V-1108 — Vacuum Gas Oil Vessel V-1108

Catalytic Reformer · Vacuum Gas Oil service · Installed Aug 28, 2000 (26 yrs in service)

Low-Medium

Current Min. Thickness

0.895 in

t-min 0.841 in

Measured Corrosion Rate

2.19 mpy

ML-predicted: 3.50 mpy

Remaining Life

24.5 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 Efficiency0.85

Design Pressure250 psig

Design Temperature601 °F

Operating Pressure152 psig

Operating Temperature518 °F

Diameter103 in

Nominal Thickness0.958 in

Corrosion Allowance0.0625 in

H2S / Chloride10 / 59 ppm

Flow Velocity20.0 ft/s

Process pH8.63

InsulatedYes

Corrosion & Remaining-Life What-If

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

Operating Temperature518°F

H2S Concentration10 ppm

Chloride Concentration59 ppm

Flow Velocity20 ft/s

Process pH8.63

Insulated (CUI potential)

MaterialDamage Mechanism

Live Prediction — What-If Model

7.40 mpy

Predicted corrosion rate under these conditions (+5.21 mpy vs. current measured rate)

Implied Remaining Life

7.2 yrs

Implied Reinspection Interval

3.6 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 — Naphthenic Acid Corrosion

API 571 §4.2.10

Aggressive, velocity-assisted corrosion in high-TAN crude fractions, most severe 450–750°F; low-alloy/carbon steel is far more susceptible than Mo-bearing or 316 SS.

Recommended inspection approach: UT thickness at high-velocity/turbulent locations; feed TAN monitoring; consider alloy upgrade per API 571 guidance.

Inspection History

UT thickness readings, most recent first

Date	Method	CML Count	Avg Thickness	Min CML Thickness
Aug 22, 2026	UT Grid + RT	6	0.9021 in	0.8947 in
Mar 16, 2026	UT Grid (API 572)	6	0.9015 in	0.8982 in
Jun 1, 2023	UT Grid + RT	6	0.9100 in	0.8951 in
Mar 28, 2020	UT Grid (API 572)	6	0.9113 in	0.9037 in
Apr 20, 2017	UT Grid + RT	6	0.9212 in	0.9168 in
Sep 7, 2014	UT Spot	6	0.9235 in	0.9079 in
Sep 1, 2011	UT Grid + RT	6	0.9354 in	0.9345 in
May 18, 2009	UT Grid (API 572)	6	0.9385 in	0.9355 in
Feb 9, 2006	UT Grid (API 572)	6	0.9457 in	0.9377 in
Apr 20, 2004	UT Grid + RT	6	0.9478 in	0.9376 in
Feb 24, 2002	UT Grid + RT	6	0.9558 in	0.9506 in