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V-1033 — Caustic Wash Column V-1033

Crude Distillation Unit · Caustic Wash service · Installed Aug 27, 2004 (22 yrs in service)

Low-Medium
Current Min. Thickness
1.178 in
t-min 1.082 in
Measured Corrosion Rate
0.50 mpy
ML-predicted: 0.20 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 Efficiency1.00
Design Pressure317 psig
Design Temperature608 °F
Operating Pressure253 psig
Operating Temperature426 °F
Diameter122 in
Nominal Thickness1.202 in
Corrosion Allowance0.0625 in
H2S / Chloride22 / 2684 ppm
Flow Velocity10.9 ft/s
Process pH7.40
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 + RT81.1983 in1.1783 in
Mar 19, 2024UT Spot81.2050 in1.1908 in
Jun 12, 2021UT Grid + RT81.2011 in1.1954 in
Jul 8, 2018UT Spot81.1996 in1.1854 in
Apr 20, 2016UT Grid + RT81.2003 in1.1994 in
Jul 17, 2014UT Spot81.2000 in1.1872 in
Feb 13, 2012UT Grid (API 572)81.1996 in1.1899 in
Sep 12, 2009UT Grid (API 572)81.1999 in1.1984 in
Dec 5, 2006UT Grid (API 572)81.2012 in1.1948 in