V-1238 — Coker Vapor Vessel V-1238

Alkylation Unit · Coker Vapor service · Installed Aug 29, 1998 (28 yrs in service)

Low-Medium

Current Min. Thickness

0.897 in

t-min 0.813 in

Measured Corrosion Rate

0.50 mpy

ML-predicted: 0.30 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 Pressure258 psig

Design Temperature151 °F

Operating Pressure230 psig

Operating Temperature96 °F

Diameter125 in

Nominal Thickness0.904 in

Corrosion Allowance0.0625 in

H2S / Chloride3 / 25 ppm

Flow Velocity18.1 ft/s

Process pH8.34

InsulatedNo

Corrosion & Remaining-Life What-If

Adjust operating conditions to see the live model-predicted corrosion rate and implied remaining life

Operating Temperature96°F

H2S Concentration3 ppm

Chloride Concentration25 ppm

Flow Velocity18.1 ft/s

Process pH8.34

Insulated (CUI potential)

MaterialDamage Mechanism

Live Prediction — What-If Model

0.95 mpy

Predicted corrosion rate under these conditions (+0.45 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 — Erosion-Corrosion

API 571 §4.2.13

Mechanical removal of protective scale by high-velocity flow or entrained solids, accelerating the underlying corrosion mechanism.

Recommended inspection approach: UT thickness at flow-direction changes (elbows, reducers); review process velocity against API RP 14E erosional velocity limits.

Inspection History

UT thickness readings, most recent first

Date	Method	CML Count	Avg Thickness	Min CML Thickness
Aug 22, 2026	UT Grid + RT	4	0.8993 in	0.8973 in
May 30, 2025	UT Spot	4	0.8980 in	0.8907 in
Nov 25, 2022	UT Grid + RT	4	0.9000 in	0.8829 in
Jan 14, 2020	UT Grid + RT	4	0.9010 in	0.8998 in
Dec 3, 2017	UT Grid (API 572)	4	0.9020 in	0.8917 in
Jul 20, 2016	UT Spot	4	0.9016 in	0.8882 in
Apr 30, 2014	UT Grid (API 572)	4	0.8995 in	0.8808 in
Jan 31, 2012	UT Spot	4	0.9027 in	0.8985 in
Nov 3, 2009	UT Grid (API 572)	4	0.9024 in	0.9020 in
Sep 18, 2007	UT Grid + RT	4	0.9044 in	0.9034 in
Mar 31, 2005	UT Spot	4	0.8992 in	0.8849 in
Jan 28, 2003	UT Spot	4	0.9025 in	0.8873 in
Jul 5, 2000	UT Spot	4	0.9026 in	0.8886 in