A compression packing seal is established by installing the packing ring set into the stuffing box. Then, the gland on the back of the stuffing box is tightened to compress the packing between the shaft and stuffing box wall. Once compressed, the packing expands, exerting a radial force to the sides of the stuffing box and against the shaft.　

Packing in a stuffing box)

　　Built-in lubricants are released from the packing as gland pressure is applied. These lubricants are particularly important during equipment startup.

　　Eventually, the process fluid, or an external flushing fluid, takes over the packing's lubricating function and provides a continuous film of fluid to reduce friction. Heat dissipates through the shaft, packing, pump housing and process fluid.

　　Built-in lubricants are gradually lost during pump operation, often requiring further gland adjustment. Gland pressure is regulated to provide the optimum lubrication to seal and prevent overheating. Over time, loss of the lubricant and wear of the packing rings contribute to gradual decreased effectiveness, leading to the need to replace the packing.

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