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V-1180 — Caustic Wash Column V-1180

Catalytic Reformer · Caustic Wash service · Installed Aug 29, 1996 (30 yrs in service)

Low-Medium
Current Min. Thickness
1.040 in
t-min 0.952 in
Measured Corrosion Rate
1.36 mpy
ML-predicted: 1.74 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-240-316L Stainless
Design CodeASME BPVC Section VIII, Div. 1
Joint Efficiency1.00
Design Pressure281 psig
Design Temperature600 °F
Operating Pressure230 psig
Operating Temperature498 °F
Diameter112 in
Nominal Thickness1.084 in
Corrosion Allowance0.0938 in
H2S / Chloride36 / 906 ppm
Flow Velocity21.9 ft/s
Process pH4.12
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
6.11 mpy
Predicted corrosion rate under these conditions (+4.75 mpy vs. current measured rate)
Implied Remaining Life
14.4 yrs
Implied Reinspection Interval
7.2 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 Spot61.0439 in1.0397 in
Aug 31, 2024UT Grid (API 572)61.0452 in1.0335 in
Mar 11, 2023UT Grid (API 572)61.0477 in1.0400 in
Dec 1, 2019UT Spot61.0513 in1.0414 in
Jan 20, 2017UT Grid + RT61.0572 in1.0387 in
Nov 6, 2014UT Spot61.0606 in1.0453 in
Jul 11, 2012UT Spot61.0662 in1.0472 in
Sep 6, 2009UT Spot61.0678 in1.0550 in
Jul 20, 2007UT Grid + RT61.0716 in1.0640 in
Feb 1, 2006UT Grid (API 572)61.0722 in1.0617 in
Dec 24, 2002UT Spot61.0730 in1.0659 in
May 6, 2001UT Grid + RT61.0785 in1.0642 in
Jan 22, 1998UT Spot61.0818 in1.0748 in