CONSIDERATIONS FOR THE USE OF DOUBLE DISC RUPTURE DISC ASSEMBLIES
Double disc or “back-to-back” configurations of rupture disc devices consists of two rupture discs installed within a holder comprised of three
separate components: 1) Base, 2) Mid-flange, and 3) Hold Down. See Illustration 1. Such configurations can be equipped with forward-acting,
reverse-acting, or a combination of forward and reverse-acting discs for special process applications. Double disc arrangements can also be
comprised of individual single rupture disc assemblies however these combinations may require specific testing and qualification to assure
proper performance
APPLICATIONS
A common application for use of a double disc assembly is to isolate the
upstream or “primary”rupture disc from sources of variable back pressure.
For example, this condition can occur when multiple rupture disc assemblies,
protecting multiple processes, discharge into a common header. If one rupture
disc assembly bursts, the resulting discharge into the common header could
subject the remaining rupture disc assemblies to a transient elevated back
pressure condition. The downstream or “secondary” rupture disc is selected to
withstand high back pressure events leaving the primary disc to burst within its
specified rating.
Another widely promoted application of double disc assemblies is within
processes containing corrosive, toxic, and/or otherwise valuable media with
the objective of reducing the possibility of leakage to the environment or loss
of valuable products. This concept is accomplished by monitoring the pressure
within the mid-flange volume to detect leakage through the primary disc
possibly resulting from cyclic fatigue, Sulfide Stress Cracking, or other forms of
deterioration and then subsequently replacing the rupture disc upon indication
of leakage. It is critical in this application that the pressure in the mid-flange
volume is actively and continuously monitored, and that replacement of the
disc(s) is accomplished immediately upon detecting any increase in pressure.
