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V-1029 — Sour Gas Overhead Vessel V-1029

Alkylation Unit · Sour Gas Overhead service · Installed Aug 29, 1998 (28 yrs in service)

Medium
Current Min. Thickness
2.083 in
t-min 2.061 in
Measured Corrosion Rate
2.31 mpy
ML-predicted: 2.38 mpy
Remaining Life
9.5 yrs
Next Inspection Due
May 16, 2031
Interval: 4.7 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 Pressure505 psig
Design Temperature433 °F
Operating Pressure325 psig
Operating Temperature316 °F
Diameter121 in
Nominal Thickness2.164 in
Corrosion Allowance0.0625 in
H2S / Chloride509 / 144 ppm
Flow Velocity19.0 ft/s
Process pH7.30
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
3.74 mpy
Predicted corrosion rate under these conditions (+1.43 mpy vs. current measured rate)
Implied Remaining Life
5.9 yrs
Implied Reinspection Interval
2.9 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 + RT82.0949 in2.0825 in
Mar 30, 2026UT Grid + RT82.1025 in2.0907 in
Mar 2, 2024UT Grid (API 572)82.1069 in2.0948 in
Nov 27, 2020UT Spot82.1145 in2.0952 in
Nov 11, 2017UT Spot82.1234 in2.1061 in
Sep 22, 2014UT Grid (API 572)82.1283 in2.1087 in
Apr 1, 2012UT Grid (API 572)82.1333 in2.1263 in
Nov 14, 2010UT Grid + RT82.1367 in2.1327 in
Sep 13, 2007UT Grid (API 572)82.1426 in2.1226 in
Mar 10, 2006UT Spot82.1477 in2.1464 in
Oct 23, 2003UT Grid + RT82.1556 in2.1413 in
Dec 24, 2000UT Grid (API 572)82.1576 in2.1408 in