Siemens SITRANS FX300, Operating Instructions Manual, Page: 15 / 80

DEVICE DESCRIPTION
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SITRANS FX300
www.siemens.com/flow 06/2009 - SFIDK.PS.050.F2.02 A5E02100423
2.2.6 Dual seal
To cover the requirements of ANSI/ISA-12.27.01-2003 “ Requirements for Process Sealing
Between Electrical Systems and Flammable or Combustible Process Fluid ” Dual seal, a
membrane vent is integrated in the neck of the instrument. This vent works in the improbable
case of a leakage as an annunciation valve between the primary seal (Process) and secondary
seal (electronic compartment).
The sealing between the pick-up and the Flow tube is considered as the primary seal. Its
construction material is always the same as the Flow tube itself (e.g. Stainless steel 316L or
Hastelloy C22). Chemicals used for the process, going through the Flow tube, must be
compatible with the designated material.
By using the membrane vent as annunciation valve, all requirements for a dual seal device in
accordance to above mentioned standard, are fulfilled.
• It protects the electronic compartment against access by process media, due to possible
leakages.
• The leakage of the primary seal is visible.
Regular maintenance should be performed by the customer to ensure this Dual Seal notification
system is working properly or that there is no leak.
If a leakage is noticed:
Siemens customer service should be contacted for servicing or replacement of the meter.
1 Annunciation valve (Membrane vent)
MA_Siemens_Sitrans_FX300_R02_en_PRT.book Page 15 Monday, June 22, 2009 8:17 AM