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V-1350 — Sour Gas Overhead Vessel V-1350

Alkylation Unit · Sour Gas Overhead service · Installed Sep 1, 1987 (39 yrs in service)

Medium
Current Min. Thickness
0.906 in
t-min 0.739 in
Measured Corrosion Rate
0.50 mpy
ML-predicted: 1.24 mpy
Remaining Life
60+ yrs
Next Inspection Due
Aug 19, 2036
Interval: 10.0 yrs (API 510)

UT Thickness Trend

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

Vessel Specification

MaterialSA-516-70 Carbon Steel
Design CodeASME BPVC Section VIII, Div. 2
Joint Efficiency0.85
Design Pressure233 psig
Design Temperature530 °F
Operating Pressure201 psig
Operating Temperature403 °F
Diameter104 in
Nominal Thickness0.938 in
Corrosion Allowance0.1250 in
H2S / Chloride1457 / 35 ppm
Flow Velocity9.7 ft/s
Process pH5.26
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
0.10 mpy
Predicted corrosion rate under these conditions (-0.40 mpy vs. current measured rate)
Implied Remaining Life
60+ yrs
Implied Reinspection Interval
10.0 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 — Wet H2S Damage (SSC/HIC)

API 571 §4.5.1

Hydrogen-induced cracking (HIC) and sulfide stress cracking (SSC) in carbon/low-alloy steel exposed to wet H2S service. Not detectable by thickness monitoring alone.

Recommended inspection approach: Wet fluorescent magnetic particle (WFMT) and UT shear-wave/AUBT surveys in addition to routine UT thickness, per API RP 571 and NACE SP0296.

This mechanism is crack-dominant — thickness monitoring alone will not detect it. See Standards & Documentation for the full NDE requirement.

Inspection History

UT thickness readings, most recent first

DateMethodCML CountAvg ThicknessMin CML Thickness
Aug 22, 2026UT Grid + RT60.9231 in0.9057 in
Jan 11, 2026UT Grid + RT60.9269 in0.9222 in
May 20, 2024UT Grid (API 572)60.9254 in0.9154 in
Oct 21, 2022UT Grid (API 572)60.9284 in0.9100 in
Aug 27, 2020UT Spot60.9226 in0.9095 in
Apr 7, 2018UT Spot60.9286 in0.9136 in
Feb 16, 2016UT Grid + RT60.9310 in0.9235 in
Jun 23, 2014UT Spot60.9304 in0.9223 in
Aug 24, 2012UT Spot60.9337 in0.9158 in
Jan 25, 2010UT Grid (API 572)60.9320 in0.9130 in
Jul 22, 2008UT Grid + RT60.9334 in0.9298 in
Apr 30, 2006UT Grid (API 572)60.9294 in0.9095 in
Nov 11, 2003UT Grid (API 572)60.9367 in0.9234 in
Aug 26, 2001UT Grid + RT60.9349 in0.9324 in
Jun 2, 1998UT Grid + RT60.9304 in0.9300 in
Jul 10, 1996UT Grid + RT60.9324 in0.9221 in
Dec 15, 1994UT Grid (API 572)60.9348 in0.9224 in
Jun 7, 1993UT Grid (API 572)60.9364 in0.9253 in
Jun 16, 1990UT Grid + RT60.9340 in0.9151 in