Closed
Written 8/8/26 by Ray Thibodeaux
EWO: EWO-31844
Finding
Gasket seating surface on the stationary tubesheet is scored across three pass-partition lands. Machine the face back to a flat, continuous surface.
Formal write-up
Title
E-301 Stationary Tubesheet Gasket Surface Repair
Cause
Mechanical damage
Findings
Radial scoring up to 0.045 in deep across the pass-partition lands, consistent with the previous bundle pull. Serration profile is gone over roughly 40 percent of the seating width. Remaining ligament thickness measured at four positions is above the minimum required.
Acceptance criteria
ASME PCC-1 Table D-3 · TEMA RCB-6
Measurements
Location: Land 1, 0 degDepth: 0.045 inFlange thickness: 3.62 in
Location: Land 2, 120 degDepth: 0.031 inFlange thickness: 3.64 in
Location: Land 3, 240 degDepth: 0.028 inFlange thickness: 3.63 in
Recommended options
- Option 1 (recommended): machine the full face to a flat finish of 125 to 250 Ra, then re-serrate. Restores the design seating surface within the existing corrosion allowance.
- Option 2: weld overlay the damaged lands and re-machine. Longer outage impact and adds a PWHT question the schedule cannot absorb.
Justification
The scoring exceeds the surface finish the gasket manufacturer requires for a seated joint, and the joint has leaked on two prior runs. Machining is inside the remaining corrosion allowance and returns the joint to its design condition without introducing weld metal.
Notes
Machinist confirmed the face can be taken down 0.060 in and stay above t-min.
RR complete (initial & date)
RT 08/19
