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242 Valve Selection Handbook

which the graphite burst membrane is a replaceable component. The pur-
pose of this design is to achieve a greater economy of graphite. The
reverse pressure supports shown, however, reduce the available vent area
to approximately 50% of full-bore area.
The disc is mounted in a controlled depth recess. By this arrangement,
the installation of the disc is non-torque sensitive.

Reverse-buckling rupture disc of pure graphite. The disc, such as
shown in Figure 6-28, is made of pure graphite without the inclusion of
resin. For this reason, the disc can be used for chemicals and high tem-
peratures [typically 550°C (1000°F)] that would normally affect resin
impregnated graphite rupture discs. Because the discs are thicker than the
membrane of the equivalent resin-impregnated graphite rupture discs,
reverse-buckling rupture discs of pure graphite can easily be handled.
Discs for burst pressures above 1.2 barg (17.4 psig) will support full
vacuum. Below this pressure, an additional support may be required. For
burst pressures higher than 1.0 barg (14.5 psig), the burst tolerance is
plus/minus 5%.

Figure 6-28. Rupfure Disc Device with Reverse-Buckling Disc of Pure Graphite.
(Courtesy of IMI Marston Ltd.)

Rupture Disc Holders

The original disc holders were intended for metal rupture discs that
failed in tension. They consisted of two flat-faced flanges between which
the discs were clamped.