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V-1237 — Caustic Wash Drum V-1237

Hydrocracker · Caustic Wash service · Installed Aug 29, 1997 (29 yrs in service)

Low-Medium
Current Min. Thickness
1.022 in
t-min 0.892 in
Measured Corrosion Rate
0.50 mpy
ML-predicted: 0.45 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. 1
Joint Efficiency0.85
Design Pressure551 psig
Design Temperature440 °F
Operating Pressure442 psig
Operating Temperature365 °F
Diameter54 in
Nominal Thickness1.043 in
Corrosion Allowance0.0938 in
H2S / Chloride42 / 91 ppm
Flow Velocity2.2 ft/s
Process pH8.89
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 — Chloride Stress Corrosion Cracking (Cl-SCC)

API 571 §4.5.2

Cracking of austenitic stainless steel exposed to chlorides above roughly 140°F under tensile stress; not a thickness-loss mechanism.

Recommended inspection approach: Surface/near-surface NDE (PT, ECT) at susceptible welds and CUI-prone insulated stainless piping; chloride source control.

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)61.0412 in1.0221 in
Apr 5, 2026UT Grid + RT61.0406 in1.0404 in
Sep 19, 2024UT Grid (API 572)61.0422 in1.0371 in
Nov 9, 2022UT Grid (API 572)61.0414 in1.0299 in
May 19, 2021UT Grid + RT61.0363 in1.0314 in
Dec 22, 2018UT Grid + RT61.0410 in1.0252 in
Jan 7, 2017UT Grid (API 572)61.0427 in1.0354 in
May 1, 2014UT Grid (API 572)61.0422 in1.0227 in
Jan 29, 2012UT Grid (API 572)61.0396 in1.0313 in
Sep 8, 2010UT Grid + RT61.0433 in1.0353 in
Jan 7, 2008UT Grid + RT61.0461 in1.0452 in
May 14, 2006UT Spot61.0444 in1.0344 in
Jun 1, 2004UT Grid (API 572)61.0427 in1.0408 in
Sep 2, 2001UT Grid + RT61.0410 in1.0311 in
Nov 4, 1999UT Grid + RT61.0447 in1.0440 in