Inspection of Plugs, Holding Members, and Screws
Inspect all plugs for corrosion or mechanical damage on the seating surface. Make sure that the plug has adequate bearing surface in the header seat (i.e., that it does not sit too high or too low in the seat). The ears on the plugs sometimes crack from repeated use. Inspect the ears for such cracks.
Inspect the threads on all holding members and screws. Look for loose, worn, or sloppy threads. Check the fit of the holding member and screw by hand to detect dangerously loose fits.
Where plugs are equipped with thermocouple wells, inspect the wells for corrosion, erosion, or cracks.