When repacking a stuffing box fitted with a lantern ring, which of the following precautions should be observed?

Correct Answer: Option B — Replace all of the packing rings.

When repacking a stuffing box, it is critical to replace the entire set of rings to ensure uniform compression and sealing. Mixing old and new packing results in uneven pressure distribution, which leads to premature wear, excessive leakage, and potential damage to the shaft or sleeve.