19 - Packing and Seals

Abstract

This chapter emphasizes packing and seals, which prevents leakage between the shaft and housing. Shaft seal requirements and two common types of seals, packed stuffing boxes and simple mechanical seals, are described in this chapter. The efficiency of all mechanical seals is dependent upon the condition of the sealing area surfaces. Mechanical seals offer a more reliable seal than compressed packing seals. Mechanical seal designs are referred to as friction drives, or single-coil spring seals, and positive drives. A mechanical seal's performance depends on the operating condition of the equipment where it is installed. The pre-installation equipment inspection includes the stuffing box space, lateral or axial shaft movement, radial shaft movement, shaft run out, stuffing box face squareness, stuffing box bore concentricity, driver alignment, and pipe strain. Mechanical seals are often chosen and designed to operate with environmental controls. Failure modes that affect shaft seals are normally limited to excessive leakage and premature failure of the mechanical seal or packing.