In a pump stuffing box, which item is used to prevent air from entering without causing excessive heat and wear on the shaft sleeve?

• A. Prevent air from entering without causing excessive heat and wear on the shaft sleeve.
• B. Improve lubrication of the packing.
• C. Seal the stuffing box from leaking fluid.
• D. Cool the shaft.

Answer: (A)

In a pump stuffing box, air entering the packing can cause overheating and accelerated wear on the shaft sleeve. The component designed to stop that while keeping the packing well lubricated is the lantern ring. It sits between the packing rings and provides a lubricant feed into the packing, creating a lubricating film around the shaft. This film carries heat away and reduces friction, while the circulating oil helps push air out or prevents air from being drawn into the packing. So it both lubricates effectively and prevents air ingress, making it the best choice for this purpose. The other options describe related goals (more lubrication in general, sealing leakage, or direct cooling) but do not address preventing air entry while maintaining proper lubrication the way the lantern ring does.