Medical Design Briefs - November 2022 - 32

" Cryogenic equipment OEMs are driven
to deliver the safest operation as well
as longest life and lowest cost of ownership
to their customers, " says Geof Brazier,
managing director of BS&B Safety
Systems Custom Engineered Products
Division. " The use of an integral assembly
maximizes
the
longevity,
proper
function, and trouble-free service of the
pressure relief technology. "
n Integrated Assemblies -
Rupture Disk Design
The most important considerations in
rupture disk device design are having
the right operating pressure and temperature
information along with the expected
service life, which is often expressed
as a number of cycles the device
is expected to endure during its lifetime.
Since pressure and cycling varies depending
on the application, each requires
a specific engineering solution.
Because user material selection can also
determine the longevity of rupture disks,
the devices can be manufactured from
metals and alloys such as stainless steel,
nickel, Monel, Inconel, and Hastelloy.
For a wide range of industries, it can
be important for rupture disks to have
a miniaturized reverse buckling capability
in both standard and exotic materials.
In a reverse buckling design,
the dome of the rupture disk is inverted
toward the pressure source. Burst
pressure is accurately controlled by a
combination of material properties
and the shape of the domed structure.
By loading the reverse buckling disk in
compression, it can resist operating
pressures up to 95 percent of minimum
burst pressure even under pressure
cycling or pulsating conditions.
The result is greater longevity, accuracy,
and reliability over time.
However, miniaturization of reverse
buckling technology presents its own
unique challenges. To resolve this issue,
BS&B created novel structures that control
the reversal of the rupture disk to
always activate in a predictable manner.
In this type of design, a line of weakness
is also typically placed into the rupture
disk structure to define a specific opening
flow area when the reverse-type disk
activates and also prevents fragmentation
of the disk petal.
Small nominal size rupture disks are
sensitive to the detailed characteristics of
the orifice through which they burst.
This requires strict control of normal
variations in the disk holder. Due to cost,
weight and other considerations, Brazier
says that BS&B has increasingly received
more requests for housings that are
made out of plastics and composites.
Because customers are often accustomed
to certain types of fittings to integrate
into a piping scheme, different connections
can be used on the housing.
Threading is popular, but BS&B is increasingly
utilizing several other connection
types to attach the rupture disk assembly to
the application. Once the integral assembly
leaves the factory, the goal is that the set
pressure cannot be altered.
While OEMs have relied on rupture
disks in their cryogenic equipment,
the availability of integrated, miniaturized
rupture disk solutions tailored to
the application in a variety of standard
and exotic materials can significantly
enhance equipment safety, compliance,
and reliability even in extreme
work conditions.
This article was written by Jeff Elliott, a
Torrance, CA-based technical writer. For
more information, visit www.bsbsystems.
com. Contact BS&B at 918-622-5950 or
sales@bsbsystems.com.
Tough Gel Adhesives for Wound Healing
The strong, stretchy
hydrogel adhesives can
seal wounds almost
anywhere in the body.
Harvard Wyss Institute
Boston, MA
A Band-Aid® adhesive bandage is an
effective treatment for stopping external
bleeding from skin wounds, but an
equally viable option for internal bleeding
does not yet exist. Surgical glues are
often used inside the body instead of traditional
wound closure techniques like
stitches, staples, and clips because they
reduce the patient's time in the hospital
and lower the risk of secondary injury/
damage at the wound site. An effective
surgical glue needs to be strong, flexible,
and nontoxic, and it must be able to accommodate
movement, yet there are no
adhesives currently available that have
all of those properties. Researchers at
32
Inspired by the mucus secreted by the Dusky Arion slug, researchers at the Wyss Institute have developed a surgical
adhesive that can adhere to wet and dynamic surfaces inside the body, including the heart, lung, tendons, cartilage,
and bone. (Credit: Wyss Institute at Harvard University)
the Wyss Institute have developed a new
super-strong hydrogel adhesive inspired
by the glue secreted by a common slug
that is biocompatible and flexible and
can stick to dynamically moving tissues
even in the presence of blood.
www.medicaldesignbriefs.com
The hydrogel itself is a hybrid of two
different types of polymers: a seaweed
extract called alginate that is used to
thicken food, and polyacrylamide, which
is the main material in soft contact lenses.
When these relatively weak polymers
Medical Design Briefs, November 2022

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Medical Design Briefs - November 2022

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