Flush Diaphragm Seal for Pressure Instruments FDS

Applications

The diaphragm seal is a pressure-transmitting, diaphragm-type device. The pressure signal is sent to the cooperating pressure measuring device (Wireless Pressure Sensor, Pressure Transmitter, Pressure Gauge) through manometric liquid filling the space between the separating diaphragm of the seal and the pressure measuring device. The diaphragm seal's role is to isolate the pressure measuring device from damaging impacts caused by either medium or installation:

Low or high temperature, increased viscosity, impurities;
Vibrations of the installation (remote diaphragm seal).

Recommended minimum measuring range (bar)

Direct Diaphragm Seal: 0.1 bar for all sizes;
Remote Diaphragm Seal (2m): 1 bar for DN50/2", 0.25 bar for DN80/3" and DN100/4"

Recommendations

The essential metrological problem at diaphragm seal operational use is an absolute thermal zero error, resulting from the
thermal expansion of the manometer liquid. The expansion effect must be compensated for with the separating diaphragm
flexibility.

To minimize this effect, it is advisable to:

Use capillaries as short as possible, in this way the volume of manometer liquid will be reduced
Maximum capillary length for DN50 / 2” is 10m;
Use the greater diameter seals to maximize the separating diaphragm flexibility;
Locate the capillaries in the places, in which the temperature fluctuations will be minimal.

Zero error from ambient temperature change

An additional zero error, resulting from temperature fluctuations in a medium, depends on the temperature gradient in the oil-based diaphragm sealing system. The error value is, in any case, significantly smaller than the error value shown in the table.

Temperature range of measured medium

- Maximum pressure for PN40 – 40 bar
- Maximum pressure for ANSI 150 – 150 psi
- Material of diaphragm and flange: 316Lss

Important: standard outlet capillary from flange:

Direct-mounted diaphragm seal - axial
Remote-mounted diaphragm seal - radial
Other configuration is avaliable on request

Special versions

- Other standard ANSI or DIN
- Filled with edible oil (medium temp. -10...150°C)
- Direct diaphragm seal for medium temp. over 150°C
- Others

Ordering Code

Direct Diaphragm Seal: FDS-Flange Size-0M
Remote Diaphragm Seal: FDS-Flange Size-Capillary Length-Mounting of Capillary-Type of Manometric Liquid

Flange Size: select DN50, DN80, DN100 or 2", 3", 4"

Capillary Length: 2M, 3M, 4M

Mounting of Capillary: AX (Axial, standard), RD (Radial, option)

Type of Manometric Liquid: DH or DC or AK