What can reduce the friction between the packing rings and the pump shaft?

• A. Silicone grease
• B. Graphite
• C. Oil
• D. Teflon

Answer: (B)

Friction between the packing rings and the shaft is minimized by providing a lubricant that can withstand wet, high-temperature pumping conditions without contaminating the fluid. Graphite acts as a dry lubricant, forming a thin film between the shaft and packing rings. Its layered structure lets surfaces slide past one another with less wear, and it remains stable in hot, wet service, does not dissolve in water, and won’t contaminate the pumped fluid. The other options don’t fit as well: silicone grease can interfere with packing materials and potable-water systems; oil can contaminate the water and wash out of the packing; while PTFE (Teflon) is a solid lubricant, graphite is the typical choice specifically for reducing friction in packing glands.