Page 243 - Valve Selection Handbook

230 Valve Selection Handbook

Figure 6-12. Slotted and Lined Flat Rupture Disc Used as an Environmental Seal for
Transport and Storage Tanks and Downstream of Pressure Relief Valves. (Courtesy of
Continental Disc Corporation.)

The rupture disc shown in Figure 6-12 is a low-cost pressure relief
device typically used as an environmental seal for transport and storage
tanks and downstream of pressure relief valves. The disc does not require
separate holders but can be mounted directly between class 150 flanges.
Variations are designed for vacuum relief only, or for pressure in one
direction and for maximum double that pressure in the other direction.
Highest operating ratio is restricted to 50%.
The rupture disc shown in Figure 6-13 is designed for overpressure
relief of low-pressure systems. The discs withstand full vacuum and may
be used in gas and liquid-full systems. Operating ratio of the disc is as
high as 80%.

Compression-Loaded Types

In reverse buckling discs, the fluid load acts on the convex side of the
disc. This loading puts the disc in compression.
The material property that determines the buckling pressure is the
Young's modulus. This property is much more constant and reproducible,
and also less affected by temperature than the ultimate tensile strength of
metals used in the construction of rupture discs. In addition, buckling
occurs at substantially lower stress level than rupture under tensile stress.
Reverse buckling discs must therefore be made of a considerably thicker
material than forward-domed rupture discs. Consequently, they are much