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V-1254 — Caustic Wash Column V-1254

Fluid Catalytic Cracker · Caustic Wash service · Installed Aug 24, 2018 (8 yrs in service)

Low-Medium
Current Min. Thickness
0.954 in
t-min 0.870 in
Measured Corrosion Rate
0.73 mpy
ML-predicted: 1.25 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-387-11 Cl.2 (1.25Cr-0.5Mo)
Design CodeASME BPVC Section VIII, Div. 1
Joint Efficiency1.00
Design Pressure292 psig
Design Temperature587 °F
Operating Pressure163 psig
Operating Temperature411 °F
Diameter105 in
Nominal Thickness0.978 in
Corrosion Allowance0.0625 in
H2S / Chloride23 / 1812 ppm
Flow Velocity19.2 ft/s
Process pH6.49
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
3.89 mpy
Predicted corrosion rate under these conditions (+3.16 mpy vs. current measured rate)
Implied Remaining Life
21.6 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 + RT60.9730 in0.9540 in
Nov 26, 2024UT Grid (API 572)60.9722 in0.9683 in
May 30, 2022UT Grid (API 572)60.9738 in0.9718 in
Oct 12, 2020UT Grid + RT60.9769 in0.9681 in