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V-1233 — Caustic Wash Drum V-1233

Sulfur Recovery Unit · Caustic Wash service · Installed Aug 24, 2018 (8 yrs in service)

Low-Medium
Current Min. Thickness
0.755 in
t-min 0.602 in
Measured Corrosion Rate
0.50 mpy
ML-predicted: -0.46 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 Efficiency1.00
Design Pressure310 psig
Design Temperature325 °F
Operating Pressure221 psig
Operating Temperature265 °F
Diameter77 in
Nominal Thickness0.776 in
Corrosion Allowance0.0938 in
H2S / Chloride26 / 3591 ppm
Flow Velocity19.7 ft/s
Process pH8.25
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
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 Spot80.7747 in0.7548 in
Jul 3, 2025UT Grid + RT80.7749 in0.7690 in
May 29, 2023UT Grid (API 572)80.7754 in0.7588 in
Dec 7, 2021UT Grid + RT80.7777 in0.7685 in
Apr 23, 2020UT Grid + RT80.7717 in0.7702 in