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Diaphragms
are hermetically sealing flexible elements dividing two volumes
of interchanging dimensions, interchanging pressure, and usually
of different media. Outstanding feature of a diaphragm is its ability
to flex in both directions vertical to the sealing flange plane,
within predetermined stroke limits, flexing effected either by mechanical
actuation or by reaction to differential pressure. Flexibility and
stroke limits of a diaphragm depend on properties of material used,
its dimensions, and in the larger stroke ranges - on the extent
of pre shaping provided in its manufacture.
Important properties of diaphragms materials:
- Flexibility for dynamic function)
- Resiliance (for sealing function)
- Mechanical strength (for pressure resistance)
- Chemical resistance (for media exposure)
- Low permeability (for diffusion resistance)
These
properties must be maintained for longest possible duration within
the temperature range, under the differential pressures, and in
permanent contact with the media specified in accordance with application
conditions. Basic materials used under these aspects in the manufacture
of diaphragms are
- Elastomers
- Elastomer coated fabrics and for additional reinforcements
- Fabrics
- Metals
- Thermo and Duroplasts as well as
- PTFE (Teflon foil)
For
surface protection against extremely aggressive media. Dimensions
and if necessary three dimensional shape of a diaphragms must be
determined in accordance with specific criteria as to installation
and function and with due consideration to the limits set by material
characteristics and manufacturing technology.
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