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Why
Gaskets Are Used ?
 Gasket
are used to create a static seal between two
stationary members of a mechanical assembly and to
maintain that seal under operating conditions which
may vary dependent upon changes in pressures and
temperatures. If it were possible to have perfectly
mated flanges and if it were possible to maintain an
intimate contact of these perfectly mated flanges
throughout the extremes of operating conditions; a
gasket would not be required. This is virtually an
impossibility either because of:
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The size of the vessel and/or flanges
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The difficulty in maintaining such extremely
smooth flange finishes during handling and
assembly
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Corrosion and erosion of the flange surfaces
during operations
As
a consequence, relatively inexpensive gaskets are
used to provide the sealing element in these
mechanical assemblies. In most cases, the gasket
provides a seal by external forces flowing the
gasket material into the imperfections between the
mating surfaces. It follows then that in a properly
designed gasket closure, three major considerations
must be taken into account in order for a
satisfactory seal to be achieved:
1.
Sufficient
force must be available to initially seat the
gasket. Stating this another way, adequate means
must be provided to flow the gasket into
imperfections in the gasket seating surfaces.
2.
Sufficient
forces must be available to maintain a residual
stress on the gasket under operating conditions to
ensure that the gasket will be in intimate contact
with the gasket seating surfaces to prevent blow-by
or leakage.
3.
The selection of the gasket material must be such
that it will withstand the pressures exerted against
the gasket, satisfactorily resist the entire
temperature range to which the closure will be
exposed and withstand corrosive attack of the
confined medium.>>The
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