API RP 581 - 3rd Ed.2016 - Add.2-2020 - Risk-Based Inspection Methodology
2.B-56 API RECOMMENDED PRACTICE 5812.B.6.4ReferencesSee References [81], [82], [106], [107], [108], and [109] in Section 2.2.2.B.6.5 TablesTable 2.B.6.1—HF Corrosion—Basic Data Required for AnalysisBasic DataHF-in-water concentration (wt%)Material of constructionMaximum service temperature (°C:°F)Velocity (m/s:ft/s)Oxygen/oxidizers present? (Yes or No)CommentsDetermine the concentration of HF in the water.Determine the material used to fabricate the equipment/piping.Determine the maximum temperature of the process stream.Determine the velocity range of the process stream.Oxidizers can greatly accelerate corrosion of Alloy 400. No definition interms of concentration of dissolved oxygen in the acid can be given.Acid in shipment and transfer will usually be completely air-free, and airis typically present only after opening of equipment for inspection, leaks,or improperly prepared feed to the unit.
RISK-BASED INSPECTION METHODOLOGY, PART 2, ANNEX 2.B—DETERMINATION OF CORROSION RATES 2.B-57Table 2.B.6.2M—HF Corrosion—Estimated Corrosion Rates (mmpy) for Carbon SteelTemp. Velocity HF-in-Water Concentration (%)(°C) (m/s) 1 3 7 20 30 40 60 80 90 >9021.1-37.7854.4471.1187.78<1.524 0.76 2.54 7.62 17.78 20.32 17.78 3.81 0.51 0.20 0.05>1.524 1.52 5.08 15.24 25.37 25.37 25.37 7.62 1.02 0.38 0.10<1.524 2.54 8.89 25.37 25.37 25.37 25.37 12.70 1.27 0.64 0.18>1.524 5.08 17.78 25.37 25.37 25.37 25.37 25.37 2.54 1.27 0.38<1.524 10.16 25.37 25.37 25.37 25.37 25.37 25.37 6.35 2.54 0.64>1.524 20.32 25.37 25.37 25.37 25.37 25.37 25.37 12.70 5.08 1.27<1.524 25.37 25.37 25.37 25.37 25.37 25.37 25.37 25.37 10.16 2.54>1.524 25.37 25.37 25.37 25.37 25.37 25.37 25.37 25.37 20.32 5.08Table 2.B.6.3—HF Corrosion—Estimated Corrosion Rates (mpy) for Alloy 400Temp.(°F)Aerated?HF-in-Water Concentration (%)1 2 5 6 63 64 80 8180125175200No 1 1 1 10 10 1 1 2Yes 10 10 10 25 25 10 10 15No 1 1 1 15 15 5 5 3Yes 10 10 10 30 30 20 20 15No 5 5 5 20 20 10 10 5Yes 20 20 20 100 100 50 50 20No 10 10 10 20 20 20 20 10Yes 100 100 100 200 200 200 200 100Table 2.B.6.3M—HF Corrosion—Estimated Corrosion Rates (mm/y) for Alloy 400Temp(°C)Aerated?HF-in-Water Concentration (%)1 2 5 6 63 64 80 8127527993No 0.03 0.03 0.03 0.25 0.25 0.03 0.03 0.05Yes 0.25 0.25 0.25 0.64 0.64 0.25 0.25 0.38No 0.03 0.03 0.03 0.38 0.38 0.13 0.13 0.08Yes 0.25 0.25 0.25 0.76 0.76 0.51 0.51 0.38No 0.13 0.13 0.13 0.51 0.51 0.25 0.25 0.13Yes 0.51 0.51 0.51 2.54 2.54 1.27 1.27 0.51No 0.25 0.25 0.25 0.51 0.51 0.51 0.51 0.25Yes 2.54 2.54 2.54 5.08 5.08 5.08 5.08 2.54
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2.B-56 API RECOMMENDED PRACTICE 581
2.B.6.4
References
See References [81], [82], [106], [107], [108], and [109] in Section 2.2.
2.B.6.5 Tables
Table 2.B.6.1—HF Corrosion—Basic Data Required for Analysis
Basic Data
HF-in-water concentration (wt%)
Material of construction
Maximum service temperature (°C:°F)
Velocity (m/s:ft/s)
Oxygen/oxidizers present? (Yes or No)
Comments
Determine the concentration of HF in the water.
Determine the material used to fabricate the equipment/piping.
Determine the maximum temperature of the process stream.
Determine the velocity range of the process stream.
Oxidizers can greatly accelerate corrosion of Alloy 400. No definition in
terms of concentration of dissolved oxygen in the acid can be given.
Acid in shipment and transfer will usually be completely air-free, and air
is typically present only after opening of equipment for inspection, leaks,
or improperly prepared feed to the unit.
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