Recommended to make a company own standard for equipment in sour service. Most of the companies have severity categories for HIC for selection of HIC resistant steel in sour services based on partial pressure, normal operating pressure, thickness, H2S wet%, pH, %CN,etc.
The following requirements in materials & its fabrication procedure of equipment are most stringent as under.
- Vacuum Degassing Treatment
- Fully killed fine grain practice (>ASTM No.7 for vessels)
- Tempering temp for Q-T/ N-T steels; min 650 deg. C
- Max Y.S for piping: 8000psi (SA-516-55 / 60 preferred)
- Metallic inclusion shape controlled required. TMCP steel rolled at 1300 to 1650 deg. F not recommended.
- S<=0.002%, P<=0.010%, Ceq ; max 0.22% for t<=1/2", max 0.24% for 1/2"<t<=2", max 0.26% for t>2"
- Ca treatment
- Tempering temperature for Q-T or N-T steels; min 650C
- UT for steel: SA-578 Level S1-100% scanning.
- HIC Test
(1)Test time: 96 hours
(2)Test Procedure-NACE TM0284/ pH;at Design condition or 3 (TM0177)
(3) Acceptable Criteria;
- 100% PWHT ; Required
- Hardness <=200 BHN on weldments& HAZ
- RT : Full
- 100% with WFMPI on weldments and HAZ.