PPM · Grains/100cf · Sulfur Loading
Learn H2S concentration conversions, toxicity levels, and NACE MR0175 requirements
H₂S in ppmv is converted to grains per 100 scf using the molecular weight relationship and standard gas density. The conversion factor is approximately 1 grain/100 scf = 15.9 ppmv, based on GPSA standard conditions (60°F, 14.696 psia). This is essential for pipeline tariff gas quality specifications.
NACE MR0175/ISO 15156 defines sour service when the H₂S partial pressure exceeds 0.05 psia (0.3 kPa) in gas systems. This threshold determines material selection requirements for pressure-containing equipment to prevent sulfide stress cracking.
Pipeline quality natural gas typically requires H₂S below 4 ppmv (0.25 grains/100 scf) per most US pipeline tariffs. Some specifications allow up to 16 ppmv (1 grain/100 scf). These limits protect pipeline integrity and downstream equipment from sulfide corrosion.
H₂S partial pressure equals the mole fraction (ppmv divided by 1,000,000) multiplied by the total absolute pressure. For example, 100 ppmv H₂S at 1,000 psia total pressure yields an H₂S partial pressure of 0.1 psia.