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V-1018 — Wet H2S Gas Drum V-1018

Delayed Coker · Wet H2S Gas service · Installed Aug 24, 2018 (8 yrs in service)

Medium
Current Min. Thickness
0.486 in
t-min 0.439 in
Measured Corrosion Rate
2.18 mpy
ML-predicted: 5.13 mpy
Remaining Life
21.7 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-240-316L Stainless
Design CodeASME BPVC Section VIII, Div. 1
Joint Efficiency1.00
Design Pressure329 psig
Design Temperature277 °F
Operating Pressure264 psig
Operating Temperature249 °F
Diameter44 in
Nominal Thickness0.524 in
Corrosion Allowance0.0625 in
H2S / Chloride145 / 214 ppm
Flow Velocity17.8 ft/s
Process pH7.55
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
5.14 mpy
Predicted corrosion rate under these conditions (+2.96 mpy vs. current measured rate)
Implied Remaining Life
9.2 yrs
Implied Reinspection Interval
4.6 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 + RT80.5052 in0.4859 in
Nov 15, 2025UT Spot80.5098 in0.4969 in
Oct 30, 2023UT Grid + RT80.5132 in0.5042 in
Oct 3, 2020UT Grid (API 572)80.5193 in0.5152 in