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Function of a Resilient Metal
Seal
The sealing performance of
resilient Metal Seals is based on a the relative
high specific contact load at the sealing line
generated by the compression of the seal to a
certain groove depth and a certain resiliency or
spring back of the elastic metal seal.
Typically resilient metal
seals are compressed 15-20%. As an example a 3,18
mm FH (free height) seal is compressed to
approximately 2,5 mm.
In the figure compression
starts at point A.
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Point B illustrates the maximum
groove depth. At this point the seating load already
passed 90% of its maximum. |
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Point C illustrates the minimum
groove depth, or the point where the seating load
reaches its maximum. Reducing the groove depth even more
and thus increasing the compression ratio can lead to
seal failure. |
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Point D: At this point the seals’
resilience overcomes the remaining (decompression) load,
this resilience is called springback. |
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Point E: Springback of the seal at
20% of the maximum load (Lmax) is the useful springback. |
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Point F: Springback of the seal at
zero load is total springback = elastic recovery of the
seal. |
Engineering
Development and Engineering
of new products is conducted in close
cooperation with universities. In house testing
equipment facilitates real hardware testing and
comparison with FEA results. The Oysterseal® in
our catalogue is one of the results of this
bespoken cooperation.
General Information
High Performance Seals for
extreme service conditions.
HTMS' resilient Metal Seals
are designed and produced to provide the
required tightness, when subjected to extremes
of temperatures, pressure and media.
HTMS metal seals are produced
from stainless steel or high temperature alloy
tubing, strip and wire.
Sealing Concept
The sealing performance of
resilient Metal Seals is based on a the relative
high specific contact load at the sealing line
and a certain resiliency or spring back of the
elastic metal seal.
The seating load and the
corresponding sealing line width, are a function
of the selected seal type, cross section,
material, material thickness and the alloy
properties itself.
Depending on the required
tightness and the media to be sealed, a specific
seating load will be required. Plating or
coating with soft, ductile material will provide
better sealing by filling up groove
imperfections. The seating load will make the
ductile layer to flow and fill up the groove
surface irregularities.
Resilient Metal Seals require
a controlled compression. Typically these seals
are installed in a machined groove, or the
compression is limited by a so called retainer
plate.
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General Properties
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Sizes: Diameters from 5 mm to 7 meter
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Cross section from 0,8 mm to 12,5 mm |
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Temperature: Cryogenic to +1100°C |
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Pressure: From ultra high vacuum to +500 MPa |
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Available in circular, race track, oval and other shapes |
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Excellent resistance to corrosion and radiation |
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Maintains elasticity or spring back over an extended
service life |
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Does not suffer from explosive decompression |
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Capable of reaching tightness better than 10–9 mbar.l/s |
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Radiation resistant |
Material selection
The application parameters
determine which material should be used.
Temperature and media are important aspects in
selecting the material.
HTMS offers materials such as
321 stainless steel, Inconel® and other high
temperature alloys.
Exceptions And Particular
Cases
Resilient Metal seals often
have to perform under extreme service
conditions. Standard solutions as found in this
catalogue may not always suffice this
requirements.
HTMS can alter the standard
design and materials to optimize seal
performance for a given application.
With high accuracy and backed
by FEA in cooperation with the University, HTMS
can adjust the seals' cross section, wall
thickness, selected alloys, ..., in order to adapt seal performance to the variables
in service.
Plating - Coating
In house platings or coatings
are applied to improve the sealing performance
of metal seals.
Depending on the required
tightness, the selected seal, the media to be
sealed and the condition of the mating surface,
a softer or harder plating or coating shall be
chosen. When temperature allows, either PTFE
coating or soft silver should be applied.
The soft layer, flows at seal
compression into the mating surface
irregularities and creates hereby the best seal
performance possible.
PTFE coating can achieve leak
rates around 10–6 mbar.l/s, measured with the
vacuum method.
Metal type plating, like
silver, indium, and tin to name a few, can
achieve leak rates better than 10–9 mbar.l/s up
to 10-12 mbar.l/s.
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