I performed the inspection on one of our ships,
Found that the screw hole is much lower than the rigid hydraulic line.
In my opinion the finding on the H/C which did have chaffing on the hydraulic line is typically an example of Murphys Law (caught on the right time).
1. The screw which had been installed was too long.
2. Somebody has been leaning/standing on the rigid hydraulic lines causing them to bend a little downward causing the outer line to vibrate against the screw.
regards,
Dragstay.