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06General useH 2 S utilization limits for different stainless steel familiesGeneral UsePREN: the Pitting Resistance EquivalentNumber is developed to reflect and predictthe pitting resistance of Corrosion ResistantAlloys (CRA) in the presence of dissolvedchloride. It’s based upon the proportions ofCr, Mo, W, N in the composition of the alloy.T°C232200150DUPLEXPREN 30 - 40DUPLEXPREN > 40 Ni ALLOY Ni Co KC35N 1201007050200MARTENSITICpH > 3,5AUSTENITIC UGI 209AUSTENITICNo Chloride concentration limitSUPER AUSTENITICChloride < 5000 mg/lAUSTENITICChloride < 50 mg/lPartialpressure(psi)0,1 0,2 0,3 0,5 0,8 1 1,5 2 3 5 8 10 15 20 30 50 80 100 -> pH 2S3 10 25 50 250 500 -> pCO 2Domain of use of the stainless and alloys grades concerning the Oil and Gas market,depending to the temperature, to the partial pressure of H 2 S and CO 2Martensitic gradesMartensitics are limited to pH higher than3,5 and in some exceptions higher than4,5 (wellhead, Xmas trees, etc.)Austenitic gradesAustenitics are limited in temperature(up to 50 °C). They can be used up to15 psia with no chloride concentration limit,or even until up to 50 psia H 2 S in casethe Cl-concentration is less than 50 mg/l.One exception is the UGI 209, which has alittle higher temperature limit (up to 66 °C)for use in any equipment or components.Moreover this grade has almost twicehigher mechanical properties than the otheraustenititic grades.Duplex gradesThey should not be used at temperatureshigher than 232 °C. These grades are dividedinto two sections: those with a PRENbetween 30 and 40 (45N) are limited in H 2 Spressure up to 1.5 psia, those with a higherPREN (52N+) can be used up to 3 psia.Super austenitic gradesThe highest partial pressure of H2S canwithstand the superaustentitic grades. Theutilization limits depends on temperature;the higher the temperature, the lower thepH 2 S limit. The 1.4529 is cited as an individualalloy and shall be used up to 121 °C,up to 100 psia H 2 S with 60 700 mg/lchloride if the pH is higher than 3.5.NB: The previous information provided is for indicative purpose only.