Page 234 - Valve Selection Handbook

Rupture Discs 221

facturer. Specific relationships are derived by the manufacturer with each
lot of material.
Reverse-buckling discs are considerably less affected by temperature
than forward-domed rupture discs.

Heat Shields

Heat shields are designed to shield the process side of the rupture disc
from heat radiation, or heat radiation and convection. They must be
installed in a manner that does not interfere with the rupture disc operation.
A heat shield may consist of overlapping stainless-steel flats that per-
mit pressure to build up on both sides of the flats. On rupture of the disc,
flow folds the flats open. The heat shield may be supplemented by a
spool piece serving as a heat sink between the rupture disc and the heat
shield. Further heat shielding may be provided by mounting a second
heat shield to the other end of the spool piece.
The heat shield shown in Figure 6-2 is intended for the heat shielding
of graphite rupture discs. Upon bursting of the rupture disc, the heat
shield will fragment and be discharged. For this reason, the heat shield
cannot be employed in conjunction with a vacuum or back-pressure sup-
port that could be blocked by the fragments of the heat shield. This par-
ticular type of heat shield is suitable for dry gases only as moisture
absorption changes the density of the wool filling that could lead to the
collapse of the filling.

Rupture Disc Application Parameters

Rated burst pressure. The rated burst pressure, also referred to as the
marked burst pressure, is the average burst pressure that has been estab-

Fiqure 6-2. Heat Shield Consisting of Holder Filled with Loose Wool of Amorphoi
Silica Filaments, Intended for the Heat Shielding of Graphite Rupture Discs.
(Courtesy oflMI Marston.)