21. A pump shaft that is bent or distorted should normally be __________.

A bent or distorted pump shaft should be replaced because deformation indicates structural damage and hidden stress that cannot be reliably restored. Marine engineering practice dictates replacement of damaged rotating parts to prevent misalignment, vibration, bearing failure, and potential catastrophic damage. Repair methods like welding or heat treatment alter metallurgical properties and compromise the original design strength, necessitating replacement with a satisfactory spare.