Figure 7-12.—Backup ring configuration.
If only one backup ring is used, place the
backup ring on the low-pressure side of the
packing (fig. 7-13, view A). When a backup ring
is placed on the high-pressure side of the packing,
the pressure against the relatively hard surface of
the backup ring forces the softer packing against
the low-pressure side of the gland, resulting in a
rapid failure due to extrusion (fig. 7-13, view B).
When dual backup rings are installed, stagger
the split scarfed ends as shown in figure 7-14.
When installing a spiral cut backup ring (MS28782
or MS28783), be sure to wind the ring correctly
to ease installation and ensure optimum per-
formance.
When TFE spiral rings are being installed in
internal grooves, the ring must have a right-hand
Figure 7-13.–Location of a single backup ring.
Figure 7-14.—Installation of cut dual backup rings.
7-13
