FASTENING & JOINING
Inflatable seals are easier to use and more forgiving withmisalignedparts than more-common compression seals.
Bob PaughKen Sterry
Pawling Engineered Products
Pawling, N.Y.
Designing With Inflatable Seals - 7327 F
For enclosures and equipment
that rely on flexible
seals, in-
flatable
bladder-type
seals
might be a better choice than
compression
seals. They are
more forgiving of irregular or
misaligned mating surfaces,
which cuts manufacturing
costs and boosts sealing in-
tegrity. They’re also easier to
use by requiring less force, so
technicians don’t have to force
two components together for a
good
seal. Instead, they just
move the mating parts freely
into place and inflate the
seal.
The only downside is that the
inflatable part of the
seal, the
bladder, needs compressed air
to operate. But in many set-
tings, especially the factory
floor, compressed air is readily
available.Based on these advantages,
inflatable seals have long been
used for dry-bulk-handling
equipment and drug and food-
processing machines. But now
they can also be found in grow-
ing numbers on processing
equipment, industrial isolation
chambers, flood barriers, aswell as in ultraclean rooms and
chip fabs. They also found fa-
vor among engineers design-
ing high-end vehicles such as
aircraft, spacecraft, and
yachts. On yachts for example,
inflatable seals isolate holds
that contain jets skis, scuba
equipment, and other gear
from harsh marine environ-
ments. Besides keeping out
harsh environments, inflatable
seals can also help keep cold
things cold and hot things hot.
The first issue the engineerneeds to decide is in what di-
rection will the
seal expand.
Should it expand inward, out-
ward, or axially? Next, the engi-
neer needs to consider cross
section, air connection, reten-
tion, materials, and reinforcing
fabrics. And there are some
general issues with corners,
end treatment, and joining of
extra-long extruded
seals.
Let’s look at these issues one
at a time.
Inflatable
seals come in a variety of shapes and sizes and are being used ina growing number of industries, including drug and food processing and IC
manufacturing.
Edited by Stephen J. Mraz
