In order to improve rupture discs
operating efficiency and service life, there
are 5 basic selection criteria’s: D oes the R upture D isc withstand
full V acuum ?
R upture D isc O perating R atio Rupture disc are required to be vacuum
resistant. In some cases, rupture disc need
an additional vacuum support, while in
others they withstand the full vacuum as its
standard condition. There are forward-acting
rupture disc and reverse-acting rupture
disc that doesn’t need an optional vacuum
supports and at the same time doesn’t
withstand full vacuum. Such discs are not
considered when the need for vacuum
resistance exists.
The rupture disc operating ratio indicates
the pressure at which the disc can be
operated, with a prolonged service life.
Operating ratio is gotten by dividing the
maximum operating pressure by the
rupture disc burst pressure. Rupture disc
selection with a higher than required
operating ratio will be a waste of revenue
and failure, but selecting a rupture disc
with a lower operating ratio than required
will cause reduced production and
frequent change outs. Rupture discs have
a recommended maximum operating
ratio of about 50-95 % depending on the
construction method and materials. They
should not be selected for applications
where it will be subjected to conditions
above the specified maximum operating
ratio. Therefore, any rupture disc that
does not meet the required operating
ratio requirements must not be
considered.
P hase A pplication
In selecting a particular rupture disc for
installation, its phase application must
be considered. This implies that gas
only discs should be used in gas only
conditions, because it may not open at
all under liquid conditions. For instance,
many reverse buckling discs are applied
in gas conditions; its opening is actuated
by the energy stored in the compressed
gas. And since liquids are incompressible,
stored energy due to compression is
not available. Therefore, all liquid only
discs are eliminated in this stage, if the
application is gas.
D oes the R upture D isc require
being non - fragmenting ?
Rupture discs used upstream of a
pressure relief valve are normally
specified to be the non-fragmenting
type. This is because, when the disc
fragments lodges in the relief valve, it
obstructs the valve from closing properly.
In some applications, it is advisable not
to contaminate the process with the
pieces of rupture discs. This is the case
in sanitary applications. If fragmentation
is not required for the application, all
fragmenting rupture discs should be
eliminated.
T he S oft C riteria
Once the final selection list is established,
this criteria is used to evaluate the final
suitability of a rupture disc design for a given
application. The most important point is
that, time intensive evaluations is carried
out on a smaller et of rupture discs suited for
the application. At this stage, the expertise
of the rupture disc manufacturer does not
really affect the final decision on the type of
disc design to use in the application. Such
soft criteria is previous plant history with
the rupture disc design in similar or same
applications e.g. Interchangeability, ease of
maintenance, cycle life etc.
T roubleshooting
Understanding the causes that make a
rupture disc to fail will help ensure that
they don’t fail. When the cause of a rupture
disc failure is unknown, it is imperative that
the disc manufacturer should be consulted
for further analysis. In order to prolong the
service life and high accuracy of rupture
discs, causes of its problems should be
determined.
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