the material selection record so a later process change can be checked against the same assumptions.
NACE MR0175 / ISO 15156 uses a partial pressure of 0.05 psi (0.35 kPa) as the screening threshold for sour service. A stream at or above that value needs a sour-service assessment. The definition is a starting point, not an alloy approval: pH, temperature, chloride, elemental sulfur and other conditions can change the acceptable material and its limits.
No. ISO 15156-3 evaluates the material against the specific environment, including in-situ pH, H2S partial pressure, chloride concentration and temperature. It also distinguishes different product forms, heat treatments and hardness limits. Use this calculator to screen whether sour service applies, then complete the standard review with the operating envelope and any required laboratory testing.
For a gas mixture, multiply the H2S concentration in parts per million by volume by the total absolute pressure, then divide by one million. The result is the H2S partial pressure in the same pressure unit. At high pressure or with a non-ideal gas, use an equation of state or the project process simulation rather than the ideal-gas approximation.
Send the grade, dimensions, quantity, standard and inspection scope. Junda reviews the requirement and returns a technical quotation.