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V-1025 — Sour Gas Overhead Column V-1025

Crude Distillation Unit · Sour Gas Overhead service · Installed Aug 25, 2013 (13 yrs in service)

Medium
Current Min. Thickness
1.662 in
t-min 1.543 in
Measured Corrosion Rate
0.50 mpy
ML-predicted: 0.99 mpy
Remaining Life
60+ 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-516-70 Carbon Steel
Design CodeASME BPVC Section VIII, Div. 2
Joint Efficiency1.00
Design Pressure493 psig
Design Temperature627 °F
Operating Pressure281 psig
Operating Temperature582 °F
Diameter109 in
Nominal Thickness1.675 in
Corrosion Allowance0.0938 in
H2S / Chloride918 / 109 ppm
Flow Velocity5.3 ft/s
Process pH5.93
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
0.10 mpy
Predicted corrosion rate under these conditions (-0.40 mpy vs. current measured rate)
Implied Remaining Life
60+ yrs
Implied Reinspection Interval
10.0 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 + RT61.6694 in1.6617 in
May 3, 2024UT Spot61.6676 in1.6603 in
Jun 17, 2022UT Grid (API 572)61.6689 in1.6662 in
Jan 6, 2021UT Spot61.6719 in1.6588 in
Oct 29, 2017UT Grid (API 572)61.6711 in1.6665 in
Feb 5, 2015UT Grid + RT61.6738 in1.6600 in