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V-1070 — Caustic Wash Column V-1070

Crude Distillation Unit · Caustic Wash service · Installed Aug 31, 1988 (38 yrs in service)

Low-Medium
Current Min. Thickness
1.238 in
t-min 1.212 in
Measured Corrosion Rate
1.29 mpy
ML-predicted: 1.45 mpy
Remaining Life
20.2 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-240-304L Stainless
Design CodeASME BPVC Section VIII, Div. 2
Joint Efficiency0.85
Design Pressure306 psig
Design Temperature468 °F
Operating Pressure181 psig
Operating Temperature337 °F
Diameter111 in
Nominal Thickness1.298 in
Corrosion Allowance0.0625 in
H2S / Chloride45 / 1190 ppm
Flow Velocity19.5 ft/s
Process pH5.72
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
3.17 mpy
Predicted corrosion rate under these conditions (+1.88 mpy vs. current measured rate)
Implied Remaining Life
8.2 yrs
Implied Reinspection Interval
4.1 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)61.2482 in1.2381 in
Apr 30, 2026UT Grid (API 572)61.2491 in1.2378 in
Aug 31, 2023UT Grid + RT61.2515 in1.2500 in
Mar 10, 2022UT Spot61.2550 in1.2515 in
May 11, 2019UT Grid (API 572)61.2589 in1.2499 in
Jul 5, 2016UT Spot61.2625 in1.2551 in
May 3, 2014UT Grid (API 572)61.2671 in1.2669 in
Mar 14, 2011UT Grid (API 572)61.2684 in1.2546 in
Feb 2, 2008UT Spot61.2720 in1.2585 in
Jul 22, 2005UT Grid (API 572)61.2785 in1.2677 in
Nov 4, 2003UT Spot61.2826 in1.2769 in
Jun 11, 2002UT Spot61.2819 in1.2625 in
Jan 12, 2000UT Grid + RT61.2874 in1.2753 in
Nov 29, 1997UT Grid + RT61.2841 in1.2816 in
May 25, 1996UT Grid (API 572)61.2861 in1.2820 in
Nov 10, 1993UT Spot61.2916 in1.2724 in
Dec 26, 1990UT Spot61.2925 in1.2841 in