Page 238 - Valve Selection Handbook

Rupture Discs 225

tially or fully collapse. When these conditions exist, the disc must be pro-
vided with vacuum supports such as those shown in Figure 6-4, or in spe-
cial cases, such as superimposed back pressure, with supplementary per-
manent supports as shown in Figure 6-5. These supports must fit closely
the concave side of the disc to prevent alternating collapsing and stretch-
ing of the disc. The deformation of disc manifests itself in a wrinkle pat-
tern identified as turtle backing, as shown in Figure 6-6, resulting in a
poor service life.
Figure 6-3 shows one of the discs after bursting in gas service. In full-
liquid service, the rupture disc may burst initially in a pattern as shown in
Figure 6-7 and open further with rising overpressure.
Figure 6-8 shows a solid forward-domed rupture disc for low-pressure
applications in which the thickness of the burst element is at the near
minimum. The seatings of the burst element are supported on both sides
by protective rings that carry on the concave side an integral vacuum

Figure 6-5. Permanent Back Pressure
Support to Supplement Vacuum Support.
(Courtesy oflMI Palmer Ltd.)

Figure 6-6. Wrinkle Pattern Identified as
Turtle Backing of Solid Forward-Domed
Rupture Discs Due to Alternate Reverse
Flexing and Stretching Against
Inadequate Support. (Courtesy of
Continental Disc Corporation.)