Wet Insulation Found at a Platform on a Running Column

Sequence:

1. Strip insulation in a window around the breach first - typically 12–24 in beyond the visible damage in each direction - before deciding more. Insulation removal is the examination: nothing meaningful can be concluded through saturated calcium silicate.
2. Grid UT over the exposed shell, not single readings: a minimum of a 3 in × 3 in grid or equivalent, dense enough to characterize a band of general loss and to catch localized pitting at the jacket breach. Add readings at the platform attachment welds and at any supports or small nozzles in the wet zone.
3. Profile radiography of the suspect band is a good cross-check where external UT access is obstructed by the platform grating or where internals limit access.
4. Visual for the mechanism, not just the loss: staining direction, insulation saturation, chloride content of the water (calcium silicate plus chlorides is an aggressive combination), and condition of the jacket above the platform where water enters.

Extent of removal: follow the finding. If the first window shows loss, expand until two consecutive windows are clean - CUI is rarely confined to the visible stain, and water tracks along the shell under the jacket. Record each exposed area as a new CML with its own baseline.

Note that 400 °F is at the upper edge of the carbon-steel CUI range; cycling through the wet range below the dewpoint keeps the mechanism active, so the whole steam-traced or cycling zone deserves attention, not just the platform.

No - not automatically. The finding is external, the vessel is not internally due for 4 years, and the prior internal inspection showed no internal loss. Scope is set by the damage mechanism, and this mechanism is on the outside.

What is compelled:

• Recalculate remaining life at the new CML from the measured thickness. With 0.480–0.500 in baseline and 0.330 in required, the vessel can absorb substantial loss, so the arithmetic will almost certainly allow continued service; run it before assuming so.
• Reset the interval to the lesser of half the remaining life or the Table 1 caps. If the measured loss is heavy, half-life may fall below 8 months and force action sooner.
• If the recalculated remaining life comfortably covers 8 months, document continued service to turnaround with supplementary external examinations in the interim (repeat UT on the new CML) and a work order for permanent repair at the turnaround.

Options other than 'do nothing':

• An on-stream inspection in lieu of internal is not the lever here - the issue is external, and any substitution still requires the inspector's determination that there is no reason to expect internal deterioration plus jurisdiction acceptance.
• If remaining life does not cover 8 months, the choices are: temporary protection (jacketing repair, coating, wrap) with monitored thickness, reduced operating severity, or an early shutdown.

The judgment being tested: do not convert a localized external finding into a full internal inspection, and do not let it run unmonitored either.

Who does it: a repair organization holding a valid ASME R certificate of authorization (or otherwise acceptable to the jurisdiction), working to its written quality program. The owner/user's API 510 inspector authorizes the repair before work starts and reviews it after; the inspector may not be employed by the repair organization.

Technical requirements:

• Welding per ASME Section IX: qualified WPS/PQR, qualified welders, consumables controlled.
• Design of the patch from the original construction code (the vessel is VIII Div. 1) - patch thickness, corner weld geometry, and reinforcement.
• PWHT evaluation: confirm from the original U-1 whether the vessel was post-weld heat treated. A patch weld in a vessel that required PWHT must receive the same treatment; if the vessel was not PWHT'd, the repair still needs an evaluation of thickness and heat input.
• NDE per the construction code and the inspector's plan: at minimum PT or MT of the patch weld, and radiography where the code or inspector requires it; the inspector may specify more given the patch sits near the head-to-shell weld.
• Pressure test per the construction code - for a shell patch weld the default is a hydrotest. Any omission must be justified in writing by the inspector on a code basis (small, non-structural weld with full NDE) and the basis recorded with the repair documents.
• Records: repair report, NDE reports, WPS/PQR references, and the updated thickness history in the vessel file, with the CML reset to the post-repair reading.

A lap patch is a repair, not an alteration - no change to design conditions - so jurisdiction concurrence is not triggered, but the inspector's authorization and documentation are.