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V-1225 — Caustic Wash Column V-1225

Sulfur Recovery Unit · Caustic Wash service · Installed Aug 24, 2019 (7 yrs in service)

Low-Medium
Current Min. Thickness
1.741 in
t-min 1.568 in
Measured Corrosion Rate
0.50 mpy
ML-predicted: 2.96 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-240-304L Stainless
Design CodeASME BPVC Section VIII, Div. 1
Joint Efficiency1.00
Design Pressure377 psig
Design Temperature711 °F
Operating Pressure211 psig
Operating Temperature480 °F
Diameter137 in
Nominal Thickness1.746 in
Corrosion Allowance0.1250 in
H2S / Chloride16 / 1405 ppm
Flow Velocity3.3 ft/s
Process pH8.62
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
4.88 mpy
Predicted corrosion rate under these conditions (+4.38 mpy vs. current measured rate)
Implied Remaining Life
35.5 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 Spot61.7451 in1.7406 in
Apr 9, 2025UT Grid (API 572)61.7420 in1.7365 in
Apr 30, 2023UT Grid (API 572)61.7422 in1.7297 in
Aug 5, 2021UT Grid + RT61.7417 in1.7369 in