Figure 7-12.—Backup ring configuration.If only one backup ring is used, place thebackup ring on the low-pressure side of thepacking (fig. 7-13, view A). When a backup ringis placed on the high-pressure side of the packing,the pressure against the relatively hard surface ofthe backup ring forces the softer packing againstthe low-pressure side of the gland, resulting in arapid failure due to extrusion (fig. 7-13, view B).When dual backup rings are installed, staggerthe split scarfed ends as shown in figure 7-14.When installing a spiral cut backup ring (MS28782or MS28783), be sure to wind the ring correctlyto ease installation and ensure optimum per-formance.When TFE spiral rings are being installed ininternal grooves, the ring must have a right-handFigure 7-13.–Location of a single backup ring. Figure 7-14.—Installation of cut dual backup rings.7-13
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