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V-1124 — Wet H2S Gas Vessel V-1124

Catalytic Reformer · Wet H2S Gas service · Installed Aug 28, 2000 (26 yrs in service)

Medium
Current Min. Thickness
0.836 in
t-min 0.803 in
Measured Corrosion Rate
1.94 mpy
ML-predicted: 2.62 mpy
Remaining Life
17.0 yrs
Next Inspection Due
Feb 17, 2035
Interval: 8.5 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 Efficiency0.85
Design Pressure170 psig
Design Temperature457 °F
Operating Pressure107 psig
Operating Temperature406 °F
Diameter142 in
Nominal Thickness0.899 in
Corrosion Allowance0.0625 in
H2S / Chloride310 / 51 ppm
Flow Velocity1.1 ft/s
Process pH7.33
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
1.80 mpy
Predicted corrosion rate under these conditions (-0.14 mpy vs. current measured rate)
Implied Remaining Life
18.4 yrs
Implied Reinspection Interval
9.2 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 + RT80.8504 in0.8362 in
May 1, 2026UT Grid (API 572)80.8522 in0.8333 in
Aug 15, 2023UT Grid + RT80.8509 in0.8341 in
Nov 1, 2021UT Grid (API 572)80.8579 in0.8379 in
Aug 15, 2019UT Spot80.8603 in0.8504 in
May 5, 2016UT Spot80.8714 in0.8655 in
Jul 19, 2013UT Spot80.8764 in0.8611 in
May 10, 2010UT Spot80.8794 in0.8771 in
Aug 30, 2008UT Grid (API 572)80.8833 in0.8779 in
Aug 16, 2005UT Grid (API 572)80.8896 in0.8867 in
Jul 7, 2003UT Spot80.8956 in0.8948 in