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V-1080 — Atmospheric Gas Oil Column V-1080

Alkylation Unit · Atmospheric Gas Oil service · Installed Sep 1, 1984 (42 yrs in service)

High
Current Min. Thickness
0.527 in
t-min 1.090 in
Measured Corrosion Rate
16.93 mpy
ML-predicted: 16.27 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. 1
Joint Efficiency1.00
Design Pressure328 psig
Design Temperature737 °F
Operating Pressure195 psig
Operating Temperature491 °F
Diameter117 in
Nominal Thickness1.211 in
Corrosion Allowance0.0938 in
H2S / Chloride43 / 103 ppm
Flow Velocity10.4 ft/s
Process pH4.33
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
13.52 mpy
Predicted corrosion rate under these conditions (-3.41 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 + RT80.5450 in0.5272 in
Jun 14, 2026UT Spot80.5450 in0.5360 in
Mar 6, 2024UT Grid (API 572)80.5450 in0.5374 in
Dec 31, 2020UT Grid + RT80.5450 in0.5318 in
Oct 4, 2017UT Grid (API 572)80.5450 in0.5376 in
Dec 7, 2015UT Spot80.5450 in0.5301 in
Jun 17, 2013UT Grid + RT80.5568 in0.5420 in
Apr 6, 2011UT Grid + RT80.6057 in0.5884 in
Jul 4, 2009UT Grid (API 572)80.6445 in0.6352 in
Aug 29, 2007UT Grid (API 572)80.6863 in0.6688 in
Feb 16, 2005UT Spot80.7475 in0.7467 in
Dec 20, 2002UT Grid (API 572)80.7949 in0.7807 in
Jan 22, 2000UT Spot80.8620 in0.8611 in
Dec 28, 1996UT Spot80.9301 in0.9188 in
Jan 3, 1994UT Spot80.9978 in0.9944 in
Feb 18, 1991UT Grid + RT81.0652 in1.0541 in
Aug 11, 1989UT Spot81.1010 in1.0963 in
Mar 1, 1987UT Grid + RT81.1553 in1.1373 in