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V-1014 — Wet H2S Gas Drum V-1014

Alkylation Unit · Wet H2S Gas service · Installed Aug 25, 2012 (14 yrs in service)

Medium
Current Min. Thickness
0.939 in
t-min 0.847 in
Measured Corrosion Rate
2.00 mpy
ML-predicted: 3.71 mpy
Remaining Life
46.3 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-240-304L Stainless
Design CodeASME BPVC Section VIII, Div. 2
Joint Efficiency0.85
Design Pressure429 psig
Design Temperature365 °F
Operating Pressure328 psig
Operating Temperature278 °F
Diameter55 in
Nominal Thickness0.986 in
Corrosion Allowance0.0625 in
H2S / Chloride282 / 239 ppm
Flow Velocity6.9 ft/s
Process pH4.54
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
6.19 mpy
Predicted corrosion rate under these conditions (+4.19 mpy vs. current measured rate)
Implied Remaining Life
14.9 yrs
Implied Reinspection Interval
7.5 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 — 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 Spot40.9559 in0.9389 in
Mar 14, 2025UT Grid + RT40.9636 in0.9598 in
Jan 16, 2023UT Grid + RT40.9636 in0.9547 in
Dec 28, 2019UT Spot40.9677 in0.9561 in
Jun 25, 2018UT Grid + RT40.9724 in0.9641 in
Nov 26, 2016UT Spot40.9754 in0.9670 in
Dec 21, 2014UT Grid (API 572)40.9818 in0.9795 in