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V-1258 — Vacuum Resid Vessel V-1258

Delayed Coker · Vacuum Resid service · Installed Aug 26, 2009 (17 yrs in service)

Low-Medium
Current Min. Thickness
2.153 in
t-min 2.096 in
Measured Corrosion Rate
5.87 mpy
ML-predicted: 6.55 mpy
Remaining Life
9.7 yrs
Next Inspection Due
Jun 25, 2031
Interval: 4.8 yrs (API 510)

UT Thickness Trend

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

Vessel Specification

MaterialSA-240 Duplex 2205
Design CodeASME BPVC Section VIII, Div. 1
Joint Efficiency0.85
Design Pressure634 psig
Design Temperature102 °F
Operating Pressure361 psig
Operating Temperature63 °F
Diameter138 in
Nominal Thickness2.256 in
Corrosion Allowance0.1250 in
H2S / Chloride46 / 163 ppm
Flow Velocity4.4 ft/s
Process pH8.08
InsulatedYes

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
7.06 mpy
Predicted corrosion rate under these conditions (+1.19 mpy vs. current measured rate)
Implied Remaining Life
8.1 yrs
Implied Reinspection Interval
4.0 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 — High-Temperature Sulfidation

API 571 §4.2.11

Reaction of sulfur compounds with steel at high temperature (>500°F) in the absence of water; rate governed by sulfur content, temperature, alloy content.

Recommended inspection approach: UT thickness per Modified McConomy-curve risk ranking; RT/UT at known high-rate locations identified by process simulation.

Inspection History

UT thickness readings, most recent first

DateMethodCML CountAvg ThicknessMin CML Thickness
Aug 22, 2026UT Spot62.1575 in2.1531 in
Oct 18, 2024UT Spot62.1704 in2.1539 in
Jun 14, 2022UT Spot62.1802 in2.1623 in
Oct 25, 2019UT Spot62.1992 in2.1957 in
Dec 9, 2017UT Grid (API 572)62.2082 in2.2075 in
Sep 29, 2015UT Spot62.2253 in2.2249 in
May 5, 2014UT Grid + RT62.2301 in2.2106 in
Sep 3, 2011UT Grid + RT62.2470 in2.2422 in