Chemical Engineering June 2016 - 43

other components and configurations
available for this family of disc,
but this configuration is the most
common (table 5).
Scored forward acting rupture discs
-1970s to present. scoring a prebulged
metal rupture disc with precision
tooling and specialized presses
creates an even greater level of control
over the burst pressure. scored, forward-acting
rupture discs usually have
a cross-shaped score on the dome of
the disc. this allows the disc to open
with four distinct petals, without fragmenting.
some manufacturers offer
0% manufacturing range as standard.
others offer -5% or -10% (table 6).
these discs also have operating ratios
as high as 90%.
Scored reverse-buckling rupture
discs -1970s to present. reversebuckling
rupture discs are pressured
on the convex side of the disc. this
puts the dome in compression until
the structure buckles. the disc does
not experience permanent deformation
until right at the point where the
dome buckles. this makes reversebuckling
rupture discs ideal for applications
that must operate close to the
burst pressure, or are subject to cyclic
loads. Modern reverse-buckling rupture
discs are scored to create a nonfragmenting
opening after the disc
buckles. Burst pressure is adjusted
by material thickness, dome height
and sometimes by a dimple added
to the dome. Most reverse-buckling
rupture discs resist full vacuum (table
7) without added support.
Putting it all together
When determining the maximum
operating pressure for a reasonable
service life, we must consider all of
the performance parameters together.
table 8 shows the net result
of several interacting factors. note
that the maximum operating pressure
is nearly 43% higher for the
highest performance rupture discs
when compared to the lowest performance
discs.
Premium scored rupture discs can
cost more than lower-performance
rupture discs, but as table 8 shows,
they can be operated reliably at much
higher operating pressures. the increased
cost of the rupture disc is
often recovered through higher production
rates and reduced downtime
due to premature failures.
n
Edited by Suzanne Shelley
Reference
1. ASME, " 2015 ASME Boiler and Pressure Vessel Code, "
ASME BPVC VIII.1-2015, Section VIII.
Author
Alan Wilson is senior field engineer
for Oseco, a manufacturer of
rupture discs and other safety
pressure relief devices (1701 W.
Tacoma, Broken Arrow, OK 74012;
Phone: 918-258-5626; Email:
awilson@oseco.com). He holds a
B.S. degree in mechanical design
technology from Oklahoma State
University, and an MBA from Oklahoma
City University. Wilson has been with Oseco for 27
years, serving as an engineering expert in research and
development, rupture disc analysis and ASME code. Wilson
has earned several patents for his contributions to
the Oseco portfolio, and sits on two ASME committees.
He has helped to design, build and teach training seminar
programs for the proper use, installation and specification
of rupture discs in onsite learning events for
chemical processing plants and others in the field. Wilson
was also on the first team to coordinate with television's
Mythbusters program, when they featured Oseco
rupture discs in the first of seven episodes, using them
to measure explosion intensity.
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