Winda Beacon · Library
What is corrosion under insulation (CUI)? Corrosion on the outside of insulated pipe, caused by water that gets through the insulation and is held against the metal. Hover a balloon or a note, switch layers, or step through the notes.
Corrosion under insulation, drawing sheet 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 A A B B C C D D E E F F A A CLADDING INSULATION STEEL BORE 4 METAL TEMPERATURE: SEE GRAPH 1 1 6 3 2 5 LONGITUDINAL SECTION 12 O'CLOCK 6 O'CLOCK B 2 3 6 SECTION A–A t NOM. t REM. STEEL WALL 5 WALL LOSS, HIDDEN 2 WATER AGAINST STEEL 3 INSULATION, WET CLADDING DETAIL B SCALE 4 : 1 GRAPH 1 CUI RISK RANGES BY METAL TEMPERATURE HSE 2011 · CAO ET AL. 2022 FROM ABOUT 65 °C, CONSIDER CHLORIDE CRACKING ON AUSTENITIC STAINLESS STEEL · HSE 2011 HSE 2011 MOST CRITICAL 30 120 CAO 2022* RISKIEST 50 175 OVERLAP PEAK, ~50–120 °C 50 120 RATES AS REPORTED ≈0.5 mm/y AT 80 °C, C-MN STEEL, US DATA · HSE ≈1 mm/y, ONE CASE, 60–120 °C · CAO WHERE THE SOURCES STAND LOWER, NOT ZERO SOURCES DIFFER BOTH FLAG IT PEAK RISK SOURCES DIFFER LOWER WHILE HOT 0 50 100 150 200 METAL TEMPERATURE, °C * CAO ET AL. 2022, CITING NACE SP0198 AND API RP 583. RANGES ARE FROM THE TWO DOCUMENTS NAMED, NOT THE TEXT OF A PAID STANDARD; ENGINEERING DECISIONS NEED THE CURRENT EDITION OF API RP 583. REVISIONS REV DESCRIPTION DATE BY 0 FIRST ISSUE, FROM THE LIBRARY PAGE OF 2026-10-25 2026-10-26 BL NOTES STEP THROUGH 1–5 PLAY 1–5 1 WATER IN HSE 2011 · CAO ET AL. 2022 FROM RAIN, COOLING TOWERS, SPRINKLER AND DELUGE SYSTEMS, OR CONDENSATION. IT GETS IN THROUGH BADLY DESIGNED OR FITTED CLADDING, FAILED JOINT SEALANT, MECHANICAL DAMAGE, OR CLADDING NOT REFITTED AFTER MAINTENANCE. 2 LOW POINTS HSE 2011 · CAO ET AL. 2022 IT GATHERS ON THE UNDERSIDE OF HORIZONTAL RUNS AND ELBOWS, AT VESSEL BASES, PIPE SUPPORTS, NOZZLE CONNECTIONS AND DRAIN LEGS. DAMAGE IS OFTEN FOUND AT THE 6 O'CLOCK POSITION. 3 HELD HSE 2011 INSULATION LEAVES A SPACE AGAINST THE METAL WHERE WATER CAN SIT WITH AIR. MINERAL WOOL, FIBREGLASS AND CALCIUM SILICATE SOAK UP WATER EASILY; FOAM GLASS AND PERLITE TAKE UP LESS. 4 HEAT HSE 2011 · CAO ET AL. 2022 OPERATING TEMPERATURE HAS A STRONG EFFECT ON RISK, AND SWINGS BETWEEN RUNNING AND SHUTDOWN REWET THE INSULATION. SEE GRAPH 1, ZONE E5. 5 FOUND HSE 2011 · CAO 2022 · API RP 583 CLADDING HIDES THE STEEL, SO WALL LOSS CAN GROW UNSEEN UNTIL A LEAK (DETAIL B). INSPECTORS CUT SMALL WINDOWS, AS GOOD AS WHERE THEY ARE CUT, OR SCREEN THROUGH INSULATION: PULSED EDDY CURRENT, GUIDED WAVE, RADIOGRAPHY. 6 CHLORIDES HSE 2011 SOME CLADDING MATERIALS CONTAIN FREE CHLORIDES, AND COASTAL AND OFFSHORE SITES ADD MORE. THIS MATTERS MOST FOR AUSTENITIC STAINLESS STEEL. 7 OFFSHORE CASE BSEE 2018 JULY 2018: EXHAUST PIPING UNDER INSULATION BLANKETS ON A PLATFORM DIESEL GENERATOR HAD CORRODED THROUGH, IN PLACES SEPARATED COMPLETELY. LAYERS SELECT A LAYER TO SWITCH IT ON OR OFF CLADDING 0.70 INSULATION 0.25 STEEL 0.50 WATER 0.25 DAMAGE 0.50 DIMENSIONS 0.18 NOTES 0.25 ALL LAYERS ON WINDA BEACON · LIBRARY beacon.winda.ai/library/corrosion-under-insulation TITLE CORROSION UNDER INSULATION (CUI) INSULATED HORIZONTAL PIPE: SECTIONS, DETAIL, RISK RANGES DRAWN BEACON LIBRARY CHECKED J. ZHONG, EDITOR DATE 2026-10-26 DWG NO. WB-LIB-CUI-001 REV 0 SCALE NTS SHEET 1 OF 1 PROJECTION