Question 24 3AE02 - Third Assistant Engineer (Alt)

The Correct Answer is A ### 1. Why Option A is Correct **A) Replace all of the packing rings.** When repacking a stuffing box, particularly one fitted with a lantern ring (which relies on proper sealing geometry and pressure distribution), best maintenance practice dictates that **all** old packing rings should be removed and replaced with new ones. This ensures: 1. **Consistency:** All rings have the same compressibility and sealing effectiveness. 2. **Proper Seating:** New rings conform correctly to the gland, the shaft, and each other. 3. **No Contamination/Wear:** Eliminates the possibility of damaged, hardened, or contaminated old packing rings interfering with the performance of new ones. ### 2. Why Other Options are Incorrect **B) Block off the sealing water connection.** The sealing water (or quench/flush) connection, which feeds the lantern ring, is crucial for lubrication, cooling, and maintaining a positive seal against atmospheric contaminants or shaft leakage. If the connection is permanently blocked, the packing will quickly overheat and wear out, leading to premature failure of the seal. **C) Be certain that all packing is fitted loosely to the shaft.** Packing must be properly compressed (by the gland follower) to create an effective seal. While excessive tightness is bad (causing friction and heat), fitting the packing loosely will result in immediate, uncontrolled leakage. Packing rings are designed to be slightly compressed against the shaft to function correctly. **D) For good lubrication, apply a fine grade lapping compound between the shaft and packing.** Lapping compound is an abrasive material used to polish or wear down surfaces. Introducing an abrasive material like lapping compound into a stuffing box would be catastrophic. It would aggressively wear grooves into the rotating shaft and quickly destroy the packing material, leading to severe leakage and expensive shaft replacement. Proper lubrication is achieved via the liquid being sealed or by the flush/sealing water delivered through the lantern ring.