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V-1305 — Sour Gas Overhead Vessel V-1305

Fluid Catalytic Cracker · Sour Gas Overhead service · Installed Aug 27, 2007 (19 yrs in service)

Critical
Current Min. Thickness
0.858 in
t-min 0.896 in
Measured Corrosion Rate
6.81 mpy
ML-predicted: 6.86 mpy
Remaining Life
0.0 yrs
Next Inspection Due
Feb 20, 2027
Interval: 0.5 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 Efficiency0.85
Design Pressure187 psig
Design Temperature748 °F
Operating Pressure152 psig
Operating Temperature667 °F
Diameter135 in
Nominal Thickness1.005 in
Corrosion Allowance0.0625 in
H2S / Chloride905 / 291 ppm
Flow Velocity5.0 ft/s
Process pH7.63
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
7.40 mpy
Predicted corrosion rate under these conditions (+0.59 mpy vs. current measured rate)
Implied Remaining Life
0.0 yrs
Implied Reinspection Interval
0.5 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 Spot80.8779 in0.8584 in
Jul 14, 2025UT Grid + RT80.8837 in0.8742 in
Jul 2, 2023UT Grid (API 572)80.8965 in0.8817 in
Feb 13, 2021UT Spot80.9149 in0.9034 in
Sep 20, 2019UT Grid + RT80.9199 in0.9067 in
May 31, 2017UT Grid + RT80.9393 in0.9225 in
Dec 28, 2015UT Grid (API 572)80.9491 in0.9349 in
Nov 25, 2013UT Grid + RT80.9622 in0.9448 in
Aug 29, 2010UT Grid + RT80.9857 in0.9826 in
Jan 15, 2009UT Spot80.9970 in0.9861 in