Question 62 QMED01 - Junior Engineer

The Correct Answer is D **Why option D ("Tighten the packing in small increments while the pump is operating.") is correct:** To prevent overheating and scoring of the shaft (or sleeve) after repacking a stuffing box, the new packing must be allowed to seat properly while maintaining adequate cooling and lubrication. The heat generated by friction is the primary cause of damage. By tightening the gland in small increments while the pump is running, the operator controls the compression of the packing, ensuring a proper balance: enough compression to minimize leakage, but not so much that excessive friction and heat are generated. The leakage itself provides essential cooling and lubrication for the packing and shaft. This gradual, operational adjustment is the standard procedure for properly bedding in new packing. **Why the other options are incorrect:** * **A) Operating the pump slowly and applying oil freely to the shaft until the packing is properly seated.** While slow operation might reduce initial heat generation, applying external oil to the *exterior* of the shaft does not ensure proper lubrication *inside* the packing rings where the friction occurs. The necessary lubrication and cooling are provided by controlled leakage of the pumped fluid, not external oil application. * **B) Lubricate the lantern ring with cylinder oil before installing new turns of packing.** The lantern ring (or seal cage) is positioned to introduce an external sealing fluid or lubricant (if used) into the middle of the packing set. While some initial lubrication might be beneficial, lubricating only the lantern ring does not guarantee adequate lubrication and seating of all packing rings, nor does it address the critical issue of adjusting the gland compression while the pump is operating to manage heat. * **C) Tightening the gland in all the way and then backing it off slightly.** Tightening the gland "all the way" immediately compresses the new packing severely, leading to extremely high friction, rapid heat buildup, and almost certain overheating and scoring of the shaft before the packing has a chance to cool or seat. Even backing it off slightly afterward is often too late to prevent damage. Packing must always be tightened gradually.