The Design Of Packing Rings

Packing may be referred to as compression, automatic, or floating. Each term describes the type of operation in which the packing will be used.

Automatic and floating packings require no gland adjustments in controlling leakage. Automatic packings are confined to a given space and are activated by the operating pressure. Automatic packing rings are designed in the form of V rings, U cups, and O rings. Floating packing includes piston rings and segmental rings that may be energized by a spring. These types of packing are commonly used in reciprocating applications.

Compression packing is most commonly used on rotating equipment. The seal is formed by the packing being squeezed between the inboard end of the stuffing box and the gland (see Figure 1a). A static seal is formed at the ends of the packing ring and at the inside diameter of the stuffing box. The dynamic seal is formed between the packing and shaft or shaft sleeve. Under a load, the packing deforms down against the shaft, controlling leakage. Some leakage along the shaft is necessary to cool and lubricate the packing. The amount of leakage will depend on the materials of construction for the packing, the operating conditions of the application, and the condition of the equipment.

Packing must be able to withstand equipment variables (see Figure 1b). The design of the packing ring and the materials of construction must be resilient to follow shaft runout and misalignments, as well as to compensate for thermal growth of the equipment without an appreciable increase in leakage.

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Survival Treasure

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