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V-1036 — Sour Gas Overhead Drum V-1036

Alkylation Unit · Sour Gas Overhead service · Installed Sep 1, 1987 (39 yrs in service)

Medium
Current Min. Thickness
0.330 in
t-min 0.149 in
Measured Corrosion Rate
0.50 mpy
ML-predicted: -0.94 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 Efficiency0.85
Design Pressure99 psig
Design Temperature266 °F
Operating Pressure85 psig
Operating Temperature172 °F
Diameter51 in
Nominal Thickness0.342 in
Corrosion Allowance0.1250 in
H2S / Chloride355 / 165 ppm
Flow Velocity11.6 ft/s
Process pH6.42
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
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 (API 572)40.3365 in0.3301 in
Jul 9, 2025UT Spot40.3390 in0.3332 in
May 9, 2022UT Grid (API 572)40.3364 in0.3343 in
Jul 1, 2020UT Grid + RT40.3337 in0.3213 in
Oct 11, 2018UT Grid (API 572)40.3369 in0.3186 in
Feb 8, 2017UT Grid + RT40.3397 in0.3303 in
Jun 12, 2014UT Grid (API 572)40.3368 in0.3316 in
Oct 21, 2011UT Grid (API 572)40.3379 in0.3263 in
Apr 13, 2009UT Spot40.3407 in0.3243 in
Nov 7, 2007UT Spot40.3398 in0.3350 in
Nov 26, 2005UT Grid + RT40.3375 in0.3316 in
Mar 12, 2003UT Spot40.3382 in0.3270 in
Apr 9, 2000UT Grid (API 572)40.3422 in0.3373 in
Jan 21, 1998UT Grid + RT40.3409 in0.3258 in
Jun 19, 1995UT Grid + RT40.3419 in0.3389 in
Feb 3, 1993UT Spot40.3407 in0.3345 in
Jun 6, 1991UT Spot40.3436 in0.3360 in
Jul 6, 1989UT Spot40.3409 in0.3258 in