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V-1218 — Vacuum Gas Oil Drum V-1218

Alkylation Unit · Vacuum Gas Oil service · Installed Aug 24, 2016 (10 yrs in service)

High
Current Min. Thickness
0.398 in
t-min 0.405 in
Measured Corrosion Rate
15.71 mpy
ML-predicted: 14.61 mpy
Remaining Life
0.0 yrs
Next Inspection Due
Feb 20, 2027
Interval: 0.5 yrs (API 510)

UT Thickness Trend

Minimum CML reading per inspection vs. ASME Sec. VIII t-min

Vessel Specification

MaterialSA-387-11 Cl.2 (1.25Cr-0.5Mo)
Design CodeASME BPVC Section VIII, Div. 2
Joint Efficiency0.85
Design Pressure327 psig
Design Temperature579 °F
Operating Pressure261 psig
Operating Temperature468 °F
Diameter37 in
Nominal Thickness0.570 in
Corrosion Allowance0.1250 in
H2S / Chloride9 / 218 ppm
Flow Velocity12.5 ft/s
Process pH6.98
InsulatedNo

Corrosion & Remaining-Life What-If

Adjust operating conditions to see the live model-predicted corrosion rate and implied remaining life

Live Prediction — What-If Model
14.42 mpy
Predicted corrosion rate under these conditions (-1.29 mpy vs. current measured rate)
Implied Remaining Life
0.0 yrs
Implied Reinspection Interval
0.5 yrs

What-if model: standardized Ridge regression, R² 0.56 on held-out fleet data (3.25 mpy MAE). Runs entirely client-side for instant feedback — see Model Insights for the full fleet-scale ensemble model used for official predictions.

Governing Damage Mechanism — Naphthenic Acid Corrosion

API 571 §4.2.10

Aggressive, velocity-assisted corrosion in high-TAN crude fractions, most severe 450–750°F; low-alloy/carbon steel is far more susceptible than Mo-bearing or 316 SS.

Recommended inspection approach: UT thickness at high-velocity/turbulent locations; feed TAN monitoring; consider alloy upgrade per API 571 guidance.

Inspection History

UT thickness readings, most recent first

DateMethodCML CountAvg ThicknessMin CML Thickness
Aug 22, 2026UT Grid (API 572)40.4106 in0.3976 in
Jan 21, 2026UT Grid + RT40.4223 in0.4077 in
Oct 9, 2022UT Grid (API 572)40.4735 in0.4567 in
Mar 23, 2021UT Spot40.4961 in0.4819 in
Aug 3, 2018UT Grid + RT40.5371 in0.5272 in