Metal profile gaskets0 pages

Metal profile gaskets

Solid metal flat gaskets are used in areas where, due to the
medium, temperature, pressure and/or permitted leakage
rate, soft-material or metal/soft-material gaskets are not
particularly suitable. They have proven reliable at low temperatures of -200°C as well as at high temperatures of over
600°C. They are used at pressures ranging from relatively
low to extremely high.

In convex gaskets on the other hand, the contact geometry
is such that it is self-sealing at high internal pressures. The
sealing diameter is retained and edge pressure is avoided.

The thickness of the seal and the sealing material are generally dependent on the flange surface and the operating
conditions. The better the flange surface in terms of surface
quality and evenness, the thinner the gasket that can be
used, e.g. 0.5 – 1 mm as a gasket in spinning nozzle fittings
or 2 – 3 mm for aluminium gaskets in heat exchangers.

To avoid flowing when loaded or even a destruction of the
entire gasket, narrow flat gaskets should be chambered if
necessary, as is the case with flanges with tongue and groove
faces. Even with a chambered specimen there can be damage to the gasket, particularly if the sealing material is sensitive to crevice corrosion. In this case, fitting in a groove can
actually be disadvantageous. In order to prevent damage to
the gasket, ensure that the maximum permitted surface pressure σϑ is not exceeded under any operating conditions.

It should be noted that soft metals (such as aluminium or
silver) need only relatively low surface pressures to become
deformed, harder materials on the other hand, particularly
steel, require high sealing pressure.

Gasket profiles

Profile

Cross-section

A1

To reduce the sealing surfaces of gaskets with rectangular
cross-section such as Profile A1, choose a convex crosssection shape. Information on this can be found in DIN 7603
at Form D.

Narrow gaskets are more heavily loaded at the same bolt
force and can flow when insufficiently stable, leading to a
loss of bolt load and leakages.

06

Profiles A7 and H7 are centred by the corresponding shape
of the flange e.g. male and female face joint. Gaskets of the
type Profile H9 and H15 can also be used as high-pressure,
high-temperature gaskets
with flanges with raised or flat
face flanges. The gaskets are
then centred on the bolts. Profile H15, with a loose centring
ring, is ideal for use with gaseous media and/or centring
ring with widths greater than
15 mm. Profiles H7, H9 and
H15 have an osculating radius
R which is determined by the prevailing surface pressure.

The absolute level of the sealing press capacity can be reduced by using narrow gaskets instead of wide gaskets or
harder metals galvanised with thin overlays of soft metal.
Coatings of copper, nickel, silver or tin up to a maximum of
100 µm will give significantly better sealing properties and
significantly lower deformation surface pressure σV. For the
stated flange surface roughnesses a coating thickness of
35 to 50 µm is sufficient.

Gasket profiles

Profile

Cross-section

A7
In metal profile gaskets, a line contact arises first. The bolt
loads are clearly lower compared to metal flat gaskets (Profile A1). With the rectangular profile A1, even a slight flange
twist can lead to sealing problems. The sealing diameter in
the middle of the gasket jumps to the size of the external
diameter, causing the leverage to be adversely affected. The
greater internal pressure also has a negative effect.

H7
H9
H15

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Metal profile gaskets

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